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Fix "Invalid control character" JSON Error

Complete guide to fixing control character errors

The "Invalid control character" error occurs when JSON contains unescaped control characters like newlines, tabs, or other special characters that must be escaped in JSON strings.

Control characters (newlines \n, tabs \t, etc.) must be properly escaped in JSON. Learn how to fix this instantly using our free JSON Fixer tool.

What Are Control Characters?

Control characters are special characters that control text formatting:

  • \n - Newline
  • \t - Tab
  • \r - Carriage return
  • \b - Backspace
  • \f - Form feed

Broken JSON Example

❌ Broken JSON (Unescaped Newline):

{
  "message": "Line 1
Line 2"  ← Unescaped newline
}

Error: Invalid control character in JSON

✅ Fixed JSON:

{
  "message": "Line 1\nLine 2"
}

Fix Control Character Errors — Try It Below

Our tool auto-escapes control characters so your JSON parses cleanly.

Fix "Invalid Control Character" JSON Error

Control characters are ASCII characters with codes 0–31. Common examples include tab ( or \t), newline ( or \n), carriage return ( or \r), and null (\0 or \u0000). The JSON specification requires that these characters appear inside strings as their escape sequences — raw control characters are strictly forbidden.

When a raw control character slips into a JSON string — usually from copy-pasted terminal output, log files, or user-supplied text — JSON parsers throw an "Invalid control character" error. The auto-fixer scans the input, finds unescaped control characters, and replaces them with the correct escape sequences.

How to fix

Fix This JSON Error in Seconds

01

Paste your broken JSON

Paste the JSON with the error into the JSON Fixer above.

02

Error is highlighted

The tool shows the exact line and character where the error is detected.

03

Click Auto-Fix

The auto-fixer escapes all raw control characters to their valid JSON escape sequences.

04

Copy fixed JSON

Copy the valid JSON output — or switch to the JSON Beautifier for formatting.

FAQ

Frequently Asked Questions

1Why does JSON.parse() throw "Invalid control character" when I paste terminal output into a string?
Terminal output and log files often contain raw control characters like newlines, tabs, and null bytes. When pasted directly into a JSON string without escaping, the parser throws this error. Always use JSON.stringify() to serialize values containing user or terminal input — it escapes these characters automatically.
2Why does the invalid control character error happen?
It usually occurs when JSON is generated from user input, terminal output, or a text editor that includes raw newlines, tabs, or null bytes inside strings without escaping them first.
3How do I prevent control character errors in the future?
Always serialize JSON using a proper library — JSON.stringify in JavaScript or json.dumps in Python. These libraries automatically escape control characters. Avoid building JSON strings manually using string concatenation.
Learn more

Related Guides

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

Last updated: May 2026

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