How to fix Error parsing JSON: invalid character in Terraform

Use a JSON validator to identify syntax errors. Check for missing commas, trailing commas, and unescaped characters.

# Use jq to validate a JSON file
jq . your-file.json

# Or use a built-in check
python3 -m json.tool your-file.json

If the validator shows an error, it will pinpoint the line and column. Look for:
- Missing commas between object properties
- Trailing commas (JSON doesn't allow them)
- Unescaped backslashes or quotes
- Single quotes instead of double quotes

The UTF-8 BOM (Byte Order Mark) or non-UTF-8 encoding is a common cause. On Linux/macOS:

# Check for BOM marker (shows 'EFBBBF' for UTF-8 BOM)
xxd -l 16 your-file.json

# Check file encoding
file your-file.json

# Remove BOM if present
sed -i '1s/^\xEF\xBB\xBF//' your-file.json

# Or use vim
vim your-file.json
# Then in vim: :set fileencoding=utf-8 :wq

On Windows, use a text editor like VS Code and:
1. Open the file
2. Click the encoding indicator (bottom right)
3. Select "UTF-8" (without BOM)

Look for hidden characters that the error message references. Use a hex dump to see raw bytes:

# Show hex dump with ASCII
hexdump -C your-file.json | head -20

# Search for the problematic character mentioned in the error
# If error says 'ï' (UTF-8 BOM first byte), look for EF BF

If you see unusual bytes (like C3 AF for the character 'ï'), the file has encoding issues. Re-save in UTF-8 without BOM.

If using JSON in template_body or similar fields, ensure variables and special characters are properly escaped:

# WRONG: Unescaped $ breaks JSON
template_body = jsonencode({
  properties = {
    value = "$variable"
  }
})

# CORRECT: Use Terraform variable interpolation
template_body = jsonencode({
  properties = {
    value = var.my_variable
  }
})

# Or escape if the $ is literal
template_body = jsonencode({
  properties = {
    value = "\$literal_dollar_sign"
  }
})

Use Terraform's jsonencode() function to safely convert HCL values to JSON.

If converting from HCL to JSON, ensure proper syntax:

# .tfvars (HCL format)
image_id = "ami-abc123"
availability_zones = ["us-west-1a", "us-west-1c"]

# .tfvars.json (JSON format) - must be valid JSON
{
  "image_id": "ami-abc123",
  "availability_zones": ["us-west-1a", "us-west-1c"]
}

Common mistakes:
- Single quotes instead of double quotes
- HCL comments (//, #) in JSON files
- Unquoted keys in JSON
- Trailing commas in JSON objects or arrays

Verify with: terraform validate

After fixing the file, validate your entire Terraform configuration:

terraform validate

This checks syntax across all .tf and .tfvars files. If it passes, the JSON parsing error is resolved.