I understand the code itself is a different make up of black/white grids to get your phone to recognize a linked site. But at some point won’t we completely run out of possible image combinations making them obsolete or is it something that regenerates a new site to QR connection? (On mushrooms so I might not have asked this very well lmao)
Basically will we run out of QR codes and if not how is there an endless supply?
This is partially correct. QR codes are a standard formated way to represent some data as an image of black and white squares. There is a data limit for what can be stored as a QR code so not all urls in existence are possible to be stored but most base routes are. Additionally you can store more than just a url. You can store various types of data. It just so happens that if you store the data for a string that is in a url format your phone is smart enough to recognize the URL format and redirect you to that url
There is a data limit for what can be stored as a QR code so not all urls in existence are possible to be stored but most base routes are
Well, the maximum length of URLs is "defined" as 2048 characters which is less than the maximum size of a QR code (around 3000 characters). So according to the specs QR codes can contain all "valid" urls.
However only MS Internet Explorer and Edge actually enforce that max length, other browsers and web servers have longer max lengths (anything from 4000 to 64000+). But because of Edge you'd probably still want to stick to less than 2048 for compatibility.
64000??? Are there any actual URLs that even get close to this length?
The querystring counts as part of the URL so if you wanted to upload a JPEG by base64 encoding the entire file into the querystring you could easily hit that ;)
MS Exchange has this "helpful" safelinks feature where every link in an email is replaced by another one, which sends the original link and some meta-information to Microsoft for espionage, eh, safety.
Take two sites using that feature. Send email from one to the other. Send email back. Repeat. (Not quite uncommon in a mail conversation, right?)
It doesn't take long until the links become too long for any browser to handle.
There's "data urls", which basically encodes the contents of the document into the url itself. Try pasting this into your browser:
data:image/jpeg;base64,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
Yea, one of the most common places on the internet people will encounter this is google image search. They serve the first couple rows of results with data urls so that the page loads all at once on the first paint instead of the page loading and then each image loading separately.
Google Amp links.
But a QR code has ~3000 binary bits, while a website has 2048 characters out of ~38 (~26 letters, 0-9 #s, and a couple special characters like _ or -). So there is a lot more variety of data in a URL string than a QR code.
The largest supported QR codes have ~3000 binary bytes, not bits.
2nd update: the first update was wrong, Update: Actually no. The QR code is binary. If there are 3000 spaces for dots, that’s 3000 bits.
Original: Yep thanks for that. Which still means there’s ~18x the data.
The largest QR code supported is 177 x 177 pixels. That's 31,329 "bits". When I said it was 3,000 bytes I wasn't kidding!
(Of course 31,329 bits is more than 3,000 bytes, the missing pixels are taken up by tracking marks and error correction).
Ok. Thanks for doing the math for me. :). Haven’t had coffee yet.
TBF you're a lot more likely to encounter a 54x54 QR code (3000 bits) than you are a 177x177, the extra capacity is just there if it's needed for some reason :)
Does that hold true with Edge using Chromium now? I would expect the default limits to be similar to Chrome.
All the online sources I see say Edge enforces the limit.
There was guy making a game binary small enough to be stored in qr code.
Is 2048 the max length for all URLs, or just http(s)? Can a data URL be longer?
Data urls are handled differently (not transmitted to the server) so they get a different, much higher limit. Potentially other external URL protocols like ftp:// have the same limit as http but recent browsers seem to have removed support for them...
around 3000
It’s 3072.
I don't think that's right, are you sure you're not thinking of the RSA 3072 encryption standard, which uses 3072 bit keys?
Yes. The QR code max size is 3KiB, which is 3072 bytes.
I think that's been approximated because if you look it up the maximum capacity of a v40 QR code is 2953 binary characters with low error correction.
Although possibly you can use "alphanumeric" encoding (not clear if that supports all the characters you'll find in a URL) giving 4296 characters with low error correction or 3391 with medium error correction.
It takes multiple binary digits to make a character. With 8-digit binary bites, that would be a 375 character limit.
You're thinking binary bits. "Characters" means entire 8 bit characters, so it's ~3000 bytes.
So a QR code has 24,000 pixels?
150 x 150? I guess that makes sense, but seems a bit high. Guess I learned something today
Max size is 177x177 (extra pixels are needed for tracking targets and word correction). You'll probably never actually see one that big though, most are as lot smaller. But if you really needed a ~3000 character URL it is supported...
Here's a very cool expansion, with multiple frames of animation, and multiple symbols per square, with multiple colors, allowing for pretty high information density.
https://github.com/sz3/libcimbar
Not made by me.
