I Built an AI-Powered JSON Error Fixer — Here's How It Works

Fenil Panwala — Thu, 19 Mar 2026 11:31:44 +0000

Every developer has seen this error…

SyntaxError: Unexpected token } in JSON at position 127

And that’s it.

No context.
No hint.
Just vibes.

You end up staring at 200 lines of JSON trying to find one missing comma like it’s a Where’s Waldo puzzle.

😤 The Problem

JSON errors are painfully unhelpful:

No line numbers (most of the time)
No explanation of what actually went wrong
Just a position index that means nothing in real life

So debugging turns into:

“Let me just scroll… scroll… scroll… oh wait… nope… still broken.”

💡 So I built a tool

👉 Paste broken JSON → get it fixed instantly

🔧 https://alljsontools.com/fix-json-error

⚡ What It Does

🧠 Client-side fixes (instant, no API)

Handles most common issues right in the browser:

Trailing commas
{"a": 1,} → {"a": 1}
Single quotes
{'a': 1} → {"a": 1}
Unquoted keys
{name: "John"} → {"name": "John"}
JS-style comments
{"a": 1 // note} → {"a": 1}
Invalid values
undefined, NaN → null
Control characters
Raw newlines → escaped \n
Mismatched brackets
[1, 2, 3} → [1, 2, 3]

🤖 AI fixes (for complex cases)

When regex hits its limits, AI steps in.

You also get a human-readable explanation:

Line 5: Trailing comma before } — JSON doesn't allow commas after the last property. Removed.

⚙️ How It Works (Under the Hood)

The fix pipeline runs step-by-step:

Escape control characters
Strip comments (string-aware, not naive regex)
Convert single → double quotes
Quote unquoted keys
Remove trailing commas
Replace invalid values (undefined, NaN)
Fix bracket mismatches (stack-based)
Quote unquoted values
Attempt JSON.parse()

If it still fails → AI fallback.

🧩 The tricky part: Comment stripping

Naively doing this breaks URLs:

// ❌ This will break https://example.com
text.replace(/\/\/.*$/gm, '')

So I wrote a character-by-character parser that tracks string state:

for (const line of text.split('\n')) {
  let inString = false;
  let escaped = false;
  let commentStart = -1;

  for (let i = 0; i < line.length; i++) {
    if (escaped) {
      escaped = false;
      continue;
    }

    if (line[i] === '\\' && inString) {
      escaped = true;
      continue;
    }

    if (line[i] === '"') {
      inString = !inString;
      continue;
    }

    if (!inString && line[i] === '/' && line[i + 1] === '/') {
      commentStart = i;
      break;
    }
  }

  // Only strip if // is outside a string
}

🤖 AI Fallback Details

Max input: 50KB
5 free AI fixes/day
Output is validated using JSON.parse()
Markdown fences (`json) are stripped automatically

🧰 Tech Stack

Next.js 16
React 19
TypeScript (strict)
Monaco Editor (VS Code engine)
Web Workers for files >5MB

🧪 Testing

361 unit tests, including:

__proto__ pollution prevention
ReDoS-safe regex
5MB payload performance
AI response parsing

🔗 Try It

🔧 Fix JSON errors: https://alljsontools.com/fix-json-error
🏠 All tools: https://alljsontools.com

Everything is free. No signup.
Core tools work 100% client-side (even offline).

🙌 Feedback?

Would love to hear:

Edge cases I might’ve missed
Performance issues
Weird JSON you've encountered in the wild

💬 Question for you

What’s the weirdest broken JSON you’ve ever debugged?

How to Convert JSON to CSV for Excel (With Example)

Fenil Panwala — Sun, 22 Feb 2026 18:31:35 +0000

APIs and modern applications usually return data in JSON format, but tools like Microsoft Excel and Google Sheets work much better with CSV files.

If you’ve ever tried to open raw JSON in Excel, you already know how messy it can get.

In this article, I’ll show:

What JSON and CSV are
A simple JSON → CSV example
Different ways to convert JSON to CSV

What is JSON and CSV?

JSON (JavaScript Object Notation)
JSON is a structured data format commonly used by APIs and web services. It supports nested objects and arrays.

CSV (Comma-Separated Values)
CSV is a flat, tabular format that works well with Excel, Google Sheets, and data analysis tools.

Because CSV is flat, JSON data often needs to be flattened during conversion.

Example JSON Data

[
  {
    "id": 1,
    "name": "John Doe",
    "email": "john@example.com",
    "skills": ["JavaScript", "React"]
  },
  {
    "id": 2,
    "name": "Jane Smith",
    "email": "jane@example.com",
    "skills": ["Java", "Spring"]
  }
]

Converted CSV Output

id,name,email,skills
1,John Doe,john@example.com,"JavaScript|React"
2,Jane Smith,jane@example.com,"Java|Spring"

This CSV file can be opened directly in:

Microsoft Excel
Google Sheets
LibreOffice Calc

Ways to Convert JSON to CSV

Writing a Script You can write a script in JavaScript, Python, or another language to parse JSON and generate CSV.

Pros

Full control over transformation
Custom logic for complex data

Cons

akes time to write and maintain
Overkill for quick conversions

Using Excel Power Query Excel allows importing JSON using Power Query.