jsonfmt.dev

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What jsonfmt.dev is

jsonfmt.dev is an online JSON formatter, validator, and set of related tools, available in a browser and through an HTTPS API. Its formatter offers 2-space, 4-space, or tab indentation, optional key sorting, and depth control. It checks JSON against RFC 8259 and reports line and column errors; additional tools repair common malformed JSON, compare documents, and convert formats including YAML, CSV, XML, TypeScript, SQL, GraphQL, and Protobuf. The web toolkit also includes JSON Schema validation, JSONPath evaluation, JWT decoding, and JSONL tools. The maker says the core web tool handles JSON locally in the browser, works offline after loading, and can be installed as a Progressive Web App. The API supports formatting, minifying, validation, repair, diffing, conversion, and other endpoints. Anonymous API access allows 10 requests per minute; a free API key allows 100 per minute and 1,000 per month. Pro API costs $9, paid once and allows 1,000 per minute and 50,000 per month. Share links encode JSON in the URL fragment, accessible to anyone with the link.

Who it suits

jsonfmt.dev suits people who need browser-based JSON formatting, validation, repair, conversion, or comparison tools. Its API tiers also serve developers who need to process JSON programmatically.

What it does well

Formatting offers indentation, key sorting, and depth controls
Reports JSON errors by line and column
Includes repair, comparison, conversion, and schema tools
Core browser tool can work offline after loading
Free API key allows 1,000 requests per month

What to know first

Anonymous API access is limited to 10 requests per minute
Anyone with a share link can access its JSON
Pro API costs $9, paid once

Limits

Anonymous API access allows 10 requests per minute. The free API key tier allows 100 requests per minute and 1,000 requests per month; Pro API costs $9.00 USD once and allows 1,000 requests per minute and 50,000 requests per month.

Plans

Plan	Billed and limits	Price
Free API key	With API key · 100 requests/minute · all endpoints · 1,000 requests/month · email support	Free
Anonymous API	No sign-up required · 10 requests/minute · all endpoints · no monthly limit · community support	Free
Pro API	Pay once, Pro forever · 1,000 requests/minute · all endpoints · 50,000 requests/month · priority support	$9, paid once

As jsonfmt.dev lists them, read 2 Oct 2026. The maker's own page has the final word.

Getting started

Open https://jsonfmt.dev/ in a web browser.
Use the browser tools for formatting, validation, repair, comparison, or conversion.
Install it as a Progressive Web App if you want an installed version.
For API use, send JSON over HTTPS; use anonymous access or obtain a free API key.
For compatible AI clients, use the jsonfmt-mcp package.

Verdict

jsonfmt.dev combines browser tools with an API for common JSON tasks, plus converters and related utilities. Check the API request limits and remember that shared-link contents are accessible to anyone who has the link.

Questions

Is jsonfmt.dev free?

The browser tool describes itself as free. API access includes a free anonymous option and a free API key tier.

What does the free API access include?

Anonymous access requires no sign-up and allows 10 requests per minute with no monthly limit. A free API key allows 100 requests per minute and 1,000 requests per month.

How much does Pro API cost?

Pro API costs $9.00 USD once, with 1,000 requests per minute and 50,000 requests per month.

Which platforms are available?

The listed platforms are web, API, and Chrome extension.

Does jsonfmt.dev support JSON Schema and JSONPath?

Yes. Schema validation and JSONPath querying are listed as supported.

Does the browser tool send JSON to its servers?

The maker says its core web tool processes JSON locally in the browser and does not send JSON content to its servers.

Facts from jsonfmt.dev's own pages

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. · jsonfmt.dev, 2 Oct 2026
API access: The API accepts JSON over HTTPS and offers formatting, minifying, validation, repair, diffing, conversion, and other endpoints. · api.jsonfmt.dev, 2 Oct 2026
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. · api.jsonfmt.dev, 2 Oct 2026
Conversion: The site lists converters for formats including YAML, CSV, XML, TypeScript, SQL, GraphQL, and Protobuf. · jsonfmt.dev, 2 Oct 2026
Formatting: The formatter supports 2-space, 4-space, or tab indentation, optional key sorting, and depth control. · jsonfmt.dev, 2 Oct 2026
Integrations: The maker describes an MCP server package, jsonfmt-mcp, that exposes JSON-processing tools to MCP-compatible AI clients. · jsonfmt.dev, 2 Oct 2026
Offline use: The site says it works offline after loading and can be installed as a Progressive Web App. · jsonfmt.dev, 2 Oct 2026
Other tools: The web toolkit also includes a JWT decoder, JSON Schema validator, JSONPath evaluator, and JSONL tools. · jsonfmt.dev, 2 Oct 2026
Privacy: The maker says the core web tool processes JSON locally in the browser and does not send JSON content to its servers. · jsonfmt.dev, 2 Oct 2026
Product: jsonfmt.dev describes itself as a free online JSON formatter, beautifier, and validator. · jsonfmt.dev, 2 Oct 2026
Repair and diff: Its tools can repair common malformed JSON and compare two documents, highlighting added, removed, and changed fields. · jsonfmt.dev, 2 Oct 2026
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. · jsonfmt.dev, 2 Oct 2026
Support: The API pricing lists community support for anonymous access, email support for the free key tier, and priority support for Pro. · api.jsonfmt.dev, 2 Oct 2026
Validation: The site says it validates JSON against RFC 8259 and reports precise line and column errors. · jsonfmt.dev, 2 Oct 2026

Where jsonfmt.dev stands on Freedom251

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