You can store various types of data
Yep. The ICU at the hospital I work in has QR codes in all of the rooms for some reason. The QR code just reads "ICU [room number]."
How do they use that? What do they scan QR codes for?
I honestly have no clue. I just scanned one one day to see what it came out as. Maybe it’s a charting thing.
I’m dumb, but could one increase the resolution of the QR code to fit more information or characters in the same space? Like, idk printing smaller to fit more words on a 3x5 notecard for example.
You could but technically but what you're describing is a new format. Even if you devised a way to encode more data no one's phone would understand the new format and be able to decode it. You'd need to get everyone on board with the idea for it to be useful. Alternatively, if you have some large amount of data you want to store. Why not create a download link to that data and then use the existing QR format to point to that download url
There exists different sizes for QR codes for more data but I think most devices just read the standard size. I'm not sure how resolution is handled
Ok well that answered that!
Side quest question: is it possible to run out of URL’s? 😂
Not really - like numbers, they just get longer. There are estimated to be about 10 to the power of 80 atoms in the universe - so an 80 digit decimal number would be enough to give every single atom in the whole universe its own unique number. That should be enough for... a while.
So what you’re saying is by the year 6000 we may be out of QR codes 🥲😔
If a million people generated unique urls every millisecond, it would take over 103567 years to use them all up. (Urls can right now be limited to about 2000 characters)
By then I think we won’t need them anymore.
Oh great, as if Y2K and Y2K38 weren't bad enough, now I have to worry about the Y103567 problem?
Edit: fixed superscript
Only if a million people generate unique URLs every millisecond for the next 103567 years. If one of them slacks of the job then we are fine.
Man let me tell you that will be the least of our worries then. Damn chihuahuas!
Maybe in a technical sense, but I dont think reusing a QR codes from a few thousand years in the past will be a problem
You can't "reuse" a QR code. It's not like a UPC which is assigned to an item in a database. A QR code is the data. It would be like "reusing" a book, with the same words in the same order, but somehow telling a different story.
The data encoded in a QR code is often an URL.
If I make a QR code today, linking to 'example.com/table_1',
I could reuse it tomorrow for a completely different purpose, simply by changing the content of 'table_1'
When you have been on the internets for a bit longer, you will also experience this effect:
Clicking on a bookmarked link will NOT take you to the ressource you used to rely on, but instead to a site serving pornography or gambling.
This has happened to a lot of the (now defunct) technical fora I used to frequent - some of the new owners have even made sites that look completely like the old ones (complete with fake updated posts in discussion threads) but with the purpose of infecting your system with spyware or crypto-lockers.
Let's stop thinking about the QR code as different from the URL. It's not. It's just a way for a computer to read a URL. Yes, you can change the content of the website it links to, but we know that.
The point is that we can't reuse a QR code in any way that is different from us reusing a permalink to a Reddit comment. That's all it is - a string of letters that takes us somewhere.
Certainly, but really not likely. That's like running out of addresses for houses. We just build more streets.
But eventually we run out of places to put streets big brain reply
Ah, but we just make the streets really tiny. Taps forehead
Or, hear me out, we just shrink humans so we need smaller calls for super tiny roads making up more room for houses also we will be shrinking the houses
You just invented Downsizing, which was a terrible movie and you should feel terrible.
Downsizing had some good parts. It just didn't know where it was going for the 2nd half of the movie.
What kind of fuck you give me?
I give you Love Fuck
“Get Them Out by Friday” by Genesis
Ha! And there’s subnetting lol.
URLs are also like addresses in that over time you can change what you put in them. It might mean the link/QR code/address book eventually doesn't work as intended, but they can be repurposed.
Then we just build vertically into the sky
No since you can make the world bigger so you can have bigger streets, which is the same as having a longer URL
I suppose this is roughly what the issue with running out of IPv4 addresses is, which is why there’s the very slow move to IPv6.
The thing about URLs and QR codes is : we can make them as large as we want. So we may eventually run out of 2-letter, 3-letter, 4-letter URLs and so on, but we can move on to 5 letter, 6 letter, 10-letter, 25-letter URLs.
Similarly, QR codes don't have a fixed size. They can expand to increase the amount of information written in them. If you need to put a bigger URL in a QR code, you can just increase the size of the QR code. So it's possible we may eventually use every single 10x10 block QR code, every 11x11 block QR code, every 12x12 block QR code and so on, but we can just move on to 15x15 blocks, or 20x20 blocks and so on.
