How do QR codes work? (I built one myself to find out)

Special thanks to Mashiro Hara and Yuki Watanabe.

00:00 I was wrong
00:49 How Morse Code revolutionized communication
03:57 How barcodes work
10:34 How QR codes store information
18:16 Why damaged QR codes still work
29:54 Why are QR codes so common?
31:21 How safe are QR codes?
32:25 The future of QR codes

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Images & Video:
Cooke and Wheatstone telegraph patents via Wikipedia:

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Directed by Sumeet Kulkarni
Written by Sumeet Kulkarni and Derek Muller
Edited by Peter Nelson and Luke Molloy
Animated by David Szakaly, Fabio Albertelli, James Finnemore, Ivy Tello
Illustrations by Jakub Misiek, Emma Wright
Filmed by Derek Muller and Raquel Nuno
Additional Research by Gabriel Bean
Produced by Sumeet Kulkarni, Derek Muller, Rob Beasley Spence, Emily Lazard, Tori Brittain, Emily Zhang

Thumbnail contributions by Peter Sheppard, Ren Hurley, David Szakaly, Gregor Čavlović, Raquel Nuno
Additional video/photos supplied by Getty Images and Story Blocks
Music from Epidemic Sound

[jennalee]

God I love when I’m watching a YouTube video about the history of something and they bring on THE guy that did THE thing

[sano-keiko]

30:18 Correction: He said Tokkyo (特許 patent), not Tokyo.
The entire sentence is: We made the patent open to everyone, which made the QR code so popular.

[CockerelOfficial]

Veritasium: Here is how damaged codes work. It's pretty simple

Also Veritasium: Here's a 15 dimensional cube to explain this.

[MrBattlecharge]

Death was such a big motivator for change at the time. Another fairly well known example (atleast up here in Canada), is Joseph Bombardier, who invented the snowmobile. A snow storm rolled in and his kid was sick, Joseph couldn't go to the doctor or get any medicine. The child passed away, and Joseph dedicated his life to building the snowmobile and perfecting it.

[bigclivedotcom]

Darn! I knew QR codes were clever, but the error correction is mind boggling.

[ItIsJan]

I stopped watching for 2 minutes and we went from error correction to 5 dimensional hyper cubes

[mica_]

*Are you kidding me....* I just spent _two weeks_ researching how QR codes are made and implementing my own generator... and then days later you drop _this_, revealing all of my laboriously-gained arcane knowledge to the masses in half an hour.

[shaylennaidoo]

Honestly, if I could’ve had professors as skilled as you at teaching for my Comp Sci degree, I might have actually taken a genuine interest in stuff like this. Well done!!! ❤

[ExBlaz]

Error correction is the purest form of magic that I've ever come across in mathematics. It's like that children's trick where you take someone's birthday, add, subtract, multiply and divide it with some numbers and then guessing the original number from the result. That, but taken several steps further. It's honestly magical to me every time I think about it.

P.S. I was gearing up to write a 'long video but still no full form of QR' comment but you unexpectedly blindsided me with it at the end. Well played, good sir.

[mathITA]

For those that are convinced that SOS is an acronym a quick Wikipedia search explains that, originally (in 1906), SOS was chosen because is easy to remember and to read. The idea that it is an acronym for "save our souls" or even "save our ship" emerged years later as a way to help in remembering it.
Fun fact, this phenomenon in which a meaning is invented for a sequence of letter is called a backronym

[norlore]

You missed the opportunity to post the link to this video as a QR code on your community page

Edit: He did it let’s

[misterbrickest]

Derek, you really use the internet to make the world a better place. You're awesome and I've been watching you well over a decade. Every video is so well done. Congratulations on being such a great guy, using your passion to bring knowledge to the world.

Also: Amazing video! I've always wondered about QR codes. Now I know something about them and their history. The error correction part was also really interesting as I've always been amazed by the idea of correcting errors with only small amounts of additional data.

[jorusenpai]

The part in 30:18 where the translation of what Mr. Hara said was "We decided to launch it in Tokyo..." is actually「特許オープンにした」which means "made it an open patent..." So he actually said "We realized that it was the right thing to do when we made it an open patent. And as a result, it spread widely and we think that it's really good."

I learn so much from your videos Derek! Thank you so much!

[luca_]

2:00 “…Breese Morse…” what a strange na… OH HE’S THAT ONE

[pastek]

10:15 "In Go, you basically place stones at the intersections of lines"
12:40 Derek: mmh yes squares

[ryanio]

I love how the Version 40 QR code at 12:10 is a snippet of the script. Great way to put in an Easter egg.

[jaspermcjasper]

3:06 - Not only did real-time DEcoding of Morse Code come as a surprise to Morse and manufacturers, but real-time ENcoding wasn't anticipated either. There many things that nobody thought humans could do until humans were doing it. The original intent with Morse was that you'd use the codebook to translate the message's letters (and maybe some punctuation) into dots and dashes, then completely lay out the message using metal slugs (short ones for dots, long ones for dashes) in a rack or on a drum. With the message already composed, you'd step up to the wires and turn a switch that would turn on a slow-turning drum at the telegraph wires' other end.

That drum was coated with paper or something similar, and a pencil (or something similar) was pointed perpendicular to the drum's circular surface, towards the drum's axis. The switch's current also rang a bell at the receiving station, to tell someone to be sure to have paper on the drum for a soon-to-be-incoming message. The pencil was held by electromagnets (or something similar) so that with current applied (miles away), the pencil would be pressed into the paper on the drum, and when the current was interrupted, the pencil would rapidly retract.

Then the sender would run their rack (or drum) of dots and dashes over the contacts, which, miles away, completed the circuit around the pencil and caused it to write long and short marks (the dashes and dots), separated by empty white space, on the drum's paper. People at the receiving end would then use the code-sheet to change the drum's paper's dots and dashes back into letters.

At the time of Morse code's inception, nobody knew that the process of changing letters into dots-and-dashes at the sending-station and the process of changing dots-and-dashes back into letters at the receiving-station would soon be done without cheat-sheets by people who could do it entirely in their head, FROM MEMORY of the code-sheet, and IN REAL TIME, which made sending a Morse message more like talking back and forth and less like typesetting a broadside for a printing-press.

[DavidXian]

Indonesians are also really into using QR codes. They’ve even standardized QR payments with something called QRIS (with IS standing for "Indonesia Standard"; also a pun of keris, a traditional Indonesian weapon). What’s craaaazzyy about QRIS is that it accepts payments virtually from any bank and any e-wallet. At first, each payment provider had its own QR code, but now it's just QRIS everywhere. From minimarkets to restaurants, and even street vendors/peddlers on the roadside! It’s wild!

[ianmoore]

34:13 "They're called quick response because they react quickly."
The man is thrilled with his work :D

[studiosilisium]

A company in Norway called Piql fits 2MB of data into a QR code. They use it for super secure, long-term (2000 year) data storage. Pretty insane!