Ten minutes to kill

A breathing bubble with adjustable pace, sitting on a page that mercifully does not require the app to work.

Cut-out cats rain down and bounce off the bottom of the screen, and you can grab one and fling it at the others.

A free endpoint that returns one cat fact per request, which is how every cat-facts prank bot ever built gets built.

Anime avatar makers with genuinely good line art, including versions that output something usable as a profile picture.

Chess tactics training with a rating that goes down, plus an endgame trainer that reveals exactly how much you do not know.

The default chess address for most of the planet, with a bot for every skill level and puzzles that will quietly humble you.

A chihuahua rotating to a dance track, which was apparently a complete website idea in 2013 and somehow still is.

The offline dinosaur from Chrome's error page, playable while you still have a perfectly good connection.

Five photographs, one question each: what year was this taken? Points scale with how close you land, and the cars always give it away.

Renders every road in any city as white lines on black and nothing else, which turns an ordinary street plan into unexpectedly good art.

Paint over whatever is ruining a photo and it fills the gap convincingly. Free at standard resolution with no account.

Sixty seconds to forge the Mona Lisa with a mouse, then a pixel-by-pixel score telling you exactly how badly it went.

Curated stumble button that sends you somewhere good rather than somewhere random, with categories if you are feeling fussy.

Fill-in-the-blank sentences mined from real corpora, aimed squarely at people who have outgrown the beginner apps.

NASA ephemeris data, brutal one-line notifications and a design language everyone copied. Astrology delivered entirely deadpan.

Mash any keys and immaculate code appears on screen at speed. Enormously convincing to anyone standing more than a metre away.

The murmur of a café without the queue or the cost, built on research that moderate background noise helps creative work.

Hand-picked four-colour palettes posted daily and sorted by mood, with none of a generator's randomness.

Palette generator trained on photographs and films, so the colours it suggests look like they came from somewhere real.

Sixteen words, four hidden groups, four mistakes allowed. The traps are the entire point and they are very carefully set.

Generates hero images — gradients, particles, triangles, topography — at whatever resolution you need, free to download.

The site every school network forgot to block, still hosting Run 3, Fireboy and Watergirl and almost no actual mathematics.

Chrome, flames and bevelled gradients — the 2003 logo generator, still online and still producing exactly that.

Hit the space bar for a five-colour palette, lock the ones you like, hit it again. The whole tool is that loop.

Nest and feeder cams run by the Cornell Lab, with ornithologists in the chat explaining what the bird is doing and why it matters.

One button that adds unicorns and rainbows to any web page, solving a problem that has never once been reported.

Upload any file and receive a genuinely corrupted version back. Built for missing deadlines, used mostly for art.

The same premise with different flavours of damage — choose the format and how thoroughly you want it ruined.

The EFF's test showing how uniquely identifiable your browser is from fonts, plugins and screen size alone. Most people are one in millions.

The biggest browser arcade going, with genuinely decent HTML5 ports and a search that mostly finds the game you meant.

A few hundred browser escape rooms in one filtered shelf, all running in the tab with nothing to install and nothing to buy.

Translates a cron expression into plain English as you type it, then tells you when it will next fire. Ends a very specific argument.

Frogger with better manners: hop a chicken across roads, rivers and railway lines until the inevitable lorry.

Where every cruise ship in the world currently is, with deck plans and itineraries attached, for reasons entirely your own.

Chain encoders and classical ciphers together and watch text transform between formats at each step.

Builds a gradient visually and hands over the CSS, including the awkward multi-stop and radial cases.

Sugar-coated filler text for wireframes, with sliders for exactly how sweet and how long the nonsense should be.

Several hundred cipher, code and puzzle solvers in one place, from Caesar shifts to crossword pattern matching.

Fast browser shooter with no account and no download: click, spawn, and get eliminated by somebody considerably better.

Mix rain, keyboards, seagulls and a fireplace into one soundscape, then hand the whole mix to somebody as a single link.

A graphing calculator good enough that people make art with it — type a function and drag its parameters about.

Alarming research site about a chemical found in tumours, acid rain and every reservoir on earth. The chemical is water.

An avatar library where you can dial through a dozen illustration styles and copy the result straight out as an image.

A tank shooting polygons for experience, then branching down a surprisingly deep upgrade tree, from the maker of Agar.io.

Paste two blocks of text and get a colour-coded diff back immediately. Also handles PDFs, images and spreadsheets.

Turns any image into one-bit dithered grain, with a choice of classic algorithms and a two-colour palette picker.

Dithering aimed squarely at the chunky, ugly end of the spectrum, with palettes lifted from old hardware.

Runs a standard or extended check to reveal which servers actually saw your DNS lookups. The quickest way to catch a VPN not doing its job.