This is different from IP addresses, which are limited because they have to be a fixed length. Every IPv4 address is a combination of exactly 4 numbers between 0 to 255, so there are exactly 232 IPv4 addresses available ever, so it's easily possible to run out of IPv4 addresses. In fact we've already reached the point where there really aren't enough of them and we've had to start using different hacks and workarounds to get things to work. It's also for this reason that IPv6 was added, which increases the number of possible addresses by several orders of magnitude, so that even though it's still limited, it appears unlikely that we'll ever get there. However, adoption of IPv6 is still very slow.
IPv6 is many orders of magnitude larger than IPv4. Something like septillions of available v6 numbers for every v4 number.
If every star in the observable universe had a thousand life bearing planets orbiting it, and each of those planets had a trillion people living on it, there'd still be more than enough IPv6 addresses available for everyone to connect their computers and phones and tablets and washing machines and whatever.
Latency would be pretty bad overall though unless we can solve that pesky speed of light limitation.
so there are exactly 232 IPv4 addresses available ever
There's actually fewer, because certain IP addresses are reserved for private network use (e.g. 192.168.*.* and 10.*.*.*) and some have special meaning, like 0.0.0.0 or 127.0.0.1.
Let's say URLs can be made of 64 allowed characters (a-z, A-Z, 0-9, %, / ). By the time you get to 45 characters long (6445 ) you have more URLs than atoms in the visible universe, so it would be impossible to store them all.
So we would run out of universe long before we run out of URLs!
This guy greps
Also 20+ years web developing and having to deal with base64 :)
I'm at 16 years! Had an early mentor push me toward linux and bash, which I'm forever grateful.
I like how you worded the follow up as a "side quest" question. Thanks for making my day a bit better.
It’s the least I could do my good sir
You’ll run out of IPv4 and IPv6 addresses long before you run out of URLs, not that they’re exactly the same
Let's see:
Characters valid for URL's: 0-9, a-z and A-Z, , so 26 +26 + 10 = 62.
URL Character Limit: 75 characters.
Possible combinations, 62!75 = 1.53***\**111*, that is, 1.53 followed by 111 zeroes.
Number of atoms in the universe: 10***\**78 to 10\******82*
So if we wanted we could give each atom in the universe more than a million unique URLs.
nah, we won't run out of URLs. it's like saying we'll run out of phone numbers but with the internet's equivalent of area codes and extensions. besides, if elon musk can keep coming up with new ways to tank twitter (or x or whatever), tech will always find a way around limits!
I think we're more likely to run out of phone numbers than we are to run out of URLs.
I guess a better analogy is like saying "We'll run out of subreddit names" or something along those lines.
A domain can be up to 253 characters, made of letters, numbers, and hyphens. So, 253 to the 37th power. Then the total URL (domain + path) can be up to 2,048 total characters.
So, while possible, it's not likely to happen in anyone's lifetime.
Is it possible to run out of words/sentences/numbers?
According to my 5 seconds of googling, the Oxford English Dictionary full version contains over 170,000 words.
So just to make the math easier, let's say 170k is the number of available words. Now let's just pretend that we're going to limit ourselves to three word groups. That's 1703 options, which is the same as 4.913 x 1015.
There's currently about 8 billion people on earth, which is 8 x 109. So our three word group rule leaves us with about 6 orders of magnitude more, so around a million combinations per person.
Now obviously, from a subjective standpoint, not every combination would be equally as desirable for various reasons, but there's still plenty to go around. And there's no real reason why you have to limit yourself to a group of three words either.
Also, not all URLs have to contain exclusively real words out of the Oxford dictionary.
I should have worded (hah) it better: can we run out of ways to group letters together?
Sure, but that just makes the numbers even bigger.
there's 26 numbers and then 10 letters, so that's 36 characters (special characters like punctuation marks and whatnot that can sometimes be problematic in URLS, so we'll just ignore them).
So just multiply 36 by itself however many characters long you're going to limit your URLs to. According to other comments, the max spec length for URLs is apparently 2048 characters so that'd be roughly 362048 possible URLs. That is an insanely large number.
There's estimated to be somewhere around 1080 particles in the observable universe.
To be honest, part of the URL is gonna be "reserved" for things like the https in front and the tld at the end, so more like 362036
Also, I would say dashes are quite ubiquitous in URLs, so I would up it to 372036.
Fair enough. Either way, I think we're pretty good on the url possibility space for quite a while.
QR supports something like 3500 characters. That’s a long-ass URL (and it doesn’t have to be a URL, it can be any plain text).
QR codes just encode strings of text, and for longer strings more black and white squares are used (meaning either the QR code gets bigger or the squares get smaller). The maximum amount of data that can be encoded allows for a few thousand characters. That would cover pretty much any URL you’d want to put on a QR code.
