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/AI JSON Error Explainer
14 error types · Auto-fix · RFC spec · 100% browser-only · no upload

AI JSON Error Explainer

Paste any broken JSON and get instant, plain-English explanations for every error at once — with RFC spec references and one-click auto-fix.

Live analysis One-click fix Diff view 14 error types RFC 8259 spec

Try an example →

JSON Input
1 L
1
0 chars
live · private · no upload
Analysis
🔍

Paste JSON to begin

Every error detected instantly — trailing commas, Python values, bad escapes, and 11 more.

What this tool detects

14 error types · auto-fix where possible · plain-English explanations

14 types
⚠️

Trailing Commas

✦ auto-fix
🐍

Python True/False/None

✦ auto-fix
🟡

NaN / undefined

✦ auto-fix
💬

JS Comments

✦ auto-fix
🔤

Single Quotes

✦ auto-fix
🔑

Unquoted Keys

✦ auto-fix
0️⃣

Leading Zeros

✦ auto-fix
➕

Plus Numbers

✦ auto-fix
📂

Unclosed Brackets

✦ auto-fix
⚡

UTF-8 BOM

✦ auto-fix
🔀

Mismatched Brackets

manual
🔁

Duplicate Keys

manual
🔴

Invalid Escapes

manual
🔋

Control Characters

manual

Related JSON tools

✨ JSON Beautifier🔧 JSON Fixer🔀 JSON Comparator📐 Schema Generator📦 JSON Stringify🔷 JSON → TypeScript✅ JSON Validator

What Is the AI JSON Error Explainer?

Most JSON debugging tools show you one error and stop. The AI JSON Error Explainer detects every error simultaneously, explains each one in plain English, references the exact RFC 8259 rule being violated, and provides one-click auto-fix for the most common issues.

Instead of cryptic messages like SyntaxError: Unexpected token ',', you get: what went wrong, why JSON forbids it, which language or tool likely produced it, how to fix it manually, and how to prevent it in JavaScript or Python code. All in your browser — nothing uploaded.

How it works

Deep Error Analysis in Seconds

01

Paste or load broken JSON

Type or paste any invalid JSON — AI output, Python dicts, JavaScript object literals, config files, truncated API responses, anything.

02

All errors detected instantly

Unlike JSON.parse() which stops at the first error, this tool finds every issue at once: trailing commas, wrong quotes, Python values, invalid escapes, duplicate keys, unclosed brackets, and more.

03

Read plain-English explanations

Each error card shows what went wrong, why JSON forbids it (with the RFC reference), how to fix it manually, and code examples in JavaScript and Python.

04

One-click auto-fix

Click "Fix all auto-fixable errors" to apply all safe fixes at once. A diff view shows exactly what changed. Apply to the editor or copy the fixed JSON.

Every JSON Error Type — Explained

Below is a complete reference for every error type this tool detects, with causes and fixes.

ErrorCauseAuto-fix
Trailing commaLast array/object element followed by ,✓ Auto-fix
Single quotesStrings wrapped in ' instead of "✓ Auto-fix
Unquoted keysJS-style { key: "value" } object literals✓ Auto-fix
Python valuesstr(dict) producing True/False/None✓ Auto-fix
JS-only valuesundefined, NaN, Infinity from JavaScript✓ Auto-fix
Comments// and /* */ from config files or AI output✓ Auto-fix
Leading zeros007, 0123 — octal-style number literals✓ Auto-fix
Plus-signed numbers+42 — valid in many languages but not JSON✓ Auto-fix
Unclosed bracketsMissing } or ] at end of file✓ Auto-fix
Mismatched brackets{ closed with ] instead of }– Manual
Duplicate keysSame key twice in one object– Manual
Invalid escape\x41, \p — not in the JSON escape set– Manual
Control charactersRaw ASCII 0–31 chars inside strings– Manual
UTF-8 BOM\uFEFF at start of file from some editors✓ Auto-fix
Use cases

When You Need This Tool

🤖

Fix AI-Generated JSON

LLMs frequently produce trailing commas, undefined values, and JS-style syntax. Paste the output, fix in one click.

🐍

Convert Python Dicts

When Python's str(dict) produces True/False/None, this tool explains why and fixes it with the json.dumps() alternative.

🟨

Parse JS Object Literals

Copy-pasted JavaScript objects with single quotes and unquoted keys are automatically detected and converted to valid JSON.

⚙️

Debug Config Files

JSONC config files with // comments fail in strict parsers. The tool strips comments and explains the difference between JSON and JSONC.

🔁

Find Silent Bugs

Duplicate keys cause silent data loss — parsers keep only the last value. This tool highlights every duplicate with exact line numbers.

📚

Learn JSON Rules

Each error card references the exact RFC 8259 clause being violated, with code examples in JavaScript and Python — perfect for learning.

FAQ

Frequently Asked Questions

1What does "Unexpected token" mean in JSON?
It means the parser found a character it did not expect. Common causes: trailing comma (,}), single-quoted string, a JS value like undefined, or an unquoted key. Paste your JSON here to get a specific explanation.
2Why does my JSON from Python have True, False, and None?
Python capitalises its booleans. When you use str(obj) on a dict, these appear in the output and break JSON parsers. Use json.dumps(obj) instead — it always produces valid, lowercase JSON.
3Why does AI-generated JSON have errors?
AI models train on JavaScript and Python code that allows trailing commas, single quotes, and undefined values. They sometimes apply those rules when generating JSON. Always validate AI output before parsing.
4Is my JSON data safe to paste here?
Yes. All analysis runs entirely in your browser — nothing is sent to any server. This is safe for API keys, tokens, and production data.
5What is a trailing comma in JSON?
A trailing comma is a comma after the last element in an array [1,2,] or the last key in an object {"a":1,}. JSON strictly forbids this, unlike JavaScript ES2017+ or JSON5.
6Why do duplicate keys cause problems?
The JSON spec says keys "should" be unique — so parsers don't error on duplicates. They silently keep only the last value, discarding earlier ones. This causes subtle, hard-to-debug data loss.
7Can JSON have comments?
No. Standard JSON has no comment syntax. For config files that need comments, use JSONC (VS Code supports it natively) or JSON5.
8What JSON escape sequences are valid?
Only these eight: \" \\ \/ \b \f \n \r \t and \uXXXX (4 hex digits). Anything else — like \x41 or \0 — is a syntax error in JSON even though it works in JavaScript.
Learn more

Developer Guides

📖Top 10 JSON Errors📖25 Broken JSON Examples📖Fix JSON Errors Guide📖Why JSON Breaks in APIs📖JSON Schema Guide

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