HTML5 validator failing on Facebook OpenGraph XML Namespace xmlns:og

HTML 5 validator is failing on my code despite me following the Facebook documentation to the letter. There are a variety of problems but let's start with one example to start with.

I'm following the Facebook "Getting Started" documentation and using th5is code:

<html xmlns=""

The only difference is I precede this with <!DOCTYPE html> for HTML5. When running it through the W3C HTML5 validator I get this error:

 Attribute xmlns:og not allowed here

The only things I can think of what the error are:

  1. Facebook's documentation is wrong
  2. I'm supposed to add some kind of namespace to the <!DOCTYPE html> declaration.

However, in either case I don't know what the fix is. Would love some help!


fb's documentation isn't wrong, but their approach to open web is. those are fb proprietary attribute values, so they're not going to ever validate, unless w3c makes them standards. that may sound gloomy, but as long as those are your only validation errors, don't worry about it. validation is an awesome tool, but remember, it's just a tool.

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