HTML comments are ignored by the browser — useful for leaving notes in your markup or temporarily disabling a block of code.
Syntax
<!-- This is a comment -->
<p>This paragraph is visible.</p>Multi-Line Comments
<!--
TODO: replace this placeholder testimonial section
once the real client quotes are approved by marketing.
-->Commenting Out a Block Temporarily
<!--
<section class="promo-banner">
<p>Limited time offer!</p>
</section>
-->Useful while debugging a layout issue — hide a section without deleting the code, then remove the comment markers once you've confirmed the fix.
Important: Comments Are Not Hidden From Users
HTML comments are stripped by nothing — anyone can view them via "View Page Source." Never put sensitive information in an HTML comment (API keys, internal notes about security issues, unpublished content).
Common Mistakes
- Nesting comments —
<!-- outer <!-- inner --> still outer -->does not work as expected; the comment ends at the first--> - Leaving large blocks of commented-out dead code in production files instead of removing it via version control
- Writing sensitive or embarrassing internal notes in comments, forgetting they're publicly visible in page source
Interview Relevance
Rarely tested directly, but "are HTML comments visible to users?" is a good practical-knowledge check — many beginners assume comments are fully hidden the way server-side comments are.
Practice Question
Comment out a navigation menu item that links to a page still under construction, without deleting the code.
