What you can do here
Build round things without guessing. Minecraft is made of cubes, so circles, towers, arenas and domes are hard to get right by eye. The circle generator shows every block of a circle or oval of any size, and the sphere & dome generator splits a sphere into layers you can build one at a time.
Travel faster through the Nether. One block in the Nether equals eight blocks in the Overworld. The Nether portal calculator tells you exactly where to build the matching portal so the two link correctly.
Brew the right potion. The potion chart lists every brewable potion with its ingredient, effect and duration, and the brewing chart walks through the brewing stand from water bottle to splash and lingering potions.
Make your server and videos look good. Create blocky pixel-style titles with the font generator, colorful chat and MOTD text with the gradient generator, and custom flags with the banner maker.
Which version do the tools follow?
Geometry tools work in every version, because they only depend on blocks. Game data such as potion durations and banner patterns follows the current Java Edition. Where Bedrock Edition behaves differently, the page says so.