# Compiler reference

The Motoko compiler (`moc`) is the primary tool for compiling Motoko programs into executable WebAssembly (Wasm) modules. The compiler runs in the background when you build projects using the [IC SDK](https://internetcomputer.org/docs/current/developer-docs/setup/install). If you invoke the compiler directly on the command-line, you can press CTRL-C to exit.

This section provides compiler command-line reference information.

## moc

Use the Motoko compiler (`moc`) to compile Motoko programs into executable WebAssembly (Wasm) modules.

### Basic usage

``` bash
moc [option] [file ...]
```

### Options

You can use the following options with the `moc` command.

| Option                                    | Description                                                                                                                                           |
|-------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------|
| `--actor-idl <idl-path>`                  | Specifies a path to actor IDL (Candid) files.                                                                                                         |
| `--actor-alias <alias> <principal>`       | Specifies an actor import alias.                                                                                                                      |
| `--args <file>`                           | Read additional newline separated command line arguments from `<file>`.                                                                               |
| `--args0 <file>`                          | Read additional `NUL` separated command line arguments from `<file>`.                                                                                 |
| `-c`                                      | Compile to WebAssembly.                                                                                                                               |
| `--check`                                 | Performs type checking only.                                                                                                                          |
| `--compacting-gc`                         | Use compacting GC                                                                                                                                     |
| `--copying-gc`                            | Use copying GC (default)                                                                                                                              |
| `--debug`                                 | Respects debug expressions in the source (the default).                                                                                               |
| `--error-detail <n>`                      | Set level of error message detail for syntax errors, n in \[0..3\] (default 2).                                                                       |
| `--generational-gc`                       | Use generational GC                                                                                                                                   |
| `-help`,`--help`                          | Displays usage information.                                                                                                                           |
| `--hide-warnings`                         | Hides compiler warnings.                                                                                                                              |
| `-Werror`                                 | Treat warnings as errors.                                                                                                                             |
| `--incremental-gc`                        | Use incremental GC (only for beta-testing)                                                                                                            |
| `--idl`                                   | Compile binary and emit Candid IDL specification to `.did` file.                                                                                      |
| `-i`                                      | Runs the compiler in an interactive read–eval–print loop (REPL) shell so you can evaluate program execution (implies -r).                             |
| `--map`                                   | Outputs a JavaScript source map.                                                                                                                      |
| `--max-stable-pages <n>`                  | Set maximum number of pages available for library `ExperimentStableMemory.mo` (default 65536).                                                        |
| `-no-system-api`                          | Disables system API imports.                                                                                                                          |
| `-no-timer`                               | Disables timer API imports and hides timer primitives.                                                                                                |
| `-o <file>`                               | Specifies the output file.                                                                                                                            |
| `-p <n>`                                  | Sets the print depth.                                                                                                                                 |
| `--package <package-name> <package-path>` | Specifies a `<package-name>` `<package-path>` pair, separated by a space.                                                                             |
| `--public-metadata <name>`                | Emit icp custom section `<name>` (`candid:args` or `candid:service` or `motoko:stable-types` or `motoko:compiler`) as `public` (default is `private`) |
| `--omit-metadata <name>`                  | omit icp custom section `<name>` (`candid:args` or `candid:service` or `motoko:stable-types` or `motoko:compiler`)                                    |
| `--print-deps`                            | Prints the dependencies for a given source file.                                                                                                      |
| `-r`                                      | Interprets programs.                                                                                                                                  |
| `--release`                               | Ignores debug expressions in the source.                                                                                                              |
| `--stable-types`                          | Compile binary and emit signature of stable types to `.most` file.                                                                                    |
| `--stable-compatible <pre> <post>`        | Test upgrade compatibility between stable-type signatures `<pre>` and `<post>`.                                                                       |
| `--rts-stack-pages <n>`                   | Set maximum number of pages available for runtime system stack (default 32).
| `--trap-on-call-error`                    | Trap, don't throw an `Error`, when an IC call fails due to destination queue full or freezing threshold is crossed.
|                                           | Emulates behaviour of moc versions < 0.8.0.
| `-t`                                      | Activates tracing in interpreter.
| `-v`                                      | Generates verbose output.
| `--version`                               | Displays version information.                                                                                                                         |
| `-wasi-system-api`                        | Uses the WASI system API (`wasmtime`).                                                                                                                |