About Stellardle

Stellardle is a free daily puzzle game for astronomy enthusiasts. Each day, a mystery constellation is chosen from the 88 officially recognized IAU constellations. Your goal is to identify it in as few guesses as possible using a set of spatial clues.

How to Play

1. Type the name of any constellation into the guess field and submit.
2. After each guess you receive feedback use either game mode:
   • Angular distance/Directional bearing — how far your guess is from the mystery constellation on the celestial sphere, in degrees and the compass direction from your guess toward the mystery constellation (N, NE, E, SE, S, SW, W, NW).
   • Declination/Right Ascension — the difference Dec and RA of your guess compared to the mystery constellation, in degrees and hours respectively. This is like latitude and longitude on the celestial sphere.
3. Use the clues to zero in on the mystery constellation with each guess.
4. You have up to 6 guesses. Find it in fewer for a better score!

Game Modes

• Daily mode — One new constellation puzzle every day, shared by all players worldwide. Come back tomorrow for the next one.
• Practice mode — A randomly selected constellation each time. Play as many rounds as you like to sharpen your knowledge of the night sky. Filter by hemisphere if you want.

The Constellation Pool

Stellardle draws from all 88 constellations recognized by the International Astronomical Union (IAU), spanning both the northern and southern hemispheres — from Andromeda and Orion to Crux and Centaurus.

Tips

• Start with constellations near the celestial equator to cover the middle of the sky and get useful directional feedback quickly.
• Pay attention to bearing: if the arrow points north-east, the answer is north and east of your guess.

Built for Fun

Stellardle was built as a passion project for anyone who loves the night sky. It is free to play, with no accounts or sign-ups required.