Is HTML case sensitive?

Difficulty: 2/10

HTML syntax, case sensitivity, browser parsing

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.

Scenario Questions

0-2 years experience

2-5 years experience

1Your team is migrating a legacy page that uses uppercase tags to a modern codebase. Some CSS rules stopped applying. What could be causing this and how would you debug it?

Follow-up Questions