# rustfmt > Tool for formatting Rust source code. > More information: . - Format a file, overwriting the original file in-place: `rustfmt {{source.rs}}` - Check a file for formatting and display any changes on the console: `rustfmt --check {{source.rs}}` - Backup any modified files before formatting (the original file is renamed with a `.bk` extension): `rustfmt --backup {{source.rs}}`