Is HTML case sensitive?

Case Sensitivity in HTML

HTML is not case sensitive when it comes to element names and attributes. For example, <H1>, <h1>, and <H1> will all be interpreted as the same heading element by the browser.

Example of Case Insensitivity

Important Notes

1
HTML tags and attributes are not case sensitive.
2
The convention is to write tags and attributes in lowercase for readability and consistency.
3
XHTML (a stricter version of HTML) is case sensitive, and requires lowercase tags and attributes.