Validate, analyze, format, and lint your JSON data strings in real-time.
What this validator checks, why syntax errors break server-side code before you ever see them, and answers to the questions we get asked most.
JSON has no tolerance for small mistakes — a missing comma, an extra bracket, or a single unquoted key makes the entire payload unparseable, and most languages will throw a hard error rather than guess at what you meant. Checking the syntax before you send that data to a server, save it to a config file, or commit it to a repository catches the mistake while it's still a one-line fix, instead of after it's caused a failed API call or a broken deploy.
A JSON validator is a tool that checks whether a piece of text follows the JSON specification exactly — and if it doesn't, tells you where it fails rather than just saying "invalid."
The rules are strict and specific: every key and every string value needs double quotes (not single quotes), objects and arrays need matching opening and closing braces or brackets, entries need commas between them but never after the last one, and numbers can't have leading zeros or trailing decimal points. A validator applies these rules the same way a program's JSON parser would, so if your file passes here, it will load correctly in your application too.
When a request payload, config file, or API response contains invalid JSON, the code that's supposed to read it usually fails immediately and stops the process it's part of — a form submission, a build step, a background job — often with an error message that doesn't say which part of the file is wrong.
Pasting the same data into a validator gives you the specific line and column of the problem instead of a generic parse failure, so you're fixing the actual broken comma or brace rather than reading through the whole file by eye. This is especially useful for JSON generated by another system — a script, an export, an API you don't control — where the error could be anywhere in a large file.
Errors are reported with the exact line and column, not just a generic "invalid JSON" message.
Validation follows the JSON specification exactly, so anything that passes here will parse in your application too.
Parsing and validation happen entirely in your browser — nothing you paste is ever sent to a server.