Free Developer Tools: JSON and Data Formats

Developer tools

Tools for the text you paste all day: the payload that will not parse, the config file that needs re-indenting, and the formats you have to hand back to a machine in exactly the shape it expects.

Data and formats

What makes a browser the right place for this

Pasting a payload into a website usually means sending it somewhere. For a JSON formatter that is a strange trade: the operation is pure text manipulation, it needs nothing from a server, and the text is often the most sensitive thing on your screen — an API response with a token in it, a config file with a connection string, a customer record you were asked to inspect.

Everything in this category runs in the page you already loaded. There is no upload, no request to our server and no logging, because there is nothing to send: the page imports one small module of pure functions and works from there. It also means no usage limit, since a calculation that stays inside your browser costs us nothing to run.

A formatter that repairs your JSON is not helping you

The most common feature in this category is the one we refused to build: silently fixing what you paste. Deleting a trailing comma, converting single quotes, stripping comments — all of it produces a file that looks correct in your editor and still fails in the program you send it to. Worse, it hides the only fact worth knowing, which is usually that the text was never JSON to begin with.

The tools here report the line, the column and a plain-language reason, and they stop there. The decision about what the data was meant to be is yours, and so is the fix. Two specific cases get called out because they change your data even when the JSON is perfectly valid: duplicate keys (every JavaScript engine keeps the last one) and integers beyond 2⁵³ − 1 (a 20-digit ID is already rounded by the time anything can read it).

What belongs in this category next

The plan for developer tools is short and deliberately unglamorous: the conversions that come up while debugging, each of which can be done with browser-native APIs and no data of any kind.

• Encoding and decoding — Base64 and URL encoding, including the Unicode cases where the naive approach produces mojibake rather than an error.
• Hashes — SHA-256 and friends through the Web Crypto API, for checking that a file arrived intact.
• Timestamps — Unix time to a readable date and back, with the time-zone handling done through the browser's own time-zone data rather than a table we maintain.

Each one ships in English and Chinese before it is listed here, which is why this page lists one tool rather than five. A link to something that does not exist yet is not a roadmap, it is a broken promise.

Which one do you need?

• A payload that will not parse, and you need to know where? Use the JSON formatter and validator: it gives the line, the column and a plain-language reason, and it also reports duplicate keys and integers too large to hold exactly.
• JSON that parses but is unreadable on one line? Same tool — choose 2 spaces, 4 spaces or a tab and press Format. Minify does the reverse when you need to paste it back into a request body.
• Text that needs counting rather than parsing? Use the word and character counter, which handles Chinese and Japanese by character instead of by whitespace.

Other tools and guides on this site

Developer tools are the third category on this site; the other two answer different questions.

• All tools — every calculator and utility, grouped by what it is for.
• Everyday tools — dates, working days, word counts and percentages.
• Career tools — notice periods, offer comparison, equity vesting and the ATS keyword check.
• Editorial policy — how these pages are written and what we refuse to state without a citable source.

Common questions

Does my JSON get uploaded to your server?

No. The formatter imports one small module of pure functions and does everything in the page you already loaded: parsing, formatting, minifying and the download. There is no request to our server, nothing is logged, and closing the tab discards the text you pasted.

Why is there only one tool in this category so far?

Because the page is honest about what exists. Encoding, hashing and timestamp tools are planned for it, and each one ships in both English and Chinese before it is listed — an empty hub or a stub that returns nothing would be a worse answer than a short list. A category page is only created once it has a real tool in it, which is why this one appeared together with the JSON formatter rather than before it.

Will these tools fix my JSON for me?

No, deliberately. A formatter that deletes a trailing comma or converts single quotes makes a file look correct here and still fail wherever you send it next, while hiding the real problem. The tool reports the line, the column and a plain-language reason, and leaves the decision about what the data was meant to be to you.

Do the tools work offline?

Yes. Once the page has loaded, the module is local and no network call is involved, so a lost connection changes nothing. Parsing itself needs JavaScript — the page says so and explains the rules instead of leaving you with a button that does nothing.

I have API keys and tokens inside my JSON. Is that a problem?

Nothing is transmitted from the page, so the tool cannot leak them. That does not make pasting live credentials a good habit: the clipboard, the downloaded file and browser memory are all outside this page, and a shared or managed machine is a bigger risk than any website. The tool shows you what it saw; what you carry around is still your call.