Converters

YAML ↔ TOML Converter

Map YAML settings to TOML tables and TOML back to YAML. Work through nested settings, unsupported null values, and changes to comments and formatting.

Local processing

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About this tool

When to use it

Map YAML settings to TOML tables and TOML back to YAML. Work through nested settings, unsupported null values, and changes to comments and formatting.

How to use it

Use this pair when migrating named configuration settings between a YAML file and an application that reads TOML. Start with a root mapping, choose the direction, and paste the source. Convert and compare the resulting table names and values with the target application documentation. Switching direction loads a fresh example; copy any result you want to reuse first.

Guide updated 2026-09-15. Examples checked against this implementation.

Worked examples

YAML to TOML: a service table

Input

service:
  port: 3010

Expected output

[service]
port = 3_010

The nested mapping becomes a TOML table. The underscore is a TOML digit separator; the numeric value is still 3010.

TOML to YAML: restore a mapping

Input

[service]
port = 3010

Expected output

service:
  port: 3010

A table becomes an indented mapping. TOML table headings and digit separators are presentation choices and are not retained.

Errors and unsupported input

- build
- deploy

TOML needs a root table. Give the list a property name, for example tasks: [build, deploy], if that matches the target configuration schema.

service:
  token: null

TOML has no null value. Remove the field or replace it with an application-approved value. The converter rejects nested nulls instead of silently omitting them.

Continue this workflow

YAML ↔ JSON Converter: Use JSON as the target when you need explicit null values.
JSON ↔ TOML Converter: Start from an existing JSON object when YAML is not part of your workflow.

Format references

TOML parser and serializer behavior

Format rules and limitations

Input is limited to 2 MiB. YAML-to-TOML requires a mapping at the document root; arbitrary YAML documents do not have a direct TOML equivalent.

Null values are rejected anywhere in the document, including arrays. An empty string, zero, false, and an omitted key can each have different application meanings.

Comments, anchors, quote style, and original table layout are not preserved. Review parsed date/time and large numeric values before replacing a configuration file.

A successful conversion establishes that the selected serializer accepted the data; it does not prove that your application supports those keys.

Privacy and security

These tools process input in browser memory without an upload or processing API. DevMate does not save these inputs in localStorage, sessionStorage, or a share URL. Reloading starts a new workspace; browser history restoration may retain form state. Copy writes to your system clipboard and Download saves a file, which can outlive the tab. The page still loads site assets and may contact configured analytics, consent, or advertising services. DevMate analytics records route and action names, without input, output, filenames, or raw errors. Selecting Share sends the converted text to the app you choose through your device's share dialog; when native sharing is unavailable, it copies the text to the clipboard.

Review sensitive or production-critical output in the trusted system where it will be used.

Questions

Frequently asked questions

Can every YAML document become TOML?

No. Use a root mapping and values TOML can represent. Null fields must be handled explicitly and standalone lists need a named property.

Will a round trip keep the same formatting?

No. Parsed values are serialized afresh. Keep your original comments and compare important settings before replacing a file.