jsonfmt.dev review
A broad JSON toolkit with local browser processing, API access, and a $9 one-time Pro plan.
Reviewed by iTechGuides Editors · Editorial team · Updated Oct 2026
jsonfmt.dev is a browser-based JSON toolkit for developers who need more than formatting and minification. Its feature set includes configurable indentation, RFC 8259 syntax validation, JSON Schema validation with detailed errors, JSONPath queries, side-by-side diffing, format conversion, malformed JSON repair, JSONL processing, and JWT inspection. The web application processes data locally in the browser and works offline after loading, while the REST API supports scripts, CI/CD pipelines, testing, and automation. It is best suited to developers and power users handling varied JSON workflows rather than occasional users seeking only a basic formatter.
The published plans provide three access levels. Anonymous access costs $0 and includes all endpoints, with 10 requests per minute, no monthly limit, and community support. The Free plan also costs $0 and raises the limit to 100 requests per minute while retaining all endpoints and adding email support. Pro costs $9 as a one-time payment and includes all endpoints, 1,000 requests per minute, priority support, and “Pay once, Pro forever.” This structure makes the free options practical for lighter work, while Pro is aimed at recurring API or automation use where request volume and support response matter.
jsonfmt.dev also fits workflows beyond its web interface through its REST API, CLI tool, MCP server, and Chrome browser extension. JSONL parsing, validation, and conversion add useful coverage for line-delimited data, and JSONPath supports filters, recursive descent, and slices. The trade-off is focus: jq querying is not included, so teams built around jq-specific expressions may prefer a tool centered on that workflow. Choose jsonfmt.dev for broad JSON inspection, repair, conversion, and API access in one product; choose an alternative if jq compatibility is a core requirement or if only minimal formatting is needed.
jsonfmt.dev pros and cons
- Where it wins
- Covers formatting, validation, JSONPath, diffing, repair, and conversions
- Processes JSONL and offers JWT decoding and inspection
- REST API, CLI, MCP server, and Chrome extension support
- Where it doesn't
- No jq querying
- Pro rate limit is needed for higher request volume
- The toolset may exceed the needs of basic formatting tasks
jsonfmt.dev fact sheet, pricing and score →
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