How do QR Codes Work? Features, Format, Error Correction, and More!

Quick Response codes (QR codes) are commonplace. They are highly recognizable and easy to use. But what is the format of that magic square? How do QR codes work? How are QR codes made? Why can you put a logo in the middle of a QR code? Please, let me explain!
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#garyexplains

[middleclasspoor]

Great vid! Thank you! I've been curious about QR codes, just not enough to actually look into them!

[christanner]

Another great, informative video. Thank you very much Gary!

[fllthdcrb]

6:09 Slight correction: larger QR codes have _more_ alignment patterns, placed at regular intervals horizontally and vertically.

Also, it's very interesting how even if there is damage to parts of the code you might think are critical, such as the timing pattern, it's _still_ readable with sufficient error correction, as your examples show. I'm not a big fan of putting logos and such in the middle, though; you're just throwing away some of that error correction and making scanning problems more likely. I would personally avoid it or at least try to keep it to a minimum.

[nboisen]

Interesting introduction to the formatting of a QR code. What would be interesting to learn is how a particular letter is encoded into a two-dimensional array of pixels. Maybe that could be your next video!

[bobanderson]

Great video, Gary. I've often wondered how these things worked. That information was most interesting, as I often find of your videos.

[gojohnniegogo]

Really helpful, Gary! I was just thinking about creating my own the other day as it happens. Cheers

[skyak]

Good video. I was kind of hoping it would go a little further into what happens when you scan these with your phone but it does make sense for that to be a separate video. Specifically, I worry these are incredibly vulnerable to man-in-the-middle attacks. I wonder if I could set my phone to use a super limited and secure DNS and antivirus on QR scan sites and maybe heuristics.

[markloughtonUK]

I've generated a few directly from Google Chrome (go to the share menu) and wondered how it still managed to work with their dino logo in the middle. Now i know. Thanks Gary !

[LokiDaFerret]

My phone reads your high quality error correction test with three red marks... "A QR code is a two-dimensional matrix barcode."

[paulbarnett]

I did wonder how they worked having the logos in the middle. They are just gaming the error correction to make it readable. Though that then makes it less robust for handling 'real' errors.

[logicalfundy]

Most restaurants in my area still use paper menus.

[tonysheerness]

Very interesting and informative. For some things they are fantastic but others it is technology for the sake of technology. I prefer a menu. in a restaurant.

[johnc]

Very interesting - thank you for researching it

[nimrodlevy]

This was amazing!! Many many thanks!!!

[djsbriscoe]

Could you please put the links to the QR code applications you mentioned in the description? Thanks.

[zz]

Awesome. Is there some mechanism to not have data on the middle (ie: blank), so that a logo on the middle isn't eliminating error correction altogether?

[Iconoclasher]

It's strange the "finder pattern" is as large as it is. It takes up about 20% of the area. A solid line along the top would accomplish the same thing. Assuming it's primary purpose is for orientation.

[philpots]

Well done Gary, I wrote UPC bar code software for a manufacture and learned that the white is the code and the black bars are the boundaries. I wonder if it's the same with QR codes?

[Fred-]

We went to a restaurant where you were supposed to scan a QR code to see the menu. Nope, sorry, it is too hard to read the 6-8 page menu on a 2.5" by 2.5" screen. We asked to get a real menu. Which they had but were trying to get people to avoid. Seems they thought the customers were supposed to serve the restaurant instead of the restaurant serving the customers.

For whatever reason, that restaurant has gone out of business.

[xinaesthetic]

There are some interesting AI images which are readable as QR codes but aside from the three orientation elements look wildly different...