Pick JSON → TOML or TOML → JSON
Tabs switch labels, placeholders, and which file types the uploader suggests.
JSON ↔ TOML Converter
Switch between JSON and TOML for Cargo, pyproject, and other configs. Pick a direction, paste or upload, then copy or download. Uses @iarna/toml (ISC) bundled on this page—nothing is sent to a server. For YAML, use JSON ↔ YAML; for JSON-only formatting, use the JSON formatter.
Or upload a JSON file
Max 10 MB UTF-8 · processed locally
Output
Output
Runs only in your browser. Bundled @iarna/toml (ISC).
HOW IT WORKS
How to convert JSON and TOML online
Choose a direction, validate input with Convert, then copy or download the other format.
Paste or upload
Stay under the size limit. JSON must be valid; for TOML output the JSON root must be a single object (not an array).
Convert and export
For TOML → JSON, choose indent, then copy or download .json or .toml.
Why use this tool
Why Use a JSON ↔ TOML Converter?
Rust (Cargo.toml), Python (pyproject.toml), and many static-site configs use TOML, while APIs and browsers favor JSON. Converting locally keeps tokens and secrets off third-party paste sites.
Config workflows
Turn JSON samples into TOML snippets for manifests—or flatten TOML to JSON for tools that only accept JSON.
No CLI required
Paste from docs or CI logs without installing taplo or other CLIs.
Explicit errors
Invalid JSON or TOML surfaces the parser message so you can fix syntax quickly.
Pretty-printed JSON
TOML → JSON supports 2- or 4-space indentation for readable output.
Privacy
Private and Secure
Conversion runs entirely in your browser. Text and files are not uploaded, logged, or stored on any server.
Local processing
@iarna/toml runs in your tab only; your data never leaves the device.
No account or API
No keys, quotas, or backend—just static pages and scripts.
Size limits on purpose
Large pastes are rejected to reduce memory pressure and keep the tab responsive.
FAQ
Frequently asked questions
About 10 MB of UTF-8 text per paste or file, aligned with other JSON tools on this site.
A TOML document is a set of key/value pairs at the root (a table), not a bare array. Wrap arrays in an object key if you need to represent them.
JSON has no native datetime. Parsed TOML dates become ISO strings in JSON; converting back to TOML may use a different but equivalent representation.
No. Parsing and stringifying run in your browser; the library ships with the page.
The formatter only prettifies or minifies JSON. Here you change the serialization format between JSON and TOML.