Introduction#

TomlSmith checks, formats, and decodes TOML 1.0 and 1.1. It is available as a Rust library, CLI, language server, and browser playground.

What you get#

In the terminal and CI:

• Validate TOML 1.0 or 1.1 and report diagnostics with source locations.
• Format documents while preserving comments and literal spellings in covered cases, or use fmt --check without changing files.
• Emit machine-readable diagnostic JSON for tools and automation.

In editors:

• Diagnostics, formatting, semantic highlighting, hover, document symbols, and folding through LSP.

In Rust applications:

• Parse a document once and query diagnostics, formatted output, highlights, and decoded values through the immutable Document API.

In the browser:

• The playground checks and formats TOML with WebAssembly in the current browser tab.

Behavior#

• TOML 1.0 and 1.1 are separate modes. Defaults differ by product surface; see the TOML version policy. Select 1.0 for files read by 1.0-only tools.
• Parse or semantic errors stop formatting. Covered formatter cases preserve comments and literal spellings.
• TomlSmith passes all 1,360 toml-test decoder cases for TOML 1.0 and 1.1. See Conformance for the scope and command.

Where to go next#

• Quick start — run the CLI against your first file.
• Use from Rust — embed the Document API.
• Editors and LSP — connect your editor.
• Performance — results and measurement method.