No, but we may run out of the URLs we want.
So the issue isn't really URLs but IP addresses. A URL turns into a IP address. So when I type in a URL it's actually in the background getting turned into something like 12.14.254.245. Right now we are running out of IPv4s which are in that format. IPv6 is a lot larger, so big it's highly unlikely we will ever run out.
URLs we'll likely never run out because I'm not even sure if there's a limit to the length of a URL, so you can always add more characters. youmightnotlikethatthisistheurlyouhavetotypein.com but it could be turned into a valid url.
Actually I will note I just looked it up. The limit to the length according to documentation is 2048 characters.
Just an FYI you don't need a unique IP address for every domain name (the first part of the URL), multiple domains can point to the same IP address then the server at that IP works out which website it should display.
But you do need a unique IP address for every publicly accessible computer/NIC, which is close enough to every domain name to be functionally equivalent. Coke and Pepsi, for example, would never want to host their proprietary websites on the same server, and they both have many subdomains, most likely with separate IP addresses.
For ELI5 it’s reasonable to say that we will run out of domain names when we run out of IP addresses. It’s close enough to being true that it’s not worth getting into the weeds about DNS, web server domain lookup, etc.
Yes, but one IP address can cover basically unlimited (obviously, computing power is an issue there) URLs thanks to SNI. So you can have an incredibly huge amount of URLs available with just two IP addresses (one for the server, and one for the client). Three, if you need a DNS server, too.
Is it possible to run out of words?
Will we ever run out of words? More or less the same question :)
Qr codes get bigger. I've put qr codes of entire essays in college. There's probably a limit but it's large
And qrcodes are extendable; bar codes are too.
If you set the maximum that a url can be at...let's say, 10 characters? You can extrapolate that as 3610, or thirty six to the tenth power--which equals 78,364,164,096 x 46,656. I've written it that way because the calculator tries to simplify the actual number. When you consider that most URLs have more than 10 characters, I think we're probably fine.
We would run out of IP-Adresses first. Every URL is just a key to get an IP adress from a special server, the DNS. When you tell your browser to get data from cornhub.com to get the latest news on your favorite crop, the Browser asks your router for the data from cornhub.com. your router then asks a DNS what IP Adress it has to ask for data from cornhub.com and if it gets an ip adress it can ask for the data, gets the hottest corn infos and sends it to your pc that shows it in the browser.
The shortage of IP Adresses is the reason why IPv6 exists. It can have more different adresses than IPv4.
Also, QR codes aren't necessarily a URL.
They can encode WiFi credentials (SSID and encryption settings)
They can encode vCards (name, phone number, email address, etc) or even just a standalone phone number or email address.
Or they can just be freeform text/data.
in fact, QR codes do not represent URLs, they represent text. that text can be a URL like "https://....." or a text like "hello world".
you can try it yourself with some online websites like https://www.qr.io
This doesn't really answer the question. A QR code is made up of white and black squares, potentially of different size. How many possible QR code combinations can there be?
Side question: there are multiple sites that let you create QR codes, so how do you ensure every generated QR code is unique such that you don't accidentally generate one that's already in use?
How many possible QR code combinations can there be
QR codes can be up to around 3,000 bytes long. That means there are 2563000 possible QR codes. As a comparison there are only 25634 atoms in the visible universe.
Side question: there are multiple sites that let you create QR codes, so how do you ensure every generated QR code is unique such that you don't accidentally generate one that's already in use?
To clarify my answer, the entire url is converted into binary then drawn as black and white pixels in the QR code. So the only way to get 2 of the same QR codes is to use the same URL. Different URLs will always generate different QR codes, because the whole URL is in there.
Theoretically then will the QR codes just get bigger?
In theory the maximum allowed URL length is smaller (2048 letters) than the maximum QR code size (3000 letters). MS Edge is the only browser that enforced that URL limit, but you'd probably want to stick to it for compatibility.
Also even with just 45 character long URLs there are a lot more possible URLs than there are atoms in the visible universe, so you'd run out of universe before you ran out of URLs!
3072, not 3000
What about those codes having information only and not URL etc?
Yep they can contain any data - anything from just numbers to full binary data. It just happens that their most common use these days is for automatic URL opening on smartphones.
What if the URL is very short, like x.com ? there won't be enough ones and zeroes to fill and entire QR box.
QR codes are variable length, that's why sometimes they seem a lot "denser" and have more of those little alignment squares.
It's not a 1 to 1 mapping, if data is shorter then smallest qr code it'll just add padding to make it fit exact space.
