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JSON validation checks whether a string conforms to the JSON specification (ECMA-404 / RFC 8259). A valid JSON document must use double-quoted strings for keys and string values, separate items with commas (no trailing commas), use correct bracket pairing for objects ({}) and arrays ([]), and contain only permitted value types: string, number, boolean, null, object, or array. Even a single misplaced character — a missing comma, an extra bracket, or a single-quoted string — makes the entire document invalid and causes parse failures in every language and framework.
Paste your JSON into the editor on this page. The validator runs instantly in your browser, parsing the input and checking every token against the JSON specification. If the JSON is valid, you see a green confirmation with the formatted output. If there is an error, the validator highlights the exact line and character position where the problem occurs and describes the issue in plain English — for example, 'Expected comma or closing brace at line 15, column 3'. This pinpointed feedback makes fixing errors fast, especially in large documents where the problem would be nearly impossible to spot by eye.
The most frequent JSON errors developers encounter are: trailing commas after the last item in an object or array (allowed in JavaScript but not in JSON), single-quoted strings instead of double quotes, unquoted keys, comments (// or /* */), undefined or NaN values, and hexadecimal number literals (0xFF). Each of these is valid in JavaScript but violates the JSON specification. Another common mistake is copying JSON from a formatted log that includes extra characters like line numbers or timestamps — always strip non-JSON content before validating. If you frequently work with relaxed JSON formats, consider writing the data as standard JSON from the start to avoid repeated validation failures.
Integrating JSON validation into your workflow prevents bugs before they reach production. Validate API request and response payloads during development. Add JSON schema validation to your CI/CD pipeline for configuration files. Use pre-commit hooks to check JSON syntax in committed files. For quick ad-hoc checks — inspecting a webhook payload, testing a cURL response, or verifying a manually edited config — this online validator gives you instant feedback without installing any tools. All processing runs locally, so it is safe to validate sensitive data like API keys and tokens.