Fix Invalid JSON: From 'What's Wrong' to a Clean File

Repair JSON that looks almost right — trailing commas, single quotes, unquoted keys — using a smart formatter that tolerates almost-JSON and then validates strictly.

When you land here

You have a JSON file that almost works. The parser rejects it, but the structure is clearly readable. This hub points to the smart-repair workflow that handles the most common almost-JSON mistakes, plus the strict validator that confirms the cleaned file before you ship.

Repair and format broken JSONValidate JSON strictly (RFC 8259)Minify the cleaned JSONDiff before-and-after to confirm the cleanup

The four mistakes that cover 90% of broken JSON

Almost every invalid-JSON ticket is one of trailing commas, single quotes, unquoted keys, or a stringified object printed where parsed JSON was expected. Each has its own guide.

Fix trailing commas in JSONFix single quotes in JSONFix unquoted keys in JSON[object Object] is not valid JSONJSON formatter vs JSON repair — when to use which

When repair isn't safe

Auto-repair guesses are safe for quote-style and trailing commas, but unsafe for missing keys, missing brackets, or ambiguous numbers. Treat repair as a syntax assistant; validate the business contract afterward.

Validate JSON before API requestsCompare two JSON filesRepair broken JSON in JavaScriptFix JSON online (workflow)Trailing comma in JSON (full breakdown)

Repair locally, not on someone's server

Recent incidents have shown that pasting JSON into a third-party formatter leaks the contents. The repair, validation, and minify workflows on this site run entirely in your browser tab — nothing is uploaded.

Online JSON formatter data leak (Snyk research)jq NUL-byte validation bypass (CVE)jq path-depth CVE in JSON pipelines

Recommended path

From the broken text to a clean file in four steps.

  • 1. Tool: / — paste the broken JSON, click Repair & Format.
  • 2. Guide: /guides/json-formatter-vs-json-repair — confirm which mode you actually need.
  • 3. Blog: /blog/fix-json-online — full walkthrough.
  • 4. Reference: /news/online-json-formatter-data-leak — why local processing matters.
Open JSON FixCompare JSON changes

JSON repair guides

Topic hubs

  1. JSON Parse Errors: Read the Message, Jump to the Fix
  2. JSON Formatter, Validator, Viewer: Pick the Right Tool
  3. Repair LLM JSON Output: Handling Almost-JSON from AI
  4. Privacy: JSON Tools That Don't Leave Your Browser
  5. JSON Interop: YAML, CSV, XML, JWT, Schema

Specific guides

  1. How to Decode Base64 Strings (and JWT Payloads)
  2. URL Encoding: Percent-Encode Query Parameters and Paths
  3. Convert YAML to JSON (and Avoid Indentation Errors)
  4. Convert JSON to CSV: Flatten an Array of Objects
  5. Convert JSON to XML: Root Elements, Attributes, and Arrays
  6. Escape JSON as a String Literal (and Decode Double-Encoded JSON)
  7. Fix Trailing Comma in JSON
  8. Fix Single Quotes in JSON
  9. Fix Unquoted Keys in JSON
  10. Repair LLM JSON Output
  11. Fix JSON Parse Error: Expected Property Name
  12. JSON vs JS Object Literal: The Key Differences
  13. Validate JSON Before API Requests
  14. JSON Formatter vs JSON Repair
  15. Fix JSON Unexpected Token Errors
  16. JSON to JavaScript Object Converter