JSON, XML & YAML Error Messages
Comprehensive guide to common parsing errors and how to fix them. Find your error message below for instant solutions.
💡 Quick Fix Tips
{ } JSON Errors
SyntaxError: Unexpected token
The parser found a character that doesn't belong in valid JSON at the specified position.
Common Causes:
- Trailing comma after the last element
- Single quotes instead of double quotes
- Unquoted property names
- Comments in JSON (not allowed)
- Missing comma between elements
❌ Wrong
{
"name": "John",
"age": 30, // trailing comma!
}✓ Correct
{
"name": "John",
"age": 30
}SyntaxError: Unexpected end of JSON input
The JSON string ended before all structures were properly closed.
Common Causes:
- Missing closing brace }
- Missing closing bracket ]
- Incomplete string (missing closing quote)
- Empty input string
❌ Wrong
{
"users": [
{"name": "John"}
// missing ] and }✓ Correct
{
"users": [
{"name": "John"}
]
}SyntaxError: Expected property name or }
An object was expected to have a property name but found something else.
Common Causes:
- Extra comma creating empty slot
- Missing property name before colon
- Typo in property structure
❌ Wrong
{
"name": "John",
, // extra comma
"age": 30
}✓ Correct
{
"name": "John",
"age": 30
}SyntaxError: Unexpected string
A string appeared where it wasn't expected, usually due to missing comma.
Common Causes:
- Missing comma between properties
- Missing colon after key
❌ Wrong
{
"name": "John"
"age": 30
}✓ Correct
{
"name": "John",
"age": 30
}SyntaxError: Bad escaped character
An invalid escape sequence was found in a string.
Common Causes:
- Invalid escape like \x instead of \u
- Unescaped backslash
- Invalid unicode escape sequence
❌ Wrong
{"path": "C:\Users\name"}✓ Correct
{"path": "C:\\Users\\name"}</> XML Errors
XML Parsing Error: not well-formed
The XML document doesn't follow proper XML syntax rules.
- Missing closing tag
- Mismatched tag names
- Invalid characters in element names
- Missing root element
XML Parsing Error: mismatched tag
An opening tag doesn't match its closing tag.
- Typo in tag name
- Wrong closing tag order
- Case sensitivity (XML is case-sensitive)
XML Parsing Error: undefined entity
An entity reference (like &foo;) is not defined.
- Using HTML entities without declaration
- Unescaped & character
- Missing entity definition in DTD
--- YAML Errors
YAML Exception: bad indentation
Indentation levels are inconsistent or use tabs instead of spaces.
- Mixing tabs and spaces
- Inconsistent indentation levels
- Wrong number of spaces
YAML Exception: mapping values not allowed
A colon appeared in an unexpected location.
- Unquoted string containing colon
- Missing space after colon
- Invalid key format
YAML Exception: duplicate key
The same key appears more than once in a mapping.
- Copy-paste error
- Accidental duplicate key names
How to Triage an Error Fast
If the error includes a line or column, start there. The real mistake is often just before that point.
Words like token, brace, tag, or indentation usually point to JSON, XML, or YAML-specific issues.
If the file was working before, undo the most recent edit and re-validate. That is usually the fastest way to isolate the break.
Use JSON, XML, or YAML validation before manual debugging so syntax errors are separated from application logic.
Common Clues by Format
JSON clues
- Unexpected token or unexpected string
- Trailing comma or missing comma
- Double quotes required around keys and strings
XML clues
- Not well-formed or mismatched tag
- Unescaped ampersand or invalid entity
- Opening and closing tags must match exactly
YAML clues
- Bad indentation or mapping value errors
- Tabs instead of spaces
- Ambiguous colons, booleans, or duplicate keys
Validate Your Code
Use our free validators to find and fix errors instantly