How to format and validate JSON

What JSON validation checks

JSON is stricter than JavaScript. Keys and strings need double quotes, a document cannot end an object or array with a trailing comma, and comments are not allowed.

A validator reads the whole document and stops at the first problem it finds, so fix errors from the top down and check again.

Reading an error message

The line and column in the error point to the character where the parser could not continue. The real mistake is often just before that point, such as a missing comma on the line above.

Format for reading, minify for sending

Indentation makes nested data easy to scan. Minified JSON removes the whitespace, which makes it smaller for APIs and configuration values. Both forms contain exactly the same data.

Keep large files manageable

Formatting a very large document is slow in any browser, so the formatter accepts up to 1 MB of text. For bigger files, use a command-line tool such as jq on your own machine.