If you want this website goes through all the steps to encode example text https://www.thonky.com/qr-code-tutorial/data-encoding
The QR code represent the URL string. If the URL string is short then that's what the QR code represents. Now, if the QR code has more capacity than the information it stores, then the empty space is itself encoded.
That is incorrect. QR's aren't urls, they are just a string of data.
That's what she said!
Very ELI5 lmao
Because a QR code can contain anything QR scanners will probably need it to be in URL format (starts with http:// or https://) to actually launch a link from a QR code. Otherwise it'll just display it as text
Of course you can put ip4 or ip6 addresses instead of the domain. No reason onion address wouldn't work either, though maybe you'd have to copy and paste them if Tor isn't your default browser.
Think about a UPC code, those stripes you see on packages at the store. How those work is the thickness of the stripe encodes information, black lines are 1 and white lines are 0, so the computer scans it and sees something like 0001010100010101010110111010100101. That's just a number, and computers are good at taking numbers and looking on a list to see what the number is for.
The QR code is like a two-dimensional version of that same thing. Because it's 2D, they can pack more 1s and 0s into the same space, so it can include letters and other stuff instead of just numbers, which is why it's used instead of a really long bar code.
so it can include letters and other stuff instead of just numbers
Correct. I want to emphasize that "letters and other stuff" are also just numbers that were assigned to represent a symbol. With larger numbers you can represent more symbols. For example, you can chunk your bits into 8bit units (=1byte) and interpret those numbers (0-255) using the ASCII table, which contains 256 symbols including the digits 0-9, a-z, A-Z and the most common symbols like all the other characters on your keyboard.
That's awesome i've never thought of barcodes as being 1 dimensional before but I guess they are in a way.
It also helps (for me, anyway) to think about how the scanner shines a light (laser?) in just one stright line. The length of the bars is just for ease of scanning. The information is contained entirely by the width of the bars and the spaces between them.
That's also why you see some packaging get cute with their barcodes and print them in different shapes.
I was expecting something cuter. Like a female profile or something. I think they could have done something more with the idea.
You mean like these? https://www.demilked.com/most-creative-barcodes/
Yes! Thank you. I love them!
they literally are, not just "in a way". Theyre elongated into the second dimension to make it easier to hit it with a scanner, but the actual information is just 1 dimension
Think of it as reading in 1-dimension/direction, left to right versus left to right & up to down.
There are plenty of types of 1-dimensional barcodes that encodes both numbers and letters and other symbols. UPC isnt the only type of barcode. And depending on the type of barcode, the information can still be packed pretty compactly. UPC isnt a very efficient barcode format in terms of its encoding (it has low density), so it creates comparatively long strings compared to other more efficient/dense barcode formats. Code128 is a very dense barcode format which encodes all the 128 ASCII characters: https://en.wikipedia.org/wiki/Code_128
The most primitive QR code standard has 10132 possible combinations, which is 1052 times as many atoms in the observable universe. Since then, we have upgraded the standards to hold much more data. We will never run out of combinations.
Basically it doesn't looks like all that many dots but theres so many ways to rearrange them, it can in the simplest form represent thousands of characters.
You could try to come up with a string of letters it cannot represent but for practical uses you would never need to and most websites you visit will be in the tens of letters not the thousands.
My five year old kid wants to know what 10 132 is. Is it more than she has toys?
10132 is 1000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000.
It is approximately 10132 more toys than she has.
Edit: Missing a few 0's
My five year old has no idea what this means.
realistically neither do most adults, its unfathomable.
It's a bajillion. They'll understand.
Lol, I suppose that's fair.
Put another way, it is 1 million million million million million million million million million million million million million million million million million million million million million million toys.
Or 1 trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion toys.
There are about 31.6 million seconds in a year. If your 5 year old received a new toy every second since birth, right now they would have about 157 million toys. At age 100, they would have about 3.1 billion toys.
At the age of about 31689 years old, they would finally have about 1 trillion toys.
At the age of about 31689 trillion years old, they would have about 1 trillion trillion toys.
Keep multiplying by 1 trillion 10 more times. At the age of 31689 trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion trillion years old, they will finally have 10132 toys.
Still incomprehensible? Let's change things up a bit.
Receiving 1 trillion toys per second, you would be 31688764615412794009150320915288136746906210066214941214489649593879961565331173258130402181758768265324702412395 years old when you finally receive your 10132nd toy. Written another way, that's 31688 trillion trillion trillion trillion trillion trillion trillion trillion trillion years old. That's about 2.3 million trillion trillion trillion trillion trillion trillion trillion trillion times the current age of the universe. 1 trillion times less years than getting 1 toy per second.
