JSON Formatting and Validation Tools

8 tools · free · nothing uploaded

These are the tools for the two questions you ask before anything else: does this parse, and can I read it. Validation here is strict RFC 8259 — no trailing commas, no comments, no single quotes — and when it fails you get the line and column rather than "unexpected token".

Start here

JSON formatter Indent 2, 4 or tab, optionally sorting keys so two dumps of the same object diff clean. JSON validator Strict RFC 8259, with the line and column of the first thing that broke. JSON repair Trailing commas, single quotes, bare keys, smart quotes — the mess an LLM hands you. JSON minifier Strip every optional byte and see what you actually saved, gzipped as well as raw. JSON stringify Escape a document into a string literal you can paste into JS, Go, Python or a shell. Canonicalize + hash RFC 8785 byte-exact form plus its SHA-256 — what you hash before you sign.

Everything else in Format / Validate

JSON5 → JSON — Parse JSON5 (comments, unquoted keys, trailing commas) to strict JSON.
JSONC → JSON — Strip // and /* */ comments from tsconfig-style JSON.

Why these run in your browser

There is no server-side processing here and no upload step: the page loads, and from then on the parsing, converting and rendering happen in this tab using your machine's CPU. That has three consequences worth knowing about. Your data stays on your machine, which matters when the JSON is a production payload with real customer records in it. There is no file-size limit imposed by us, only by how much memory your browser will give the tab. And once the page has loaded, it keeps working with the network off.

The trade is that very large documents are bounded by browser memory rather than by a beefy server — somewhere past 50 MB a textarea gets sluggish, and dropping the file in is better than pasting it. The privacy page spells out what is and is not collected.