JSON Formatter & Validator
Local processing · never uploadedFormat, validate & minify JSON — right in your browser.
What is JSON Formatter & Validator?
JSON Formatter & Validator is a fast, free online JSON formatter that turns messy or minified JSON into clean, readable, properly indented text — and tells you exactly where the syntax breaks when something is wrong. Use it as a JSON beautifier online, a JSON validator, or to pretty-print JSON in one click. It also brings AI to JSON: repair broken JSON automatically, and generate typed code from any JSON sample.
JSON (JavaScript Object Notation) is the most common format for APIs, configuration files and data exchange between services. But raw JSON is often delivered on a single line or with inconsistent spacing, which makes it nearly impossible to read or debug. This tool parses your input, validates it against the JSON specification, and re-serialises it with the indentation you choose (2 spaces, 4 spaces or tabs). You can also minify JSON back down to a single line to save bytes before shipping it to production.
When your JSON is invalid, the validator pinpoints the exact line and column of the first error and explains in plain language what went wrong — a missing comma, an unclosed string, a trailing bracket — so you can fix it in seconds. For broken JSON that a human would have to untangle by hand, the built-in AI Repair parses the intent of the text, fixes the syntax and lists every change it made, so you can review before applying it.
Once your JSON is valid, the Generate Code feature turns it into typed definitions with one click: JSON to TypeScript interfaces, JSON to Java classes or records, Python dataclasses, Go structs, Rust structs, C++ classes and C# classes. The AI generates idiomatic, ready-to-paste code with correct field names and types — ideal for building API clients, mapping database rows or scaffolding model classes from a sample response.
Formatting, validation, minifying and tree editing all run entirely in your browser using the native JSON engine, so your data is never uploaded, logged or stored. The AI Repair and Generate Code features send your JSON to our server for that single action (3 free runs per IP per day); every other tool on ToolPie stays 100% local, which makes it safe to use even with sensitive payloads like API responses, tokens or internal configuration.
FAQ
Is my JSON data uploaded to a server?
Formatting, validation, minifying and tree editing all run locally in your browser using the native JSON engine, so your data never leaves your device. Only the optional AI Repair and Generate Code features send your JSON to the server for that single action — you are prompted the first time you use them.
What does "Validate" tell me?
It checks whether your text is valid JSON. If not, it shows the exact line and column of the first error with a plain-language explanation (for example, a missing comma or an unclosed string).
Can the AI repair my broken JSON?
Yes. AI Repair parses text that is not valid JSON — unquoted keys, trailing commas, single quotes, comments, cut-off objects — fixes the syntax and shows a summary of every change, with 3 free repairs per IP per day. You review the result and apply it only when you are happy.
Can it convert JSON to TypeScript, Java, Python, Go, Rust, C++ or C#?
Yes. Once your JSON is valid, Generate Code turns it into TypeScript interfaces, Java classes (or records), Python dataclasses, Go structs, Rust structs, C++ classes and C# classes. You pick the language, optionally a root class name, and the AI produces idiomatic, ready-to-paste typed code.
Can I choose the indentation?
Yes. You can format with 2 spaces, 4 spaces or tabs, and your preference is remembered for next time.
What is the difference between Format and Minify?
Format (beautify) adds indentation and line breaks to make JSON readable. Minify removes all unnecessary whitespace to produce the smallest possible single-line output.
Is there a size limit?
Local formatting and validation have no hard limit, but very large inputs (over ~2 MB) switch to manual mode to keep the page responsive. The AI Repair and Generate Code features accept up to 16 KB per request, which covers typical API responses and config files.
Does it support comments or trailing commas?
Strict JSON does not allow comments or trailing commas, so by default they are reported as errors. This keeps your output spec-compliant. (AI Repair can still recover text that contains them.)