The Vary HTTP Header

When developing mobile websites, responsive or adaptive, there are some important factors to consider outside of the IA involved with UI and design. An important consideration is whether you’ll be serving the website using the same URL for both desktop and mobile websites, and the order of content between the two sites. A responsive mobile site involves the same HTML being served regardless of device, however using the adaptive technique has a high chance the HTML will differ.

When serving the mobile website on the same URL, modifying the HTTP Headers is recommended to hint the Googlebot-Mobile should crawl the page too. Not only so it discovers your content faster, but it also helps discover content as mobile content while not immediately apparent that the site alters the HTML for mobile user agents. Additionally, it signals to caching servers that they should consider this user agent when deciding to serve the page from cache or not.

So, what does the Vary HTTP header look like?

Ta da!