mod_proxy_html: Frequently Asked Questions

This answers some of the most frequently asked questions that aren't dealt with (or that people overlook) in the documentation and the apachetutor tutorial. This was written for Version 2, and most of the questions are moot in Version 3.


  1. Can mod_proxy_html support (charset XYZ) as input?
  2. Can mod_proxy_html support (charset XYZ) as output?
  3. Why does mod_proxy_html mangle my Javascript?
  4. Why doesn't mod_proxy_html rewrite urls in [some attribute]?


Can mod_proxy_html support (charset XYZ) as input?

That depends entirely on libxml2. mod_proxy_html supports charset detection, but does not itself support any charsets. It works by passing the charset detected to libxml2 when it sets up the parser.

This means that mod_proxy_html inherits its charset support from libxml2, and will always support exactly the same charsets available in the version of libxml2 you have installed. So bug the libxml2 folks, not us!

In Version 3, charset support is much expanded provided ProxyHTMLMeta is enabled, and any charset can be supported by aliasing it with ProxyHTMLCharsetAlias.

Can mod_proxy_html support (charset XYZ) as output?

libxml2 uses utf-8 internally for everything. Generating output with another charset is therefore an additional overhead, and the decision was taken to exclude any such capability from mod_proxy_html. There is an easy workaround: you can transcode the output using another filter, such as mod_charset_lite.

Version 3 supports output transformation to other charsets using ProxyHTMLCharsetOut.

Why does mod_proxy_html mangle my Javascript?

It doesn't. Your javascript is simply too badly malformed, and libxml2's error correction isn't what you expect! Check it with a validator, or with libxml2's xmllint --html (which uses the same parser as mod_proxy_html). Here is a fuller explanation.

The best fix for this is to remove the javascript from your markup, and import it from a separate .js file. If you have an irredeemably broken publishing system, you may have to upgrade to mod_publisher or resort to the non-markup-aware mod_line_edit.

Why doesn't mod_proxy_html rewrite urls in [some attribute]?

mod_proxy_html is based on W3C HTML 4.01 and XHTML 1.0 (which are identical in terms of elements and attributes). It supports all links defined in W3C HTML, even those that have been deprecated since 1997. But it does NOT support proprietary pseudo-HTML "extensions" that have never been part of any published HTML standard. Of course, it's trivial to add them to the source.

This has been the most commonly requested feature since mod_proxy_html 2.0 was released in 2004. It cannot reasonably be satisfied, because everyone's pet "extensions" are different. Version 3 deals with this by taking all HTML knowledge out of the code and loading it from httpd.conf instead, so admins can meet their own needs without recompiling.