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?

In version 2, that depends entirely on libxml2, and your charset is supported if and only if libxml2 supports it.

In Version 3.1, charset support is much expanded provided mod_xml2enc is enabled. It is normally sufficient just to load mod_xml2enc: it will be configured automatically if you configure mod_proxy_html using ProxyHTMLEnable. In a few cases, you may need to customise charset support further using mod_xml2enc's directives.

Note that some servers send inconsistent and even conflicting charset information, and may generate unexpected results. Setting ProxyHTMLMeta On may help resolve such cases, and will help diagnose problems with extra debug information in the error log.

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.

mod_proxy_html 3 supports output transformation to other charsets using ProxyHTMLCharsetOut. This requires mod_xml2enc to be loaded.

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 a markup-blind filter such as mod_line_edit, mod_substitute or mod_sed.

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

mod_proxy_html versions 1 and 2 are 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. Since everyone's requirements are different, it could not reasonably be satisfied with a simple one-size-fits-all fix. Version 3 of mod_proxy_html delegates the definition of HTML links to the system administrator, via the configuration file.

A sample file proxy_html.conf is provided, and defines standard W3C HTML/XHTML. Note that you MUST include this (or equivalent) into your configuration, or no links will be rewritten! If you need to support nonstandard HTML variants, follow the instructions in proxy_html.conf.