JSON Fixer: Repair Invalid JSON Instantly

How to use the json fixer

1. Paste your broken or invalid JSON into the text area.
2. The json fixer automatically scans for common syntax errors as you type.
3. Review the repaired JSON in the output box.
4. Check the list of fixes applied below the output to understand what changed.
5. Copy the valid JSON for use in your application or API.

What this json fixer repairs

This tool targets the most frequent mistakes developers make when writing JSON by hand or copying data from other languages. It handles six categories of errors:

• Single quotes: JSON requires double quotes for strings and keys. Single quotes are replaced while preserving escaped characters inside them.
• Unquoted keys: Object keys must be quoted. Bare identifiers like name: are wrapped in double quotes.
• Trailing commas: A comma before a closing bracket or brace is illegal in standard JSON and is removed.
• Comments: Both line comments (//) and block comments (/* */) are stripped out.
• Python literals: The words True, False and None (when not part of a larger word) are converted to true, false and null.
• Missing brackets: If opening brackets or braces are left unclosed at the end of the input, the tool appends the necessary closing characters.

How the repair process works

The json fixer uses a character-by-character state machine rather than simple regular expressions. This matters because naive search-and-replace would corrupt strings that happen to contain comment markers or quote characters. The parser tracks whether it is currently inside a double-quoted string, a single-quoted string, a line comment or a block comment.

For example, consider the input {'url': "http://example.com"}. A regex replacing all single quotes would break the URL. The state machine recognizes that http://example.com is inside double quotes and leaves it untouched, while converting the outer single quotes around url and the value to double quotes. After all transformations, the result is passed through JSON.parse to verify validity. If parsing still fails, the tool reports the exact error instead of silently dropping data.

Common sources of invalid JSON

Invalid JSON usually comes from three places. First, manual editing in a text editor without linting leads to missing commas, extra commas or mismatched brackets. Second, copying data structures directly from Python, JavaScript or Ruby consoles produces output that looks like JSON but uses language-specific syntax such as single quotes, unquoted keys or undefined. Third, configuration files written in relaxed formats like JSON5 or JSONC include comments and trailing commas that strict parsers reject.

This json fixer bridges the gap between these relaxed formats and strict JSON. If you need to go further and convert your repaired JSON to other formats, tools like json to xml or json to sql can transform the valid output into the structure you need.

Reference table of fixes

The following table shows typical broken inputs and how the json fixer transforms them:

Limitations and edge cases

While this repair tool handles the vast majority of everyday JSON mistakes, some inputs cannot be fixed automatically. Deeply ambiguous syntax, such as a missing comma between two values where the boundary is unclear, may require human judgment. The tool also does not attempt to fix semantic errors like duplicate keys or incorrect data types; it only addresses syntax.

Unicode escape sequences like \u00e9 are preserved exactly as written. Strings containing escaped single quotes (\') inside single-quoted contexts are handled correctly by converting the escape to a plain single quote within the new double-quoted string. Empty input returns an error rather than producing an empty object, because guessing the intended structure would risk silently dropping data.

Worked examples