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SPECIFICTION
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jsonfmt.dev

jsonfmt.dev

Free plan WebAPI
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Spec score 7.9 #13 of 29 in JSON Tools

What it is

jsonfmt.dev is a web-based JSON formatter, beautifier and validator, with an HTTPS API for JSON processing. The formatter offers 2-space, 4-space or tab indentation, optional key sorting and depth control. It validates JSON against RFC 8259 and reports line and column errors. Other tools can repair common malformed JSON, compare two documents and convert formats including YAML, CSV, XML, TypeScript, SQL, GraphQL and Protobuf. The toolkit also includes a JWT decoder, JSON Schema validator, JSONPath evaluator and JSONL tools. The maker says the core browser tool handles JSON locally without sending its contents to the server, and continues to work offline after loading; it can also be installed as a Progressive Web App. API options include anonymous access limited to 10 requests per minute, a free API key tier with 100 requests per minute and 1,000 per month, and Pro API at $9, paid once for 1,000 requests per minute and 50,000 per month. Share links encode JSON in the URL fragment, and anyone with the link can access its contents.

Spec sheet

Product
jsonfmt.dev describes itself as a free online JSON formatter, beautifier, and validator.Read 2 Oct 2026 · jsonfmt.dev
Integrations
The maker describes an MCP server package, jsonfmt-mcp, that exposes JSON-processing tools to MCP-compatible AI clients.Read 2 Oct 2026 · jsonfmt.dev
Privacy
The maker says the core web tool processes JSON locally in the browser and does not send JSON content to its servers.Read 2 Oct 2026 · jsonfmt.dev
Support
The API pricing lists community support for anonymous access, email support for the free key tier, and priority support for Pro.Read 2 Oct 2026 · api.jsonfmt.dev
Analytics and ads
The privacy policy says the site uses Google Analytics and Google AdSense, which may use cookies; it also says local tool preferences and session data are kept in browser localStorage.Read 2 Oct 2026 · jsonfmt.dev
API access
The API accepts JSON over HTTPS and offers formatting, minifying, validation, repair, diffing, conversion, and other endpoints.Read 2 Oct 2026 · api.jsonfmt.dev
API limit
Unauthenticated API use is limited to 10 requests per minute; the documentation lists a free API-key tier at 100 requests per minute and 1,000 requests per month.Read 2 Oct 2026 · api.jsonfmt.dev
Conversion
The site lists converters for formats including YAML, CSV, XML, TypeScript, SQL, GraphQL, and Protobuf.Read 2 Oct 2026 · jsonfmt.dev
Formatting
The formatter supports 2-space, 4-space, or tab indentation, optional key sorting, and depth control.Read 2 Oct 2026 · jsonfmt.dev
Offline use
The site says it works offline after loading and can be installed as a Progressive Web App.Read 2 Oct 2026 · jsonfmt.dev
Other tools
The web toolkit also includes a JWT decoder, JSON Schema validator, JSONPath evaluator, and JSONL tools.Read 2 Oct 2026 · jsonfmt.dev
Repair and diff
Its tools can repair common malformed JSON and compare two documents, highlighting added, removed, and changed fields.Read 2 Oct 2026 · jsonfmt.dev
Share links
Share links encode JSON in the URL fragment, which the policy says is not sent in HTTP requests; anyone with the link can access its contents.Read 2 Oct 2026 · jsonfmt.dev
Validation
The site says it validates JSON against RFC 8259 and reports precise line and column errors.Read 2 Oct 2026 · jsonfmt.dev

Plans and prices

Anonymous API Free No sign-up required 10 requests/minute · all endpoints · no monthly limit · community support Read 2 Oct 2026 · api.jsonfmt.dev
Free API key Free With API key 100 requests/minute · all endpoints · 1,000 requests/month · email support Read 2 Oct 2026 · api.jsonfmt.dev
Pro API $9, paid once Pay once, Pro forever 1,000 requests/minute · all endpoints · 50,000 requests/month · priority support Read 2 Oct 2026 · api.jsonfmt.dev

Every jsonfmt.dev plan and price →

Strong points and limits

Strong points

  • Formatting includes indentation, sorting and depth controls.
  • Validation reports line and column errors.
  • The maker says browser processing stays local.
  • The toolkit includes JSON Schema and JSONPath tools.

Limits

  • Anonymous API access is limited to 10 requests per minute.
  • Free API key tier allows 1,000 requests per month.
  • Anyone with a share link can access its JSON.
  • Pro API costs $9, paid once.

Who it suits

It suits people who need browser-based JSON formatting, validation, repair or conversion, and developers who want API access. MCP-compatible AI clients can use the maker-described jsonfmt-mcp package.

Verdict

jsonfmt.dev pairs a browser toolkit with API access and several conversion and inspection tools. Consider the API limits and the access implications of share links before using those options.

Where Specifiction places it

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