Fix JSON Errors Online — AI-Powered Error Fixer
Paste broken JSON, get it fixed instantly with plain-English explanations. AI-powered repair for complex cases. 100% free, no sign-up.
Broken JSON
Fixed JSON
About JSON Error Fixer
Every developer has seen it: you paste JSON into your application and get a cryptic "SyntaxError: Unexpected token" error. The data looks fine at first glance, but somewhere in those nested brackets is an invisible problem — a trailing comma, a single quote, a raw newline character, or a missing closing brace. AllJSONTools' JSON Error Fixer finds and fixes these problems instantly. Paste your broken JSON, and the tool identifies every error by line number, explains what went wrong in plain English, and gives you corrected, valid JSON — ready to copy. For complex cases, AI-powered analysis goes beyond simple pattern matching to repair structural issues that regex-based tools miss. No sign-up, no server uploads for basic fixes, and completely free.
How to Use JSON Error Fixer
Paste Your Broken JSON
Paste invalid JSON into the editor. The tool auto-detects errors on paste — no button click needed. You can also drag and drop a .json file.
Review Errors & Fixes
Each error is listed with its line number, a plain-English explanation of what went wrong, and exactly how it was fixed. Click any error to jump to that line in the editor.
Copy the Fixed JSON
The corrected JSON appears in the output editor, ready to copy or download. Use the Quick Actions to convert it to TypeScript, YAML, or view it as a tree.
Common JSON Errors & How to Fix Them
These are the most frequent JSON syntax mistakes. Our tool detects all of them.
Trailing Comma
JSON does not allow trailing commas after the last property in an object or the last element in an array.
{ "name": "John", "age": 30, }{ "name": "John", "age": 30 }Single Quotes
JSON requires double quotes for all strings and keys. Single quotes are not valid.
{ 'name': 'John' }{ "name": "John" }Unquoted Keys
All object keys in JSON must be wrapped in double quotes, unlike JavaScript objects.
{ name: "John" }{ "name": "John" }Comments
Standard JSON does not support comments. Remove all // and /* */ comments.
{ "name": "John" // user name }{ "name": "John" }undefined / NaN
JSON does not support undefined or NaN. Use null for missing values.
{ "value": undefined, "count": NaN }{ "value": null, "count": 0 }Control Characters
Raw newlines, tabs, and other control characters inside strings must be escaped.
{ "text": "line1
line2" }{ "text": "line1\nline2" }For a comprehensive guide, read our article on fixing common JSON errors.
Common Use Cases
Fix API Response Errors
API responses with trailing commas, single quotes from Python backends, or truncated payloads — paste and fix instantly. Common when debugging REST or GraphQL APIs.
Repair Config Files
Fix tsconfig.json, package.json, .eslintrc.json and other config files that have comments (JSONC), trailing commas, or syntax errors from manual editing.
Clean Database Exports
Database dumps often contain control characters, raw newlines inside strings, or non-standard values like undefined and NaN. Auto-fix handles all of these.
Debug "Unexpected Token" Errors
When JSON.parse() throws "Unexpected token", this tool pinpoints the exact line and character, explains the cause, and fixes it — saving minutes of manual debugging.
Fix Webhook Payloads
Stripe, GitHub, and Slack webhooks sometimes arrive malformed due to encoding issues or truncation. Paste the raw payload and get valid JSON back.
Convert JavaScript Objects to JSON
JavaScript objects use unquoted keys, single quotes, and trailing commas — all invalid in JSON. This tool converts them to valid JSON automatically.
Why Use Our JSON Error Fixer?
AI-Powered Fixing
Goes beyond regex pattern matching to repair complex structural issues that other tools miss
Plain-English Explanations
Every error is explained in human language, not just "Unexpected token at position 42"
Line-by-Line Diagnosis
Click any error to jump directly to the problem line in the editor
Auto-Fix on Paste
Paste broken JSON and get it fixed instantly, no extra clicks needed
Privacy-First
Basic fixes run 100% in your browser. AI fixes send only the minimum data needed
100% Free
No account, no rate limits on basic fixes, no premium tier for core functionality
Key Features
Auto-fix on paste — broken JSON is repaired the moment you paste it
AI-powered repair for complex cases that regex cannot handle
Plain-English error explanations for every issue found
Click-to-jump error navigation — click an error to go to that line
Error highlighting with red markers in the Monaco editor
Handles trailing commas, single quotes, unquoted keys, and comments
Escapes bad control characters (raw newlines, tabs) in string values
Replaces undefined, NaN, and Infinity with valid JSON equivalents
Auto-closes unclosed brackets and braces from truncated data
Copy fixed JSON, download as .json, or share via URL
100% Client-Side Processing
Your data never leaves your browser
All processing happens in your browser using JavaScript. Your data is never sent to our servers or any third party. Safe for sensitive data, API keys, and production configs.
Frequently Asked Questions
Quick answers to common questions about json error fixer
This is the most common JSON error. It means the parser found a character it didn't expect — usually a trailing comma, single quote, comment, or unquoted key. Our tool pinpoints the exact character and fixes it automatically.
JSON does not allow commas after the last property in an object or the last element in an array. For example, {"a": 1,} is invalid. Remove the comma before } or ]. Our tool detects and removes all trailing commas automatically.
The JSON specification (RFC 8259) requires all strings and keys to use double quotes. Single quotes are valid in JavaScript but not in JSON. This tool converts all single quotes to double quotes while preserving apostrophes inside values.
Standard JSON (RFC 8259) does not support comments. JSONC (JSON with Comments) is a variant used by VS Code configs and TypeScript configs, but it is not valid JSON. This tool strips // and /* */ comments to produce valid JSON.
This error occurs when a JSON string contains raw control characters like newlines (char code < 0x20). These must be escaped as \n, \t, \r, etc. This commonly happens when JSON is copied from databases, log files, or spreadsheets. Our tool escapes them automatically.
This means the JSON data is incomplete — usually missing closing brackets }, ], or quotes. It often happens with truncated API responses or incomplete copy-paste. Our tool auto-closes unclosed brackets to produce valid JSON.
Basic fixes (trailing commas, single quotes, comments, etc.) run 100% client-side in your browser — your data never leaves your device. AI-powered fixes for complex cases send the minimum data needed to the AI model, and nothing is stored or logged.
JSON formatting takes already-valid JSON and makes it readable with proper indentation. JSON fixing takes invalid/broken JSON and repairs syntax errors to make it valid. Use the formatter for readability, use this fixer when JSON.parse() throws an error.
Yes. Python dicts use single quotes, True/False instead of true/false, and None instead of null. All three are automatically converted to valid JSON equivalents.
Basic fixes (90%+ of cases) run entirely in your browser with no AI and no cost. AI is only used for complex structural repairs that regex cannot handle. AI fixes are free with a fair-use rate limit of 10 per hour.
Learn More
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Fix Common JSON Errors
A comprehensive guide to the 9 most frequent JSON syntax mistakes and how to fix them.
< / >
How to Parse JSON in JavaScript
Learn JSON.parse(), JSON.stringify(), error handling, and best practices.
=> { }
JSON API Best Practices
Design better JSON APIs that produce valid, consistent responses.
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