YAML to TOML Converter
Convert YAML configuration to TOML 1.0, with clear stops where the formats disagree.
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How to Convert YAML to TOML
Paste a YAML configuration file and it is parsed as YAML 1.2, then re-emitted as TOML 1.0. Where a YAML construct has no TOML equivalent, the converter stops with a specific reason instead of writing something that parses but no longer means the same thing.
Where the Two Formats Differ
TOML is deliberately narrower than YAML. It has no anchors or aliases, no multi-document files, no null, and no arbitrary tags; its dates are first-class rather than strings; and its tables must be declared in a valid order. YAML permits all of the above. Converting toward TOML therefore loses expressiveness - which is often the point when you want configuration that is hard to write ambiguously.
Frequently Asked Questions
Why does my YAML file fail to convert?
Almost always because of a root that is not a mapping, or a null value. TOML requires a table at the root, so a YAML file whose top level is a list or a bare scalar has no valid TOML form. TOML also has no null type at all - remove the key or give it a real value.
Are comments carried across?
No. YAML and TOML attach comments to different structures, and there is no faithful mapping between them, so the conversion goes through the data model and comments are dropped. Both formats support comments; re-add the ones that matter after conversion.
How do nested mappings translate?
Nested YAML mappings become TOML tables written as [section] or [section.subsection] headers. A list of mappings becomes an array of tables, written as repeated [[section]] blocks.
Which TOML version is produced?
TOML 1.0, the version used by Cargo.toml, pyproject.toml, and Netlify configuration.