What causes "YAMLException: bad indentation of a mapping entry at line X"?

Mixed tabs and spaces in the YAML file Inconsistent indentation levels (e.g., 2 spaces in one place, 4 in another) A list item (-) not aligned with its siblings Copy-pasting from a source that used tabs

YAML Error3 Fixes Available

YAMLException: bad indentation of a mapping entry

YAMLException: bad indentation of a mapping entry at line X

What does this error mean?

YAML is extremely sensitive to indentation. This error means a key-value pair (mapping entry) is not indented consistently with the rest of the block. YAML uses spaces (never tabs) for indentation.

Common Causes

Mixed tabs and spaces in the YAML file
Inconsistent indentation levels (e.g., 2 spaces in one place, 4 in another)
A list item (-) not aligned with its siblings
Copy-pasting from a source that used tabs

How to Fix It (3 Solutions)

Use our YAML Validator

Paste your YAML into our validator to instantly see the exact line and column of the error.

Replace all tabs with spaces

YAML does not allow tabs. Use your editor's 'Replace All' to convert tabs to spaces.

Code

# In VS Code: Open Command Palette → "Convert Indentation to Spaces"
# Or use sed on Linux:
sed -i 's/\t/  /g' your-file.yaml

Use consistent 2-space indentation

Stick to 2 spaces per indentation level throughout the entire file.

Code

# ✅ Correct
services:
  web:
    image: nginx
    ports:
      - "80:80"

# ❌ Wrong (mixed indentation)
services:
  web:
      image: nginx  # 6 spaces instead of 4

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YAML duplicate key warning

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