Minecraft tools
Various tools to help you play Minecraft. Like everything else here, they run entirely in your browser. Nothing to install, just select the one you need right now.
Coordinates/navigation
Nether portal calculatorOverworld to Nether coordinates converter, and vice versa. Especially useful when you're trying to build linked portals.
Stronghold finder (end portal)Throw two eyes of ender, write where they flew, get the stronghold's coords. No seed needed.
Seed finders
Slime chunk finderAll the slime chunks of your world on a grid, with a list of the best spots to AFK at, so you can activate as many slime chunks as possible around you.
Building
Circle and sphere generatorPixel circles, ovals, spheres and domes, block by block and layer by layer, with the number of blocks you need.