Luau Decompiler Online

What is Luau?

Luau is the programming language Roblox games are written in. It began as a fork of Lua 5.1 and remains broadly source-compatible with it, but Roblox rewrote the compiler and the virtual machine from scratch. The result is a language that looks like Lua and adds gradual type annotations, new syntax such as compound assignment and continue, and a much faster interpreter — running on a bytecode format that shares nothing with either standard Lua or LuaJIT.

That last point is the one that matters here. Luau bytecode has no \x1b escape header at all: the very first byte of a Luau chunk is the bytecode version number. Standard Lua decompilers check for \x1bLua, find something else, and refuse the file immediately.

Three Lua Bytecode Formats, One Extension

Files from all three implementations get saved as .luac, which is the root of most of the confusion:

• Standard Lua — starts 1B 4C 75 61 (\x1bLua). Handled by the Lua decompiler.
• LuaJIT — starts 1B 4C 4A (\x1bLJ). Handled by the LuaJIT decompiler.
• Luau — starts with a bare version byte, currently in the range 1 to 6. Handled here.

You do not have to work out which you have. Upload the file and the header is read for you.

What Roblox Strips

Roblox compiles scripts server-side and ships bytecode with debug information removed. This is a deliberate protection measure and it sets a hard ceiling on what any decompiler can recover:

• Gone — local variable names, function parameter names, comments, original line numbers, and the type annotations that Luau's gradual typing allowed in the source. Type annotations are erased at compile time even in unstripped builds.
• Recovered — control flow, string constants, numeric literals, table structure, global and method names (they have to survive, because they are looked up by name at runtime), and the overall shape of every function.

In practice this means output that reads like source written by someone who names every local v1, v2, v3. The logic is intact and the API calls are legible, which is normally what you are after.

Why Luau Decompilation Is Hard

Beyond the stripping, Luau's compiler is an optimising one. It performs constant folding, dead code elimination, inlining of small functions and loop unrolling before it emits bytecode, so the instruction stream frequently has no one-to-one correspondence with anything the author wrote. A decompiler can only recover a program with equivalent behaviour, not the original text.

Luau also evolves quickly. The bytecode version has been revised repeatedly and new opcodes appear with new engine releases, so a file compiled by a recent Roblox client may use instructions that a decompiler has not been taught yet. When that happens you will get a note explaining it rather than silently wrong output.

Legitimate Uses

Decompiling bytecode you own or are authorised to analyse is ordinary engineering work: recovering your own lost source, auditing a third-party module before you take a dependency on it, investigating a malicious script that appeared in your game, or learning how a technique is implemented. Roblox's Terms of Use govern what you may do with other people's content on their platform, and this tool does not change that — it does not bypass any protection, it only reads bytecode you already have.

Frequently Asked Questions