Below are practical, standards-aligned lists based primarily on HTML5 / HTML Living Standard usage as implemented by modern browsers. I am separating them the way developers usually need them separated in real work.
Obsolete HTML tags
Obsolete means: removed from the HTML specification and should not be used. Browsers may still render them for legacy reasons, but they are considered dead.
Fully obsolete (HTML5)
<acronym>
<applet>
<basefont>
<big>
<center>
<dir>
<font>
<frame>
<frameset>
<noframes>
<isindex>
<strike>
<tt>
Notes
<frame>/<frameset>are completely obsolete; use CSS layout or<iframe>instead.<font>,<center>,<big>,<strike>,<tt>were replaced by CSS and semantic elements.<applet>was replaced by<object>(itself rarely appropriate today).
Deprecated HTML tags
Deprecated means: still recognized, still works, but discouraged and may be removed or restricted in the future.
HTML itself has very few truly “deprecated” elements; most were moved directly to obsolete. However, the following elements are formally allowed but discouraged or contextually deprecated.
Deprecated or discouraged elements (HTML5 / WHATWG)
<menu> (traditional usage; redefined but discouraged for lists)
<menuitem> (removed from most browsers; deprecated before removal)
Historically deprecated (but now obsolete)
These are often still referred to as “deprecated” in older documentation, but are now formally obsolete:
<center>
<font>
<strike>
<tt>
<big>
Important clarification (this trips people up)
HTML5 shifted emphasis away from “deprecated tags” and instead:
- Removed elements entirely (obsolete)
- Deprecated attributes, not tags
So in modern HTML, you will see many more deprecated attributes than elements.
Common deprecated HTML attributes (for completeness)
These are still widely encountered in legacy code:
align
bgcolor
border
cellpadding
cellspacing
color
compact
height (on some elements)
width (on some elements)
nowrap
valign
All are replaced by CSS.
Practical guidance for your projects
- Treat obsolete tags as forbidden
- Treat deprecated constructs as technical debt
- Prefer semantic HTML + CSS
- Assume browsers will keep rendering obsolete tags, but validators and tools will not