Why are HTML character entities necessary?

Question

Why are HTML character entities necessary? What good are they? I don\'t see the point.

Answer 1

In SGML and XML they aren't just for characters. They are generic inclusion mechanism, and their use for special characters is just one of many cases.

Regards, &myname;
">

This kind of entities is not useful for web sites, because they work only in XML mode, and you can't use external DTD file without enabling "validating" parsing mode in browser configuration.

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Entities can be expanded recursively. This allows use of XML for Denial of Serice attack called "Billion Laughs Attack".

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Firefox uses entities internally (in XUL and such) for internationalization and brand-independent messages (to make life easier for Flock and IceWeasel):

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In HTML you just need <, & and " to avoid ambiguities between text and markup.

All other entities are basically obsoleted by Unicode encodings and remain only as covenience (but a good text editor should have macros/snippets that can replace them).

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In XHTML all entities except the basic few are problematic, because won't work with stand-alone XML parsers (e.g.   won't work).

To parse all XHTML entities you need validating XML parser (option's usually called "resolve externals") which is slower and needs DTD Catalog set up. If you ignore or screw up your DTD Catalog, you'll be participating in DDoS of W3C servers.