JSON Syntax Checker
Paste JSON and find out immediately whether it parses, and if not, exactly where it stops. The checker reports the line and character of the failure, highlights it in the raw view, and offers a repair for the mistakes that show up most often in hand-edited files.
Errors with a line and a character, not just "invalid"
A parse failure is only useful if it tells you where. Every error names the line and the character position where parsing stopped, and the raw view highlights that spot inline so you can see it in context rather than counting brackets down from the top.
Where the document allows it, more than one problem is reported at once, so a file with several mistakes does not turn into a fix-one-reload cycle. Duplicate keys are surfaced separately as a warning: they parse, but they nearly always mean something upstream is wrong.
The four mistakes that cause most failures
Trailing commas after the last element, single-quoted strings borrowed from JavaScript, unquoted keys, and comments are all legal in JavaScript object literals and all illegal in JSON. They account for most of what breaks a hand-edited config file, and the repair action cleans up all four without hand-editing.
The rest are usually unterminated strings, invalid escape sequences, and stray characters after the closing brace, typically from a copy that clipped the end of the document. Each one is reported with its position.
Fix it here, then keep working
Correct the JSON in raw edit mode and it revalidates as you type, so the loop is write, check, fix, with no submit button in between. Once it parses you are already in a full editor: format it, explore it in a tree, search it, or convert it to YAML, CSV, or XML.
Syntax checking versus schema validation
This page is about whether the document is well-formed JSON at all. Whether it matches a contract, meaning the required fields are present with the right types and allowed values, is a different question answered by JSON Schema validation on the validator page. Syntax checking is free and needs no account.
Frequently asked questions
Is the JSON syntax checker free?
Yes. Syntax checking, exact error positions, and the repair action are free with no sign-up. Only JSON Schema validation, which is a different kind of check, is reserved for Pro.
Why does my JSON fail when it looks fine?
The usual causes are easy to miss: a trailing comma after the last item, a single quote instead of a double quote, an unquoted key, or a comment. All four are valid JavaScript and invalid JSON.
Is my JSON sent to a server to be checked?
No. Parsing happens in your browser, so nothing is uploaded. That makes it safe for API responses and config files you would not paste into an unknown website.
What is the difference between this and the JSON validator?
This page checks that the document is well-formed JSON. The validator page adds JSON Schema validation, which checks the document against a contract of required fields, types, and allowed values.
Are very large numbers reported as errors?
No. Integers beyond the range JavaScript represents exactly, such as Snowflake IDs, are valid JSON and are preserved as written rather than flagged or rounded.