Is my JSON uploaded anywhere?

No. Parsing, formatting and minifying are done by your browser own JSON implementation. Open the network tab and format something - no request carrying the document is made.

Why does my JSON fail here when it worked elsewhere?

Usually because the other tool tolerates comments or trailing commas. Those are not valid JSON, so a file relying on them will fail on any parser that follows the specification - which includes most of the ones in production.

Is there a size limit?

Only your browser memory. Nothing is being uploaded, so no server is imposing a cap on the paste.

Can it validate against a JSON Schema?

No. It checks syntax, not shape. For schema validation you need a validator that takes the schema as a second input.

A JSONLint alternative that does the whole round trip

JSONLint answers one question well: is this valid, and if not, where does it break. That is usually the first thing you want to know and almost never the last, because the payload you just validated still has to be read, and then usually has to go back out as a single line.

Open the JSON Formatter →

JSONLint and Softland, side by side

	JSONLint	Softland
Validation	Yes, with the position of the error	Yes, with the position of the error
Minifying back down	A separate tool	Same page, same paste
Scope	Validate and format	Validate, format and minify
Size ceiling	Whatever the page will take	Your own machine - nothing is uploaded
Advertising	Ad-supported	None

Valid is the beginning of the job, not the end of it

The reason anyone pastes JSON into a web page is that something has gone wrong. An endpoint returned a shape nobody expected, a config file will not load, a log line contains a nested object four levels deep on one unbroken line. Finding out that it parses is progress, but the actual question - which field is missing, which array came back empty, where the nesting went one level further than the code assumed - needs the document laid out.

Then it usually has to go back. Into a request body, into an environment variable, into a test fixture, into a curl command - and in every one of those places the indentation you just added is a liability. Format and minify are the same operation run in opposite directions, and splitting them across two tools means two pastes of the same sensitive document.

What actually makes JSON invalid

Nearly every failure is one of five things: a trailing comma, a key that is not double-quoted, a single quote where a double quote belongs, a comment, or NaN and Infinity appearing as numbers. JSON is stricter than the JavaScript object literal it resembles, and the gap between the two is exactly where these mistakes live.

The awkward case is a file that works in one tool and fails in another. That almost always means the permissive tool is accepting comments or trailing commas as an extension. The file is not portable JSON, whatever it looked like when it worked, and it will fail again on the next parser that follows the specification.

The payload is usually somebody else data

An API response being debugged is rarely synthetic. It has real names in it, real email addresses, real order values, sometimes an access token in a header that got copied along with the body. That is a normal thing to be holding while you work and an odd thing to post to a third party on the way to reading it.

This page reads and rewrites the document with the JSON parser already in your browser. There is no upload, so there is no retention question to ask and no size cap to run into. You can watch the network tab while you format a ten megabyte response and see that nothing goes out.

When JSONLint is the better choice

You have a bookmark and a habit, and the fastest tool is the one your fingers already know.
You want a second opinion on an error position - two parsers disagreeing about where a document breaks is itself useful information.
You need JSON Schema validation rather than syntax validation, which neither this nor a plain linter does.

Frequently asked questions

Is my JSON uploaded anywhere?: No. Parsing, formatting and minifying are done by your browser own JSON implementation. Open the network tab and format something - no request carrying the document is made.
Why does my JSON fail here when it worked elsewhere?: Usually because the other tool tolerates comments or trailing commas. Those are not valid JSON, so a file relying on them will fail on any parser that follows the specification - which includes most of the ones in production.
Is there a size limit?: Only your browser memory. Nothing is being uploaded, so no server is imposing a cap on the paste.
Can it validate against a JSON Schema?: No. It checks syntax, not shape. For schema validation you need a validator that takes the schema as a second input.

Try it yourself

Format, validate and minify JSON in your browser.

Open the JSON Formatter

JSONLint is a trademark of its respective owner. Softland is not affiliated with, endorsed by or sponsored by JSONLint. This comparison reflects how each product works rather than what either costs, because pricing and plan limits change; check JSONLint’s own site for its current terms.