JSON Validator and Formatter

A JSON validator and formatter checks JSON online for syntax errors and reformats it for readability. Validation reports exact line and column details that point to the problem, rather than a generic parse failure. Pretty printing applies consistent two-space indentation, while compressing minifies the output for faster transfer and storage. The workflow supports API debugging, configuration file hygiene, and data review.

Validating JSON checks whether text parses as strict JSON and, if not, reports exactly where it fails; formatting then presents the result either pretty-printed with two-space indentation for readability or compressed to a single line for faster transfer and storage.

Parsing JSON that fails to validate produces an error panel giving the exact line and column of the problem, with a caret marking the position, rather than a generic parse-failure message. Live validation can check the input continuously while typing, with an adjustable debounce interval to balance responsiveness against performance on very large documents.

An Allow Comments mode accepts JSONC syntax, single-line (//) and multi-line (/* */) comments, during validation, so an annotated configuration file carrying comments that strict JSON forbids still validates correctly.

The validated result can be copied to the clipboard or downloaded as a .json file, in either its pretty-printed or compressed form.

The validator and formatter apply to common development and data tasks:

• Validate API requests and responses to ensure correct quoting, commas, escapes, numeric formats, and valid literals such as true, false, and null.
• Clean configuration files such as package.json, tsconfig.json, and app settings to improve readability and consistency.
• Pretty print complex objects during code review to reduce confusion and speed up debugging.
• Minify large payloads before logging or transport to reduce size without changing data.
• Normalize output before commits to reduce diff noise and keep stable formatting across teams.

A small object demonstrates formatting and validation: {"user": {"id": 42, "name": "Ada"}, "roles": ["admin", "editor"], "active": true, "meta": null}.

The same object with a trailing comma, {"user": {"id": 42, "name": "Ada",}}, demonstrates line and column error reporting: the parser flags the position of the comma that precedes the closing brace.

Removing the trailing comma restores valid JSON. From there the same object can be compressed to a single line or pretty-printed with two-space indentation.

A success banner confirms that the JSON is valid. When it is not, the error panel gives the exact line and column of the syntax problem, with a caret marking the position. Common mistakes include trailing commas, single quotes in place of double quotes, unescaped characters inside strings, and malformed numbers. Pretty printing reveals structure; compressing minimizes size when preparing data for logs or transport.

Does this support comments? Yes. JSONC mode accepts // and /* */ comments during validation, which is useful when validating annotated configuration files.

What is the difference between pretty print and compress? Pretty print formats JSON with two-space indentation for readability. Compress removes extra whitespace to create a compact single-line string for network transfer or storage.

How are results shared? The JSON can be copied to the clipboard or downloaded as a .json file for attaching to a message or committing to a repository.

Why does an error appear when an API accepts the same payload? Some systems accept loose JSON, but strict JSON requires double-quoted strings, no trailing commas, valid escapes, and proper numeric formats. Strict validation surfaces exactly which of those rules a payload violates, even when a permissive API parser accepts it anyway.