MCL Skin

MCL Skin

A skin for your offline nickname, inside the game itself.

MCL Skin is the in-game half of TCLauncher. On its own it does exactly one thing: it takes a PNG that is already in the right folder, under the right name and in the right format, and shows it on your character.

Everything that gets the PNG there is TCLauncher's job: finding the skin, converting it, checking it, naming it, and installing the right mod file for your loader and game version.

Important: the mod still works without TCLauncher, but it gives you a lot less. You have to do the launcher's job yourself, by hand, every time you change your skin.

What the mod does

Vanilla Minecraft can only fetch a skin from Mojang's servers, and those servers don't know your offline nickname. Offline players are stuck as Steve or Alex. This mod fixes that, and only that.

• Reads <instance>/mclskin/skins/<nickname>.png
• Also reads <instance>/CustomSkinLoader/LocalSkin/skins/<nickname>.png, for people coming from CustomSkinLoader
• Shows that image on your character in game

One file in, one skin out.

Without TCLauncher: you create that file yourself. You find a skin, check its format, rename it to match your nickname exactly, find the instance folder, create the two folders and drop the file in. If any of those steps is wrong, you stay Steve and nothing tells you why. TCLauncher does all of it in one click.

Skin formats

• 64x64 is the modern layout
• HD skins are 128x128, 256x256 or any other multiple of 64
• 64x32 is the old pre-1.8 layout, which is still supported

The mod works out slim or classic arms from the image itself. A slim skin leaves two pixel columns of the right arm empty, and the mod checks exactly those, on both the front face and the outer side.

Without TCLauncher: the mod reads these formats but doesn't convert anything, and it only accepts PNG. A JPG, BMP, GIF or a skin with the wrong proportions won't show up, and you won't get an error. TCLauncher accepts PNG, JPG, BMP and GIF, scales them to 64x64 with nearest-neighbour (so the second layer keeps hard edges), converts 64x32 to the modern layout, works out slim or classic, and rejects images that aren't skins, telling you why.

Live reload

• The file is checked about once a second.
• The check uses the modification time together with the file size, because a copied file often keeps its original timestamp.
• Replace the PNG and the new skin appears without restarting the game.

Without TCLauncher: you swap files by hand while the game is running. TCLauncher lets you choose from a skin library and rotate a 3D preview first.

Skin transparency

New in 1.0.2.

• A slider in Options → Skin Customization.
• 0% is a normal skin, 100% is fully invisible, and anything in between is a ghost.
• The value is saved in <instance>/mclskin/settings.json.

The transparency is multiplied into the image's alpha channel before the game ever sees it. Nothing in the game's rendering is changed, so it works the same on every version and every loader.

Notes:

• The game caches a player's skin for the session, so a change made while you're in a world applies after you rejoin. If you set it from the main menu, it applies right away.
• On the old 64x32 layout, the game makes the body opaque when it converts the layout, so transparency has no effect there.
• Slim or classic is decided from the original image, never from the transparent copy.

This slider is the only thing the mod adds to the game's interface.

Startup notice

The first screen after the game starts shows a panel, in your language, explaining that the mod has far fewer features without TCLauncher.

• Close it with the Close button, Esc or Enter.
• Tick Do not show again and it won't come back (the choice is saved in settings.json).

Languages

The mod supports 15 languages, the same ones TCLauncher supports:

Ukrainian, English, Russian, Belarusian, Polish, Czech, Romanian, Spanish, French, German, Italian, Turkish, Japanese, Chinese, Filipino.

• The language follows the game's own setting from options.txt.
• If the game's language isn't on the list, or options.txt can't be read, the mod uses English.
• The setting is checked every two seconds, so switching the game's language updates the mod's text without a restart.

How the skin reaches the game

The game doesn't accept a skin as a file. It only accepts a URL, and its image loader only speaks HTTP, so a file:// path won't work. The mod works around this:

• It starts a tiny HTTP server on the loopback address 127.0.0.1, on a port the operating system picks. Nothing outside your computer can reach it.
• It serves the image under a name that is the SHA-1 hash of the image's contents. When the skin changes, the address changes too, so the game fetches the new skin instead of showing the old one from its cache.
• The game checks skin URLs against a list of allowed Mojang domains. The mod leaves that check on and adds exactly one entry: the loopback address with this session's random port.

What the mod does not do:

• No capes and no elytra. It handles skins only.
• Nothing is sent over the network. Your skin is only served to your own game, so other players on a server still see the default skin.

Compatibility

• Loaders: Fabric, Forge, NeoForge, Quilt
• Versions: Minecraft 1.14 to 26.2
• 149 files, one for each loader and version pair
• Client side only. Servers don't need it.
• Requires a mod loader. It doesn't work in pure vanilla.

The mod uses no mappings and never refers to a game method by name. Its hooks are placed by method signature instead, which is why two builds cover about forty game versions and four loaders. If a version comes along whose methods it doesn't recognise, the mod skips its interface additions and skins keep working. It won't crash the game.

Without TCLauncher: you have to pick the right file out of 149 yourself. If you pick the wrong one, it won't load and won't tell you much. TCLauncher knows each instance's loader and version and installs the matching file itself.

What TCLauncher adds

These features are part of the launcher, not the mod:

• A skin library that keeps all your skins in one place and works offline
• A full 3D model preview you can rotate with the mouse
• Take by nickname: get any licensed player's skin from Mojang's public API
• Add a skin from a file, or drag an image into the window
• Automatic conversion of PNG, JPG, BMP and GIF, including 64x32 → 64x64 and HD rescaling
• A clear error message when an image isn't a skin
• Installing the mod itself into the right instance, in the right build
• For Microsoft accounts, uploading the skin to Minecraft's own skin service so that every player on licensed servers sees it
• Removing a skin from an instance without hunting for the file

Files it creates

Path	Contents
<instance>/mclskin/skins/<nickname>.png	Your skin (placed there by TCLauncher)
<instance>/mclskin/settings.json	Transparency level and whether the startup notice was dismissed

Nothing else is written, and nothing is sent over the network.

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MCL Skin 1.0.2 is part of TCLauncher. Author: tcleo. Client side only. All rights reserved.