Is It Safe to Paste JSON Into an Online Tool?
Is it safe to paste JSON into an online tool? Only if it never sends your payload anywhere. These do not, and you can verify that yourself.
Is it safe to paste JSON into an online tool? It depends entirely on one thing: whether that tool sends your payload anywhere. Most do, because parsing on a server is the easy way to build them. These do not. Everything here runs as JavaScript in the page you have already loaded, which is the only reason it is reasonable to paste a JWT or a production API response into a web page at all.
Do not take that on trust, from this site or any other. Open your browser's network tab, paste something in, and watch whether a request goes out carrying it. That check takes ten seconds and it is the only claim about privacy worth anything. Nothing here is logged, stored or transmitted, and closing the tab is enough to be rid of it.
Small differences between these tools matter more than people expect. I ran the three JSON formatters most developers already have installed, expecting the same output, and got three different answers: python -m json.tool indents with four spaces, jq indents with two, and given the same malformed input they exit with codes 1 and 5. If a CI script checks for a specific exit code, that decides whether your build fails. The article on formatting JSON goes through it properly.
The other reason to prefer a local tool is that error messages from a browser parser are usually better than the one your language gave you. A JSON parse failure reported at position 34 is not where the mistake is; it is where the parser finally ran out of patience. A missing closing brace on line 2 gets reported at the end of the file, because that is the first point the document becomes impossible rather than merely incomplete. Knowing to read upward from the reported line saves more time than any amount of squinting at the line itself.
The JSON Formatter is live. Base64 encoding and decoding, a JWT decoder and a UUID generator are planned.
Developer Tools
JSON Validator, JSON Minifier, Base64 Encoder, Base64 Decoder, UUID Generator and JWT Decoder are in development.
Guides and explanations
Longer pieces that go past what a tool page can show you.
Frequently asked questions
Is it safe to paste a JWT or an API payload into this site?
Safer than into most, because nothing is transmitted. These tools are client-side JavaScript: your input is parsed by your own browser, and there is no request carrying it to a server, no log line and no database row. You can confirm this yourself by opening your browser's network tab while using any tool on this site and watching that no request is made.
Do I need an account?
No. There are no accounts on this site at all, for any tool. Nothing is saved between visits, which also means nothing can be leaked or subpoenaed later.
Why use a web tool instead of jq or a code editor?
Usually you should use the local tool, and the article on formatting JSON says so plainly. A web tool wins in three situations: you are on a machine that is not yours, you want a readable error message pointing at the exact character that broke the parse, or you are checking one payload and installing something would take longer than the task.
Do these work offline?
Not fully. The processing happens on your device, but the page itself still has to be downloaded, so the first load needs a connection. There is no service worker caching the site for offline use yet. Once a page is loaded, using it does not require the network.