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JSON Studio — Formatter & Validator

Paste JSON to format, minify or validate it instantly. Errors are shown with the exact line, column and cause, and comments or trailing commas can be auto-repaired. Your data never leaves your device.

On-device・No upload

Your files and input are processed only inside your browser on this device and are never uploaded to our servers.

Input JSON
0 chars0 lines
ResultEnter JSON and the result appears here
Enter JSON and the result appears here

How to use

  1. Paste JSON into the input pane, or click “Open file” to load a .json file (drag & drop works too).

  2. Choose a mode: Format, Minify, Tree view or String escape. The result updates as you type.

  3. Adjust indentation, key sorting or non-ASCII escaping if needed.

  4. If there is an error, check the reported line and column, use “Go to error” to jump there, and try “Auto-repair and retry” if appropriate.

  5. Copy the result or download it as a file.

What it does

Lossless number handling

Tools built on JSON.parse round integers above 9,007,199,254,740,991 (2^53 − 1) and long decimals. Our own parser keeps every number exactly as written, so order IDs and other large values never change.

Precise error reporting

Syntax errors show the line, column, what was expected and what was found, with a marked excerpt. “Go to error” selects the exact spot in the editor.

Auto-repair for JSONC / JSON5-style input

Converts comments, trailing commas, single quotes, unquoted keys and NaN/Infinity into valid JSON — and lists every repair it made.

Tree view with path copy

Explore large documents in a collapsible tree and copy the JSONPath of any value (e.g. $.items[0].sku) in one click.

Duplicate key detection

Flags repeated keys, which JSON technically allows but which often cause subtle bugs.

Stays responsive with big files

Processing runs in a background Web Worker, so multi-megabyte JSON does not freeze the page.

Use cases

  • Make an API response or config file readable
  • Find the exact cause of an “Unexpected token” error
  • Turn JavaScript objects or commented JSONC into valid JSON
  • Format JSON containing 64-bit IDs without losing digits
  • Embed text with line breaks and quotes as a JSON string

Supported formats

Input

JSONJSONC (comments)JSON5-style syntax (auto-repair).json.geojson.webmanifest.mapUTF-8 / UTF-16 (with BOM)

Output

Formatted JSON (2 / 4 spaces, tab)Minified JSON (one line)JSON string literal

Capability matrix

FeatureSupportNotes
Format & minify (2 / 4 spaces, tab)Supported—
Syntax validation with line/columnSupported—
Exact large numbers (integers above 2^53, long decimals)SupportedOutput exactly as written
Auto-repair comments, trailing commas, etc.SupportedRepairs are listed
Sort keys alphabeticallySupportedApplied to nested objects
Tree view & JSONPath copySupported—
Duplicate key detectionSupported—
JSON Schema validationNot supportedSyntax only
JSON Lines (one JSON per line)Not supportedTreated as one document; extra lines are errors
Offline useSupportedWorks without a connection once loaded

Limits & notes

  • Files up to 50 MB can be loaded. Above one million characters, auto-run pauses and you press “Run”.
  • Nesting is limited to 1,000 levels to keep the browser from hanging on pathological input.
  • The tree view shows 200 entries per level at a time (use “Show more”).
  • Key sorting uses code-point order, not numeric order.
  • Auto-repair involves guesses — always review the repaired output.

Privacy & safety

Your JSON and files are processed only inside your browser. Nothing is sent to or stored on any server, so you can safely format data that contains API keys or personal information. Closing the page discards everything.

FAQ

How do I fix an “Unexpected token” JSON error?
It is usually a missing or extra comma, a missing closing bracket, or an unclosed string quote. Paste the JSON here to see the line, column and expected character. If comments or trailing commas are the cause, “Auto-repair and retry” fixes them.
Why do large numbers (IDs) change in other tools?
JavaScript numbers are exact only up to 9,007,199,254,740,991 (15–16 digits), so tools using JSON.parse round values like 9007199254740993. This tool keeps numbers as text, so formatting never changes them.
Can it handle JSON with comments (JSONC)?
Yes. Turn on “Auto-repair” and // or /* */ comments are removed, producing valid JSON — handy for files like tsconfig.json.
Is my data sent to a server?
No. Everything runs in your browser; your input is never sent to LIBRA Works or any third party.
What is the difference between formatting and minifying?
Formatting adds line breaks and indentation for readability; minifying removes unnecessary whitespace to make the file smaller. The data itself does not change.

Related tools

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Paste XML to format, minify or validate it. Errors show the exact line, column and cause, and whitespace that carries meaning (mixed content, xml:space) is never touched. XPath search and JSON conversion are on the same screen. Your data never leaves your device.

YAML / TOML Studio — Validate, Format & Convert

Paste YAML, TOML or JSON to validate, format or convert it. Errors show the exact line and column, and type traps such as “no becomes false” and anything lost in conversion are flagged up front. Your data never leaves your device.

Diff Tool — Text & Code Compare

Paste or drop two versions and see added and removed lines, plus the exact words that changed inside each line. Copy or save the result as a unified patch. Nothing leaves your browser.

UUID / ULID / NanoID / Token Generator

A UUID is ready the moment the page opens. Switch to UUID v7, ULID, NanoID or a random token, generate up to 10,000 at once and save them as .txt, .csv or .json. Paste an existing UUID or ULID to read its embedded time and version.

Regex Tester

Type a pattern and matches light up in the test string instantly. Capture groups, replacement output and what each part of the pattern means are all on one screen — and patterns that would freeze your browser are stopped after one second.

Code Formatter — Format & Minify

Paste code to format it with the language auto-detected. Choose indent, line width, semicolons, quotes and trailing commas; JavaScript, CSS and HTML can also be minified with before/after size and reduction. Your code never leaves the browser.

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