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Format, validate, and explore JSON without sending it anywhere
JSON shows up in API samples, appsettings files, browser payloads, and log lines that were never meant to be read as a single wrapped paragraph. A missing comma or an extra trailing comma is enough to stall a client. A formatter that pretty-prints without rewriting values, reports the first syntax error with a line and column, and can jump to that spot is faster than scrolling a minified blob. Minify is the other direction: a compact payload for a fixture or a request body. A tree is how you copy users[0].name without counting brackets by hand.
Why this is worth doing in the browser
Desktop editors highlight well and still leave you hunting the first parse error. Online formatters often upload the payload. The DevNestro JSON Formatter, Validator & Viewer keeps the work in this browser. Paste or upload a .json or .txt file up to the configured size; oversized files are rejected, not truncated. Choose 2 spaces, 4 spaces, or tabs. Format, validate, or minify. Invalid JSON gets a readable message, a Go to Error control, and a fixer that previews trailing commas, single quotes, unquoted keys, comments, and missing brackets when the repair is unambiguous. Ambiguous input is left alone with cannot be safely repaired automatically. Sort keys A to Z or Z to A on the current object or recursively; arrays keep their order. Search keys, values, or raw text with a match count. Copy a JavaScript path or JSONPath from the tree. Table view appears only for an array of similar objects. Large JSON warns, skips auto-format, and delays search so the tab stays usable. Continue to Universal Data Converter, Diff Checker, Secret Leak Inspector, or JSON to C# when you need conversion, a diff, a secret scan, or generated types.
How to use the tool
Paste or upload the payload you actually have. Validate first if you only need to know whether it parses. Format when you want indented output you can read or commit. Open the tree to copy a path or a subtree. If the fixer lists repairs, preview them, apply one, or apply all. Download uses a fixed local filename and does not upload the file.
- Paste the payload you received, not a guessed subset, and keep Unicode as it arrived.
- Validate when the API looks fine but the client still throws, then use Go to Error.
- Format before you commit a fixture so the diff is readable; minify only when you need a compact body.
- Use the fixer for trailing commas and comments; stop if it says the JSON cannot be safely repaired automatically.
- Copy a path from the tree instead of typing it, and clear the editor if the payload should not stay on screen.
Privacy
Formatting, validation, repair, search, and downloads run in the current browser. JSON is not uploaded to DevNestro, not stored as a catalogue of API responses, and not sent to analytics. There is no account.
Stop hunting a missing comma in a minified line. Open the JSON Formatter, validate, pretty-print or repair with a preview, and copy something a human can read.