Weird
Optical Illusions
Illusion collections and perception demos. The good ones keep working after you have been told exactly how they work.
13 sites
The lab page of the psychologist whose completely static images refuse to stop rotating, added to for over twenty years.
- 10 min
- Desktop
Gianni Sarcone's workshop of puzzles and illusions, half optical trickery and half mathematical recreation, running since the 1990s.
- 10 min
Annual contest in which vision scientists compete to fool you, with every finalist since 2005 still watchable.
- 10 min
Plain, well-sorted illusion collection with the explanation directly underneath each one, from café walls to impossible triangles.
- 10 min
Interactive classroom illusions you can drag, toggle and pause, which makes the effects considerably harder to dismiss.
- 10 min
- Desktop
Tim Rowett's collection of optical toys and physics oddities, each demonstrated on camera by a man visibly delighted with all of it.
- 1 hr+
- Sound on
A philosophy department's catalogue of illusions, each with what it is, what it demonstrates, and the argument still going about it.
- 10 min
Catalogue of impossible figures, ambiguous objects and Escher-adjacent architecture, kept up by one very devoted collector.
- 10 min
The official Escher archive: the impossible staircases, the tessellations, and his own notes on how he worked them out.
- 10 min
Official home of the autostereograms from every 1990s shopping centre, with a fresh one each week to go cross-eyed at.
- 2 min
- Desktop
Around 140 visual phenomena, each with sliders to break the effect and a vision scientist's explanation of why you fell for it.
- 1 hr+
- Desktop
Long-running blog of illusions and visual puzzles, from classic ambiguous figures to whichever dress the internet is arguing about.
- 10 min
Steady feed of new illusions with the comments doing the debunking, which is usually half of the entertainment.
How we picked these
Every entry in Detour is hand-sorted rather than scraped: filed under one category, given one to three moods, and placed in a time band for how quickly it pays off. The practical facts — cost, sign-up, sound, device and whether it is safe at a desk — are recorded per site and shown on every card, so you can rule things out before you click.
Optical Illusions: questions
How many sites are in Optical Illusions?
13 sites, each hand-sorted by category, mood and how long it takes to pay off.
Which of these sites are free with no sign-up?
13 of the 13 are free and need no account. None of them are paid.
Do these sites work on a phone, and are they safe for work?
9 of 13 work on a phone; the rest are desktop only. 13 are safe for work and 12 work with the sound off.