Check JSON as you type and get a plain verdict. When something is wrong you see the line, the column and a caret pointing at the spot, all in your browser.
Your files are processed in your browser, on your own device. Nothing is uploaded to a server.
A JSON Validator checks your JSON as you type and tells you straight away whether it is valid. When it is not, you get the error message with the line and column, plus a short snippet with a caret under the problem spot. It is free, and it runs in your browser.
There is no button to press. Paste or type JSON into the box and the verdict updates while you work. Valid JSON gets a summary line. Invalid JSON gets the error message, the position worked out as a line and column, and a snippet of the text around that position with a caret pointing at the character where parsing stopped.
The report carries the same facts you see on screen. For valid input it holds the summary numbers. For invalid input it holds the error message and the line and column, which makes it handy to attach to a bug report.
The most common scene is a failed request. You send a payload to an API, the server answers with a vague 400 error, and the real cause is a missing comma three objects deep. Pasting the payload here points at the spot in seconds, instead of reading brackets one by one in a code editor.
Config checks come a close second. A settings file that will not parse can stop an app from starting at all, and the failure message at startup rarely names the line. A validator that shows the line, the column and a caret turns a startup mystery into a one character fix, and it does it before the file reaches a server.
Hand written JSON is the third case. Fixtures for tests, seed data, webhook examples and quick mock responses all get typed by hand, and hand typed JSON drifts. A trailing comma here, a single quote there. A quick check catches the drift while the file is still open in front of you. Once the verdict is green, the JSON Formatter can tidy the same text for reading.
This tool checks syntax only. It answers one question: is this valid JSON under the standard rules. It does not check that your data matches an API contract, a set of required fields or a schema. A payload can pass here with full marks and still be rejected by an API because a field is missing or a value has the wrong type. That check needs the rules of the receiving system, and no syntax validator can know them.
The position also deserves a plain warning. The line and column show where the parser gave up, and the actual mistake often sits a character or two earlier. A missing closing quote, for example, makes the parser read on until the text stops making sense, which can be well past the real slip. Start at the caret, then look just before it.
Some legal JSON is still risky. Duplicate keys in one object are allowed, and most parsers quietly keep the last value. Very long whole numbers can lose precision when other tools parse them. Both pass a syntax check, because both are valid JSON. The verdict here means the structure is sound, not that every value will survive the trip into another system unchanged.
The check runs on your device. Your JSON is not sent to a server, not stored by ToolPeko and not read by anyone here. That matters when the payload holds tokens, customer records or internal URLs, and it is why this page works the same on private data as on a public sample. There is no account and no daily cap.
No. The check runs as you type or paste, and the verdict updates on its own. Fix a character and you see the result change right away.
A short summary: the type at the top level, such as object or array, the total number of object keys in the document, and how deep the nesting goes.
No. It shows you the error message, the line and column, and a caret under the spot where parsing stopped. The fix itself is yours to make, and the caret makes that fix quick to find.
No. This is a syntax check against the JSON standard. It cannot know which fields an API requires or which types it expects. Valid here means the JSON is well formed, not that a server will accept the data.
The position is where the parser gave up, and a missing quote or comma can let the parser travel on for a few characters before the text stops making sense. Check the caret first, then look a character or two before it.
No. Validation runs in your browser on your own device. Nothing you paste is sent to or stored on a ToolPeko server.
Same rules as this one: free, in your browser, with nothing uploaded.
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