JSON Formatter & Validator

JSON (JavaScript Object Notation) is the de facto data-interchange format of the modern web — REST APIs, configuration files, log entries, and the payloads passed between almost every frontend and backend all use it. Its two biggest practical problems are also its biggest strengths taken too far: because whitespace is optional, a JSON payload can be minified down to the smallest possible number of bytes for transmission, but that same minified form is nearly unreadable to a human trying to debug what an API actually returned. This tool solves both directions of that problem with one paste box. Format takes any valid JSON and re-serializes it with 2-space indentation and one key or array element per line, which is the layout most style guides and most editors default to. It also applies lightweight syntax highlighting — strings in green, keys in purple, numbers in blue, booleans in orange, and null in grey — using a plain regular-expression tokenizer rather than a heavyweight syntax-highlighting library, so the page stays fast even on large payloads. Minify does the opposite: it strips every unnecessary space, tab and newline, producing the smallest valid representation of the same data, which is exactly what you want before pasting a payload into a size-constrained field (a URL query parameter, a database column with a length limit, a request body you are trying to keep under a size threshold). Validate is a dedicated third mode for when you only want a yes/no answer plus a location, without needing to see reformatted output. It reports the browser's own `JSON.parse` error message, which — since Chrome 116/Firefox 119 era engines — typically includes the line and column of the first problem (for example, a trailing comma, an unquoted key, or a missing closing brace). That built-in error message is written by the same engine that will eventually consume the JSON in a real application, so it is a more reliable signal than a third-party linter that might parse JSON slightly differently. A common point of confusion: JSON is stricter than JavaScript object literal syntax, even though it looks almost identical. Trailing commas after the last item in an array or object are invalid in JSON (they are allowed in modern JavaScript), keys must always be double-quoted strings (single quotes and unquoted keys are both invalid), and comments are not permitted anywhere in a JSON document, even though many JavaScript-adjacent config formats (JSON5, JSONC used by VS Code's settings files) do allow them. If your input fails validation and looks correct at a glance, checking for these three things first — trailing commas, unquoted/single-quoted keys, and stray comments — resolves the large majority of "but this looks fine" JSON errors. Because everything runs client-side, this tool is safe to use on real API responses and configuration files that may contain access tokens, internal URLs or other sensitive values you would not want to paste into a third-party server — nothing you type here is transmitted, logged, or stored.