As /u/GahdDangitBobby mentioned, there are about 1082 atoms in the universe, or 833 billion trillion trillion trillion trillion trillion trillion atoms. And 10132 is about 1052 times more than that. That's 333 billion trillion trillion trillion trillion times more than the number of atoms in the universe.
It is an incomprehensible number, and always will be.
age of about 31689 years
Daddy, are you that old?
It is an incomprehensible number, and always will be.
Indeed, there is no ELI5 for the age of the universe, or number of anything in it.
Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is.
So one thing to keep in mind: QR codes are just a way of writing something (such as a url to a website) in a way a computer can easily make sense of it reliably. That is to say, QR codes are not "linked" to anything, they're just a different way to write. You can use a QR code generator yourself to try it out and note same input always gives same QR code.
Now to answer your question, QR code combinations, that is to say, all the ways we can arrange the black and white squares to make unique messages, depending on standard, amount to more than there are atoms in the universe, so, in theory yes, in practice no.
Truly explained that so my 5 year old shroom curiosity is now at rest. Thanks!
So what is the advantage of a QR code vs. just having the URL printed out (and able to scan from a phone)?
While it may be much easier for you to read something written out in letters, it’s much much easier for your phone to read a QR code.
It’s the same reason we invented the original (one dimensional) barcode for supermarket scanners, rather than just having them try to “read” a numeric code.
If fast, accurate, cheap OCR scanners existed back in the day we might not have ever invented UPC/QR.
Even if we did there’s still some advantages to using upc/qr vs just OCR’ing human-readable info.
QR codes are easier for your phone to read and include damage corrections.
About 30% of the code could be destroyed and you would still get the full correct data.
the percentage is configurable
and that's exactly how people make qr codes with logos/art in them. that's not an inherent feature of qr codes. they're just using the error correction to make up for destroying part of the code with their picture
Can you provide more detail on the error correction?
Error correction in QR Codes works by adding redundant information to the encoded data using a Reed-Solomon error correction algorithm. This redundant information allows the QR Code reader to reconstruct the original data even if parts of the code are damaged or unreadable.
That's awesome. I've wondered how QR codes seem to hold up but never looked into it. Thank you!
Text is hard to read at an angle, if using wrong fonts and as soon as you cannot see one letter you cant access that url. Qr codes are built so that they don't have any such issue. They have built in corrections and dont need to be bigger to encode longer messages either
Error correction. As a scannable binary pattern the phone can check it got exactly the right URL. As regular text... "Wait, is that Google or Goog1e?" It's doable, but less robust, more error prone.
You can actually scan, copy and paste text including URLs now on iPhones - probably Android phones too, though I haven't tried - it works fairly well, but it's harder work for the phone and less reliable. If you want to put a "link" on your poster, truck or soda can, a QR code works better.
Reliably scanning text is fairly recent and still decently error prone. Scanning a QR code is basically the same tech as scanning a barcode and has been around for a lot longer. QR codes also have built in error correction, your phone is able to a) detect if it misread the code and b) potentially even correct any read errors on the fly.
I’d imagine you can capture a image from a further distance than a url, just a high guess lmao
QR code is more of an font than anything else. It doesn't link to anything. It's just a text written out in this specific "font".
You can use QR codes for many different things than just urls. You can have ones with text, image, game,....
You can fit in them about 4296 alphanumeric characters, so that should give you a lot of combinations.
I'm sure I saw a guy that encoded game code into a QR code itself, not just a link to the game. Pretty crazy what people can manage.
Also known for reverse engineering Lego Island, and ported apps to Windows 95 (back ported .NET Framework 3.5)
interesting that you mentioned images. obviously an image coded in binary would take up a lot of space, my phone actually has an app that uses a 24-bit version of QR codes for encoding image data as a 2d data array. much more space efficient but is a little less precise than the traditional 1bit codes.
Given an alphanumeric is pretty much ascii 8 bit you get ~4296 bytes - actually 2953 bytes per the format. That is ~3kb
To note: the Qr codes you typically see aren't as large as they can get since they don't need to be and work with worse cameras. QR codes can start to looks messy at QR40
QR can store arbitrary information. Small black squares represent 1, white squares 0. This way you can directly construct binary numbers from it. These binary numbers can be a text (see ASCII table that converts 2 digit hex number - which is 2x8 binary digits - to a single character like 'a' or 'X'). That's how you can encode an URL or any other text into QR code.
However, you and me, we can create our own system, e.g.:
0000 ...hello
0001 ...something bad happen
0010 ...I will come to you
0011 ...do nothing
0100 ...how are you?
