Paste your JSON and the tool checks it against the strict JSON rules, then shows it neatly indented or squeezed onto one line. If something is wrong you get the line and column of the first mistake, which saves you from hunting for a missing comma by eye.
JSON looks like a JavaScript object but is stricter. Every key must be a string in double quotes. Strings use double quotes with backslash escapes such as \n for a line break and \u00e9 for a Unicode letter. Numbers cannot start with a plus sign or a leading zero, and values like NaN, Infinity and undefined do not exist.
A raw tab or line break inside a string is also illegal; it must be written as an escape. This one is common in text copied from a word processor or a log, and the error appears at the line break rather than at the start of the string.
The line and column point at the first character that could not be accepted. When a value is missing a comma, the error shows at the start of the next item. When a string is not closed, the error is reported at the end of the text, because the scanner kept reading, looking for the closing quote.
Fix the first error and check again. Later messages can be side effects of the first one, such as a missing bracket making everything after it look wrong. Work from the top down rather than jumping to the last error.
A JSON formatter reads JSON text and writes it back with consistent indentation and line breaks so people can read it. The data stays the same; only the whitespace changes.
It checks the strict JSON grammar: objects with double-quoted keys, arrays, strings with valid escapes, numbers without leading zeros, and the words true, false and null. It reports the position of the first error it meets.
Format adds line breaks and indentation for reading. Minify removes all optional whitespace to make the text as short as possible for sending over a network or storing. A minified file and a formatted one hold identical data.
The scanner met a character that cannot appear at that point, such as a closing brace right after a comma or a word that is not true, false or null. The line and column point to that character, and the real mistake is usually just before it.
Numbers are read as ordinary floating-point values. Whole numbers above about 9 quadrillion lose exact precision, so keep long identifiers as strings in quotes if they must be exact.
Related: HTML table generator, Text to HTML converter, Schema markup generator.
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