About JSON Validator & Formatter
A fast, free JSON formatter, validator and editor that treats your data the way it should be treated: it never sees it.
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Your JSON stays in your browser
Most online JSON tools send your document to a server to format or validate it. JSON Validator & Formatter doesn't have a server to send anything to. The entire application is static files, and every feature (parsing, validation, formatting, diffing, conversion) runs as JavaScript in your browser. Your JSON is never uploaded, logged or stored anywhere but your own device. That makes it safe for API payloads, configuration files and anything else you'd rather not paste into a stranger's server.
The website itself uses a small amount of standard analytics and advertising (described in the privacy policy below), but those never receive the contents of the JSON you edit. The document you paste stays local.
What it does
- Validate against RFC 8259, RFC 7159, RFC 4627 or ECMA-404, with line-precise, human-readable error messages and in-text highlighting.
- Auto-fix common mistakes in one click: trailing commas, single quotes, unquoted keys, comments, missing brackets.
- Edit visually in a tree or table view: click any key or value to change it, toggle booleans, pick colors, add or delete entries. Or edit raw text with syntax highlighting.
- Compare two documents side-by-side with a line diff.
- Convert & export to formatted JSON, minified JSON, YAML, CSV or plain text.
- Preserve big numbers with a lossless parser, so 64-bit IDs survive editing without silent precision loss.
- Share a document as a link, work in dark or light mode, and undo anything.
Free to use
There is no account to create, no paywall and no usage limit. The tool is free for everyone, and it stays free because it is supported by unobtrusive display ads. Those ads help cover the cost of running the site; they never receive the JSON you work with, which is processed entirely on your own device.
How it's built
JSON Validator & Formatter is a single-page application built with React and Vite. The JSON tokenizer, linter, lossless parser, formatter and diff engine are all custom, dependency-free implementations, so the production bundle stays small and loads fast. Your documents and settings persist locally via your browser's storage, never remotely.
Privacy Policy
Last updated: July 14, 2026
This privacy policy explains what information JSON Validator & Formatter (“we”, “us”), available at perfectjson.com, collects and how it is used. In short: the JSON documents you edit stay on your device, and the only data we handle is the standard, anonymous usage data described below.
The JSON you edit
The content you paste, type, open or generate in the editor is processed entirely in your browser. It is never transmitted to us or to any third party. Your documents and preferences are saved only in your browser's local storage on your own device, and you can clear them at any time from the app or your browser settings.
Analytics
We use Google Analytics to understand aggregate usage, such as which pages are visited and roughly how many people use the tool. Google Analytics sets cookies and collects standard information like your browser type, referring page and an approximate, IP-derived location. This data is aggregated and is not used to identify you personally. You can learn more from Google's privacy policy, and you can opt out with the Google Analytics opt-out browser add-on.
Advertising and cookies
- We use Google AdSense to display ads. Third-party vendors, including Google, use cookies to serve ads based on your prior visits to this and other websites.
- Google's use of advertising cookies enables it and its partners to serve ads to you based on your visit to this and/or other sites on the internet.
- You may opt out of personalized advertising by visiting Google Ads Settings. You can also opt out of a third-party vendor's use of cookies for personalized advertising at aboutads.info.
- If you are in the European Economic Area, the United Kingdom or Switzerland, we show a consent message through a Google-certified Consent Management Platform, and ads are served according to the choice you make there.
What we do not do
We do not sell your personal information, we do not require an account, and we never receive the contents of your JSON documents.
Third-party links
Some pages link to external sites (for example the specifications and tools referenced in the guide). We are not responsible for the privacy practices or content of those sites.
Changes to this policy
We may update this policy from time to time. Material changes will be reflected here with a new “last updated” date. Questions? See Contact below.
Terms of Use
Last updated: July 14, 2026
By using JSON Validator & Formatter you agree to the following terms.
- Free service, provided “as is”. The tool is provided free of charge, without warranties of any kind, express or implied, including fitness for a particular purpose. We do not guarantee it will be uninterrupted, error-free, or that any operation (validation, auto-fix, conversion) is correct for every input.
- Your data is your responsibility. Because everything runs in your browser, you are responsible for keeping your own copies of anything important. We are not liable for any loss of, or changes to, your data.
- Limitation of liability. To the maximum extent permitted by law, we are not liable for any direct, indirect, incidental or consequential damages arising from your use of, or inability to use, the tool.
- Acceptable use. Do not attempt to disrupt the service, abuse it in a way that harms other users, or use it for any unlawful purpose.
- Changes. We may update the tool and these terms at any time. Continued use after changes constitutes acceptance of the updated terms.
Contact
Spotted a bug, want a feature, or have a question about privacy or these terms? We'd like to hear from you.
- Feedback, bugs & feature requests: [email protected]
- Security & privacy: [email protected]
The changelog shows how much of this tool exists because someone asked for it.