0101 ...good
0110 ...bad
0111 ...afraid
...etc.,
and then we can encode a message (one or more of these) into one QR code. So - we can create an app for us that will take that text, convert it to those numbers & those numbers it will put into QR code. On other phone, the same app could scan the QR, get those number from it and then convert those back to the original text.
QR codes can be big and store a lot of information. See
https://en.wikipedia.org/wiki/QR_code#Design
Interesting thing is also that QR codes are immune to damage or imprecise reading by the camera. Simple idea behind error correction codes is that you put there some additional information that helps in guessing what was the original, i.e. let's encode just two words: "yes" and "no" like this:
00000 ...yes
11111 ...no
...then the message:
00100 00001 00111 11110 01001 10111
was probably "yes yes no no yes no". If you receive e.g. "00111" it is more likely that it was "11111" than "00000".
QR codes are just zeroes and ones, black and white that can be converted from binary to text. You can cover up some of the code because some of the bits in the image are for redundancy and you can use some fancy math to fix the code. There are different sizes of QR codes so you can fit more content in them.
It is basically just the link or any other piece of text as ones and zeroes plus some extra to repair the text.
Answering the "can we run out of qr codes" part.
Could we? Yes. How many combinations are there? Yes.
There are bigger qr grids, different encoding methods, different ways to do error correction... So you can create different qr codes that contain the same data after coversion.
There are also useless qr codes: like creating a code for the text AAAAAAAAAAAAAAAAAA. So there are millions of qr codes that are already wasted.
Or unreadable codes, imagine a checkerboard pattern. You can't read that (even if it had eyes and the 010101010 connecting lines between the eyes. Yes all qr have, by definition, lines of alternating black and white dots between the "eyes" of the code). A checkerboard pattern wouldn't have a header to tell the size, encoding and error correction used. There a million of patterns that would not result in a complaining qr code.
Yet, there's still millions of ways to create different URL addresses, presentation cards, mail addresses, WiFi info and all the other stuff a qr can contain like, even a game... https://youtu.be/ExwqNreocpg
Alphabet only has 26 characters, we're yet to run out of "combinations of letters" that are useful to us.
A QR code can store kilobytes of data.
Can we ELI5 what happens inside your phone when you open your camera app and it suggests the url? It’s a computer vision problem essentially. But it’s presumably looking for the corners and then determining the “bits” within that frame. Is there more to it? Does every phone use the same CV algorithm?
People are saying it’s just binary but if you’ve got a QR code which has a resolution of 25 x 25 (I.e 25 bits in a row that can be either black or white (1 or 0) that results in 500 bits, 62.5 bytes of data does it not?
Does the QR code architecture have some kind of built in data compression as well?
25 x 25 = 625
Did you mean 20 x 25?
The top answer is correct in every way but I’d like to add one more distinction. A URL can have arbitrary length. It can be as long as you like. Obviously you can only fit so many squares into a larger square so, given a specific version of a QR code, there are not an arbitrary number of them. As mentioned though, there are different versions. The most common is version 1, at 21x21. There are an obscene number of possible codes at even this size and we probably won’t run out of these any time soon. If we do, we can just use a larger version. Version 40, for example, is 177x177.
QR code is simply a "pixelised" version of a string of characters.
Basically you start with the string you want to put: HTTP://REDDIT.COM then convert that into binary. To do so, you use the ASCII table. This is a standard dating from the early computers that map each characters to a number. The result would be: 01001000 01010100 01010100 01010000 00111010 00101111 00101111 01010010 01000101 01000100 01000100 01001001 01010100 00101110 01000011 01001111 01001101.
You then add some more zero to fill up the space for the desired QR code size. You can't have unused space, so you fill it up.
Then you take that, and encapsulate it into the QR stuff, which add some more informations and length and also some error detection and recovery data. The error recovery and detection stuff add more bits that allow to detect and fix some of the errors. It do so by adding some redundant data and some cleaver stuff.
Now, you pass those 1 and 0 into some encoding scheme. Basically what it do is prevent too many of the same value to be in a row, for example (not sure of the exact encoding), it can say that if there is more than 3 of the same values in a row then you invert the next bit. So if you have 1111000 you get like 11100010. This prevent a long space that is all black or all white and help to figure out the bits.
And finally you generate the white and black dots, with the QR decoration stuff in the corners and center. The decorations in the corners are to identify the orientation of the QR code, so it read it the right way. Also, the decoration in the center actually destroy some of the data in the QR code, but that data is recovered via the error detection and recovery mechanism. It therefore reduce the reliability of the QR code, but since it work many do use it. It just mean that damage to some other places in the code will probably make it fail to decode, while it may have been able to be recovered if that center part was not there, as it would have more recovery data present.
