QR codes

 QR codes  are 2D barcodes that have had a mixed success with usability, from nearly ignored (see the Tumblr mocking this), to partially successful (Path add friend UI), to invisibly useful (Snapchat add friend UI). See also examples of profile pictures with indieweb QR codes like http://aaronparecki.com/uploads/aaronpk-qr-code-avatar-20151005-174225.png and http://research.swtch.com/qr/show/a32975b9627fa8bc

General Criticism
QR Codes: bad idea or terrible idea?

Opaqueness Encourages Domain Squatting
Since QR codes are opaque to the user in terms of what URL is being navigated to, there is more incentive for nefarious domain squatters to take over expired domains that QR codes point to, e.g.:


 * 2015-06-19 Heinz QR porn code too saucy for ketchup customer "Heinz has apologised after a QR code on a bottle of tomato ketchup directed people to a pornography website […] the registration of the URL had lapsed because the related promotion had ended. The site is no longer live.""Graham Cluley, an online security expert, said: 'QR codes can point to anywhere on the web. The problem is that humans don't have a clue where they're going to be taken because their brain can't read a QR code, like they can a regular URL. 'It seems [Heinz] failed to renew their registration of the domain name, so it slipped out of their hands and was snatched up by an opportunistic porn site."

Broken links if you link to content you don't control
A River Plate fan just took the tattoo game to the next level with a QR code that shows the Copa Libertadores final goals against Boca Juniors whenever you scan it with your phone. Argentinian football fans are something else.
 * 2019-04-11 @MHChehade

...

Bad news to this River Plate fan as the video of the goals has been taken down off youtube due to copyright issues, his tattoo is basically just a meaningless barcode now. http://youtu.be/H2Apg8TmTYs

Generating QR codes
In a post describing the usefulness of QR codes in certain circumstances, mentions the Google Chart API, an open API to create QR codes - along with the concern that it may be shut down at any time.

For self-hosting, the open source PHP library PHP QR Code can be used to generate QR codes locally. uses it to include QR codes of URLs in the print view of his content, in order to enable easy interaction for readers of the printed version (code snippet)

capjamesg
has QR codes on his coffee map pages. These QR codes are available to make it easy for people to view the map on their phone. A map on one's phone is more convenient for someone who is on the move and looking to explore coffee shops.

Here are a few examples of these pages:


 * https://jamesg.blog/coffee/maps/edinburgh/
 * https://jamesg.blog/coffee/maps/york/

James generates the QR codes manually (see manual until it hurts). James has published QR codes on these pages since June 30th, 2022.

James also has QR codes for some of his social media profiles, aimed at reducing friction when sharing profiles in person. Examples include:


 * https://jamesg.blog/qr/github/
 * https://jamesg.blog/qr/instagram/