Im trying out a new image serving solution that serves responsive images. It does so by detecting the img tag elements width and then serving a version of the image that is suitable for that size.

It does so by changing the source of the image from :




Note : How it adds a query string at the end of the URL (in the above example the second version of the image would be served at 1400px wide were as the first one would be the unscaled version)

My question is how the query string at the end of the image url would effect SEO, the alt tag is going to be the same (as its the same image, just at different sizes) would the fact that the image url changes (although the base URl dosnt change(just a query string is added)) effect SEO negatively by making google think that there were several versions of this image or infact they were different images all together ?

  • How are you detecting the width and serving the different image? Hasn't the image already loaded by the time you check its width? Sep 6, 2015 at 16:10
  • @DisgruntledGoat - the image width that is served is based off the img elements width which is usually 100% of its parent div
    – sam
    Sep 6, 2015 at 17:54
  • I mean, how are you actually detecting that? Using JavaScript? Still not seeing how you can figure out the width before the original image loads. Sep 6, 2015 at 22:20
  • Yeah its with JS - the service is called imgix.com and the js library is called imgix.js - imgix.com/imgix-js
    – sam
    Sep 7, 2015 at 8:36

1 Answer 1


Using Google Webmaster Tools 'Fetch as Google' function you'll be able to see the page as the Googlebot see's it.

You'll note it's only the source code that the bot see's - not the actual rendered DOM.

If you're checking element widths with JS and changing the image source client side, Google will only see the original URL.

  • 1
    Ive been reading up some more and in addition to the above Google does crawl JS, although wont show the rendered DOM in WMT. But you can tell google to ignore select part or all of the query string using the URL parameters tool in WMT
    – sam
    Sep 6, 2015 at 17:55

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