Paste a wall of JSON and make it readable again. The Gizmo 421 JSON Formatter validates, pretty-prints, and minifies — with a hand-built parser that points at the exact line and column where your JSON breaks, instead of a shrug.
The validator is a real recursive-descent parser — tokenizer, strings with full escape handling, strict number grammar — not a try/catch around a browser function. That’s why the errors are actually helpful: a missing comma reports “Expected ‘,’ or ‘}'” with the line and column, and an unterminated string tells you where it started. Formatting uses two-space indentation with proper empty-object and empty-array handling, and minify strips it all back to one line for shipping.
Is my JSON sent to a server? No — parsing and formatting happen entirely in your browser, which makes this safe for API responses you’d rather not paste into random websites. What counts as valid JSON? Double-quoted strings, no trailing commas, no comments — strict JSON. Does it handle Unicode escapes? Yes, \u sequences decode properly on both parse and output. Format or minify — which do I need? Format to read or debug, minify to ship; same data, different wardrobe.