What is the precision of the priority field in sitemap.xml?

Question

Unfortunately the specification does not tell anything about precision. The xml scheme definition states that it is of the type xsd:decimal:

<xsd:restriction base="xsd:decimal"> 
  <xsd:minInclusive value="0.0"/> 
  <xsd:maxInclusive value="1.0"/> 
</xsd:restriction> 

I have a sitemap generator that uses up to 10 positions after decimal point. Where often only the last few positions differ. These numbers are perfectly right according to the xsd, but yet i found some pages(3,4) that state that only 0.0, 0.1, 0.2, .., 1.0 are valid values.

How will the search engines react to such a sitemap? Will some just round the value?

I know that it is unlikely that someone can provide an answer to that question, unless he works for that search engine, but i think experiences will also do.

Answer 1

I can't speak for the precision of those values as I've never used anything other than a single decimal place.

In my experience though it doesn't make much of a difference at all except that Google will try to crawl your higher priority pages first before the lower priority ones, and sometimes more frequently.

Unless you have thousands of pages on your site though, it really doesn't make any difference.

Answer 2

I'm sorry; I don't have an answer to your question. I do wonder about the sitemap generator that needs this level of precision for a concept which is pretty ethereal to begin with.

Instead of trying to share your priorities with the search engines that accurately, take the following steps:

• sort your pages in order of calculated priority
• classify them into quartiles (okay, into 11 categories, if you really, really must,)
• assign each category a priority with only one digit of precision.

I do not believe you will notice any difference in the search-engine behaviour compared to what you would see if they could understand that level of precision.

Answer 3

If you submit the sitemap to Google Webmaster Tools it should flag up any errors it encounters.

However, the level of precision you mention is ridiculous and will not have any effect. The priority is only meant to be a vague guide in the first place, and the SEs will return the page that best matches the query anyway.

I'd recommend rounding all figures to 1dp (or 2dp absolute maximum).