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mops build

Build Motoko canisters defined in mops.toml

mops build

Compiles Motoko canisters to WebAssembly (Wasm) modules and generates Candid interface files.

Canisters must be defined in the [canisters] section of your mops.toml file.

The build command will automatically:

  • Add Candid metadata to the Wasm modules
  • Validate Candid compatibility (if a candid file is specified in canister config)

Examples​

Build all canisters defined in mops.toml

mops build

Build specific canisters

mops build backend frontend

Build with verbose output

mops build --verbose

Build with custom output directory

mops build --output ./build

Pass additional arguments to the Motoko compiler

mops build -- --release --ai-errors

Options​

--verbose​

Show detailed build information including compiler commands and build times.

--output, -o​

Specify the output directory for compiled Wasm and Candid files.

Default .mops/.build

mops build --output ./dist

Configuration​

Canisters are defined in your mops.toml file:

[canisters.backend]
main = "src/main.mo"
args = []

Each canister configuration supports:

  • main - Path to the main Motoko file (required)
  • args - Additional compiler arguments for this specific canister (optional)
  • initArg - Candid-encoded initialization arguments (optional)
  • candid - Path to the Candid interface file (optional, for compatibility checking)

You can also set global build arguments:

[build]
args = ["--release", "--ai-errors"]

Candid Compatibility​

If a candid field is specified in the canister configuration, the build command will automatically check that the generated Candid interface is compatible with the specified interface.

If the compatibility check fails, the build will fail with an error message.

For manual compatibility checking, see mops check-candid.