So will you run out of QR code? No, because the code contain the information itself and is generated based on that, and is not an ID of some sort. And this is also why there is different QR code size, some contain little information, so can be small, others is huge because it contain alot of informations.
Note that a QR code is just a sequence of digits or characters (depending on type). They can hold a url, but they can also hold any text at all.
For fun, I once generated a QR code that was simply the text "Never gonna give you up, never gonna let you down, never gonna run around and desert you" and put up paper copies up in various coffee shops and such in my neighborhood.
QR code store information in the color of the dots.
Usually, some parts of the code are not meant to store information, but are used for alignment recognition. This is because your phone camera can captures the code under a wide variety of condition, like tilted, stretch out, flipped upside down, curved, etc.; not to mention it might captures something that looks similar to a QR code but is not. One way to do so: 3 corners have a fixed color pattern (not 4 because it will be hard to recognize the orientation); and the 4th corner also have a smaller fixed pattern (they all looks like boxes). But other variants are possible, due to many versions of QR code.
There might be also "dead" part of the code, such as the center, where people can put art work and whatever, which will be ignored by the phone.
Some other part of code tells you the version of the code, unrelated to the actual information to convey.
Both the actual information and the version are stored in term of binary: dark color represents 1 and light color represent 0. The dots have a pre-arranged ordering, so that your phone/computer can arrange these 0 and 1 into a single file of number. This string of 0 and 1 digits can then be used for a variety of application, but one common one is to encode an URL which can then be used.
Because the amount of 0 and 1 you can store is limited (if you make the dots too small it's prone to error), the string of letter cannot be too long: often the limit is 147 characters. For that reason, people who use QR code for linking to a website also combine it with an URL shortener. This is a service in which you can register a URL with a server on the Internet. This server will give you a short code for your long URL. To get to that link, you can use a shortened link, consisting of the server's domain name and just that code; then the server will see the code, retrieve the original link, and give it to your browser, and tell your browser to go there. The server's domain name has to be short as well, and this is something they can do by registering the domain to the registry. So, even though you can make the QR code "by hand", to use it for any actual purposes often requires additional set up.
This is sort of adjacent to OPs original question, but a fun fact about QR codes is that they use a form of error correction known as Reed Solomon encoding. There's a lot of really cool math behind how the error correction works and it's the reason why you can partially obscure a QR code and it will still scan correctly.
The short answer is "No, we won't run out."
Longer answer: there are multiple types of QR codes, but the smallest version holds 128 bits of information. 128 bits can encode 2128 ~= 3 × 1038 possible values. That's far more than the number of values humans are likely to conceive of in our entire existence. And even if a huge portion of them are unusable trash that's the smallest version. The largest versions of QR have thousands of bits; they could encode more values than will exist over the entire lifetime of the human race.
One way to think about it is that there are 26 letters in the English alphabet, yet lots of books have been written. With so few letters, how is it possible to write lots of books and not run out of letters? Much like letters and words are just a standardized way to represent language, QR codes are just a standardized digital representation of information.
Just high and you said books and letters not being finite made me think of this cool site. Everything that could ever has been or could be written. Quite fascinating.
Lmao, I actually just asked ChatGPT this a little bit ago. This is what they gave me:
The total number of possible QR codes depends on the version and error correction level of the QR code. The most common version, QR Code Version 40 (which is the largest standard size), allows for up to 177x177 modules (or squares), including the borders. Here's how you can calculate the total number of possible QR codes:
Modules (squares) in QR Code Version 40:
Possible module states:
Total possible combinations:
Let's calculate this:
[ 2{(177 \times 177)} = 2{31329} ]
This number is extremely large. For perspective, ( 2{10} ) is approximately 1,000, so:
[ 2{31329} \approx 10{9435} ]
This is an astronomically large number, meaning we have far more possible QR codes than we could ever realistically use. Even if every person on Earth generated a unique QR code every second for the entire age of the universe, we would still not come close to exhausting the number of possible QR codes.
There is no "big database" of QR codes, the code itself contains the URL.
Huh, good to know
Humans can communicate in different ways. For example, if we want to talk about a bird, we can write the word "Bird," use an emoji 🐦, or show a drawing or picture of a bird. All these things mean the same: Bird.
QR codes work in a similar way. They are like a special kind of writing that machines can read and understand.
The thing about QR codes is they aren't just a short code that links to the URL, they are the entire URL. It's the equivalent of converting the URL into binary and then drawing the resulting 1s and 0s as black and white squares.
Therefore as long as we don't "run out" of URLs we won't run out of QR codes.