JSON Formatter & Validator

JSON Formatter is a fast, offline JSON tool for Android. Paste a response, open a file, and get it formatted, checked and explained — without sending your data anywhere.

It does not rewrite your numbers

Most formatters parse JSON into their language's own number type and print it back out. That quietly changes your document: 12345678901234567890 becomes 12345678901234567000, 1e5 becomes 100000.0, 1.50 becomes 1.5, and -0 becomes 0. This app keeps every number exactly as it was written, because a formatter that edits your data is not a formatter.

It tells you where the problem is

Invalid JSON gets a plain-English reason, the exact line and column, and a button that puts your cursor there. No "unexpected token" with nothing to go on.

It finds duplicate keys

{"timeout": 30, "timeout": 5} is legal JSON, and almost every reader keeps only the last value and says nothing — so half of your config is silently ignored. This app keeps both, flags them, and shows you the path.

It reads real-world files

Config files have // comments, trailing commas, single quotes and unquoted keys. Turn on relaxed parsing and it reads them, outputs strict JSON, and lists every deviation it tolerated — so you find out your file was never valid JSON in the first place.

Explore, don't scroll

The tree view collapses and expands objects and arrays, shows types and child counts, and copies the path to any value ($.servers[2].host) or the value itself.

Everything else

• Output as 2 spaces, 4 spaces, tabs, or minified to one line

• Sort object keys alphabetically, the way jq -S does

• Optionally escape every non-ASCII character

• Line numbers, indent guides and syntax colours tuned for light and dark

• Follows your system theme, or pick light or dark yourself

• Copy or share the result

• Your last 20 documents, kept on the device

• Handles files up to 8 MB, parsed off the UI thread so it stays responsive

• 10 languages: English, German, Spanish, French, Italian, Portuguese, Russian, Turkish, Japanese and Chinese

Privacy

Your documents are parsed on this device and are never uploaded — there is no account, no sync and no server. Saved documents are excluded from cloud backup. The app shows ads and uses Google Analytics for Firebase and Crashlytics; nothing it reports ever contains your document, a key name or a file name. In the EEA and the UK you are asked for ad consent before any personalised ad is requested, and you can change that answer at any time from Settings.

Built by a developer who got tired of pasting company data into a website to indent it.