Minecraft guides

Practical write-ups on commands, datapacks, building and server performance — each one paired with the tool that does the work.

Commands & Data Building & Resources Server & Performance Troubleshooting

A cape texture is 2,048 pixels and only 372 of them are ever drawn

The file is 64×32, the cape lives in a 22×17 corner, and the side people actually see is 160 pixels — under 8% of the image. Plus the one-pixel offset that catches everyone.

A trimmed armour set has 1.57 billion possible appearances, which is why the lock button exists

199 states per slot to the fourth power. Rerolling all four at once will never converge on a look — locking the pieces you like turns an unsearchable space into a workable one.

A custom head stores a URL wrapped in base64 JSON, not an image

The profile component holds base64 of {textures:{SKIN:{url:…}}}. That is why a head's look is fixed at the moment it was made, and why the database can be tens of thousands of entries.

A Minecraft username is 1–16 characters of exactly three things, and a UUID has two spellings

Letters, digits, underscore. No hyphens, no dots, no spaces. And a UUID is accepted with or without its dashes — which is why one lookup fails and the identical one works.

A predicate with one condition has no wrapper, and that is a real shape change

One condition is the object itself. Two or more get wrapped in all_of or any_of. Plus the eight condition types, and why inverting is a wrapper rather than a flag.

A .nbt structure stores palette indexes, not block names — which is why it is so small

Three keys hold an entire build: size, palette and blocks. Each block is an integer pointing into the palette, so a 32³ volume of stone costs one string and 32,768 numbers.

The advancement tree: 126 advancements, and Story has no challenges at all

Adventure holds 47 of the 126 and the End just 9. 70 are dead ends, the longest chain is 8 deep, and the Story tab is the only one with zero challenge frames.

Aikar's flags change at 12 GB — five of them, and one goes down

Copying a 4 GB flag set onto a 16 GB server leaves five values wrong. Here is exactly which five, plus the player count where a modded server crosses the line and a vanilla one does not.

A Bedrock skin pack is four files, and two of its failure modes are silent

Two UUIDs that must differ, a lang file that is not optional, and skin keys that strip punctuation — so 'My Skin!' and 'My Skin?' become one skin with no error.

Bedrock has no standalone cape pack — a cape only ships attached to a skin

There is no cape-only .mcpack format. Every cape must be paired with a skin entry that names it, which is why a cape pack is really a skin pack with an extra PNG per entry.