HTML Syntax Compatibility

Expressions must be HTML compliant because they are parsed as HTML. The < character in a text node expression would be interpreted as the opening of an HTML tag, causing a parsing error. However, < is allowed in attribute expressions when properly quoted. This applies to all characters that carry a special meaning in HTML. Caution against being too clever, and thorough testing, is recommended.

• Text nodes: Use {bar > foo} instead of {foo < bar}
• Text nodes: Use {bar >= foo} instead of {foo <= bar}
• Attributes: < character works when expressions are quoted in attributes, but doesn’t work in text nodes
• Both: Avoid expressions that contain < followed by text that could be interpreted as HTML tags

Complex template expressions in attributes must be quoted. This requirement is backward compatible with existing LWC templates — simple property bindings don’t require quotes.

• Complex expressions: Must be quoted (any expression with operators, function calls, etc.)
• Simple property bindings: Don't need quotes (just property names like {value})
• Backward compatibility: Existing simple bindings continue to work without quotes

HTML entities are not decoded in expressions:

Certain expressions can cause HTML parsing issues when they contain characters that have special meaning in HTML:

Avoid expressions that:

• Contain < followed by text that could be interpreted as an HTML tag
• Contain </ followed by text that could be interpreted as a closing HTML tag
• Mix HTML-like syntax within string literals