What's my JND? – a colour guessing game

In plain words

What's my JND? is a color guessing game that challenges players to identify subtle differences between similar colors. The game is designed for anyone interested in testing their color perception abilities. It focuses on JND (just noticeable difference), the threshold at which the human eye can detect variations in color, making it an interactive way to explore the limits of color discrimination.

written from the facts on this page · September 2026

From the sources

Find your Just Noticeable Difference in colour perception. How small a colour difference can you actually see?

You see two colours. Click on the line between them. That's it. It starts easy. It does not stay easy. Each round the colours get closer together until we find your Just Noticeable Difference - the smallest colour change you can actually see. It takes about 40 rounds. Most people land around 0.02. You might do better. You probably won't. But hey, prove mefrom keithcirkel.co.uk

• 
  Hex Guess2019 · hex-guess.glitch.me · ▲71

  Test your hex color guessing skills ✨

• 
  KOLOR2016 · kolor.moro.es · ▲74

  Try to guess the color as fast as possible!

• DY
  Do you know RGB?2025 · maxwellito.github.io · ▲92

  20 questions to test your RGB knowledge. How far can you go?

• AL
  A little web app for playing around with colors2019 · color.clss.hk · ▲106
• ML
  My <canvas>-based, Photoshop-esque JavaScript color picker2010 · zetamac.com · ▲73
• 
  How good is your color vision? Find out in my new game2025 · vidzert.com · ▲31

  Spot the square with a different color in this game to challenge your color perception.

• 
  SimCity, but with Permits▲930

  A free city-building game in your browser. You are the mayor. You know what the city needs. Now get it past the zoning board, the neighbors, the appeals court and the next election.

  Life & fun · 2d ago · permit.petercai.com

• IV
  I've been paying for a rural Tanzanian's education for 10 years▲778

  Life & fun · 15d ago · tanzaniaeducationproject.org

• 
  Bigwords.page – Turn any screen into a sign. The URL is the app▲728

  Turn a phone, tablet or TV into a sign. Type a message and it fills the screen: welcome signs, timers, Wi-Fi passwords and more. No app, no account, free.

  Life & fun · 16d ago · bigwords.page

• 
  Guitoro, a virtual guitar you strum with your keyboard▲573

  Play a free virtual guitar online with your keyboard or by touch. Slow songs down and see every chord, string and strum. Acoustic, classic, electric and bass.

  Life & fun · 9d ago · guitoro.com

• 
  See *almost* any carriers phone settings▲432

  Carrier settings from iPhone, Pixel and Galaxy firmware, decoded and compared: APNs, VoLTE, 5G and Wi-Fi Calling per carrier, and what each build changed.

  Life & fun · 13d ago · carrierexplode.com

• 
  The whole Solar System and every tracked satellite, live in the browser▲407

  Life & fun · 23d ago · space.bl2.net

• 
  Lightfield▲901

  AI-native CRM that builds itself and does work for you

  AI · Mar 2026 · lightfield.app

• 
  Tobira.ai▲728

  A network where AI agents find deals for their humans

  AI · Mar 2026 · tobira.ai

• 
  Claude Import Memory▲716

  Switch from ChatGPT to Claude with import memory feature

  AI · Mar 2026 · claude.com

• 
  Littlebird▲709

  Littlebird remembers everything across your meetings, messages, docs, and apps, then takes action so you can recall any detail and never lose context.

  AI · Mar 2026 · littlebird.ai

• 
  Viktor.com▲702

  Your AI Coworker that proactively executes tasks

  AI · Mar 2026 · viktor.com

• 
  Jupid▲659

  File your taxes with Claude Code

  Commerce · Mar 2026 · jupid.com