JSONGuy is a modern online JSON tool. It formats, validates, and repairs JSON — and, unlike most formatters, it accepts the JSON people actually write, not just strict JSON.
Pretty-print JSON with 2 or 4-space indent, GitHub-style syntax highlighting, and a collapsible tree view.
Catch syntax errors instantly, with the exact line and column of the problem.
Fix broken JSON — missing quotes, missing commas, and unclosed brackets — automatically.
Paste JSON5, JavaScript objects, or Python dicts — single quotes, unquoted keys, trailing commas, comments, None/True/False, tuples — and it normalizes everything into strict JSON.
Most JSON tools were built when JSON was a machine-to-machine format: strict, double-quoted, no comments. But most of the JSON people deal with today is hand-written or machine-generated and slightly wrong — Python dicts, JS object literals, LLM output with missing commas. JSONGuy was built around that reality: it reads the JSON humans actually write, and writes the strict JSON every system expects.
Formatting and validation run entirely in your browser — your JSON never leaves your device. The only time data is sent anywhere is when you explicitly use the share or publish features, which store it so the link can be served.
JSONGuy is open source under the MIT license — view the repository.