HTML Writing HTML for the Web (comp.infosystems.www.authoring.html)

Discuss length of html attribute in the HTML forum.


I did not find any length limit for attributes. Is there any? Maybe
“inherited” by SGML?

Best Regards,


The SGML declaration (
declares a maximum length of 65536 characters, which is the largest value
that SGML allows and which comes closest to the ‘intended limit’ of ‘no
If you write a HTML parser, do not implement size limitations. If you are
authoring HTML code, you’ll win a prize, if you manage to exceed the 64k
limit with meaningful data…

Benjamin Niemann wrote:

Been there, done that.

For metadata embedding, it’s (reasonably) common practice to embed
annotations and descriptions as attributes that are lifted from a
Dublin Core (or similar) “pseudo-namespace”. These aren’t part of valid
HTML, but XML namespacing isn’t really available to the web yet and
it’s long-established web practice that extra attributes are silently
and safely ignored by user-agents that don’t understand them.

Once you’re adding annotation or metadata, it’s not hard to start
breaking 64k length limits, if you’re unaware of the issue.