qr codes

Veritasium builds a QR code by hand to explain how it works. It covers the history of Morse code and barcodes, how QR codes encode data, why damaged codes still scan, and how safe they are.

3Blue1Brown's discovery-oriented introduction to error correction codes, building up Hamming codes from the puzzle of locating a flipped bit. It explains the parity-check idea and why it is so efficient.

CGP Grey explains that postal codes are routing instructions for mail rather than geographic regions. He looks at the quirks and problems this causes.

CGP Grey explains why airport codes are inconsistent and sometimes confusing, from their origins in old weather station codes to the quirks that cause mistakes. He builds the story around a single typo that sent a flight to the wrong continent.

About Here explains how North American building codes requiring two staircases make small multi-story apartment buildings hard to build, and contrasts this with places that allow single-stair designs.