YAML to TOML Converter

Transform YAML documents to TOML configuration format with proper table structure and types.

YAML to TOML Converter tool

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Example

Input: title: App / server: / port: 8080 (port indented under server)

Result: title = "App" / (blank line) / [server] / port = 8080

The nested server mapping becomes a [server] table and the string App is quoted as TOML requires.

  1. Paste your YAML document into the input area on the left side.
  2. The tool validates the YAML syntax and reports any indentation or parsing errors.
  3. Review the generated TOML output with proper [table.headers] and key-value formatting in the right panel.
  4. Verify that YAML sequences are correctly converted to TOML inline arrays or [[arrays of tables]].
  5. Click the copy button to copy the TOML configuration for use in your Rust or Python project.

Converting YAML to TOML Step by Step

This tool turns a YAML document into TOML. Top-level values become key = value lines, nested mappings become [table] sections, and lists of mappings become [[array]] tables. So title: App with a nested server: port: 8080 becomes title = "App", then [server] and port = 8080.

TOML is stricter than YAML, so a few things change. The top level must be a mapping; a list or a single value at the root shows an error. TOML has no null, so keys set to ~, null or left empty are dropped, and a list that contains a null cannot be converted at all. Plain values are written before any [table] section, because in TOML every key after a header belongs to that table.

This direction reads YAML with the full default schema, which has two effects. A bare date such as 2024-01-15 is read as a timestamp and written as the TOML date-time 2024-01-15T00:00:00.000Z. Put it in quotes in the YAML if you want to keep it as text. Anchors, aliases and << merge keys are all resolved, so shared blocks are copied into each place they are used. Comments are dropped.

Only a single document is allowed, so split files that use --- first. The panels also convert TOML back to YAML. If your data starts as JSON, use the JSON to TOML Converter instead.

Sources

Frequently Asked Questions

TOML has no null type, so keys whose YAML value is ~, null or empty are left out of the TOML. If your program needs the key, give it a real value such as an empty string or false. A list that contains a null cannot be written and shows an error.
This converter reads YAML with the default schema, where an unquoted 2024-01-15 is a date. It becomes a JavaScript date at midnight UTC and is written to TOML as 2024-01-15T00:00:00.000Z. Quote the value in the YAML, as "2024-01-15", to keep it as a plain string.
A list of plain values becomes an inline TOML array, such as ports = [ 80, 443 ]. A list of mappings becomes an array of tables, with one [[name]] header per item. Mixed lists become inline arrays too, with any mappings written as inline tables.

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