Should I redirect images when I migrate my site

[ArchMedia]

We are about to migrate a large website with a fair few images (20,000). At the moment we include images in the sitemap.xml so they are indexed by Google and drive traffic (not sure how I can find out how much though).

Current image slugs are like:
http://website.com/assets/images/a2/65680/thumbnails/638x425-crop.jpg?1402460458

Like on the old site, images on the new website will also have unreadable cache slugs, like:
http://website.com/site_media/media/cache/ce/7a/ce7aeffb1e5bdfc8d4288885c52de8e3.jpg

All content pages on the new site will have the same slugs as on the old site.

Should I go through the trouble of redirecting all these images?

[LesleyPaone]

I personally would, it would be like doing have the job to not do them.

[Alex-Harford]

You can get some idea of organic image traffic if you use Google Analytics:

Acquisition > All Referrals > click on google and look at /imgres. If you want to see where the traffic is going to (to get an idea of which images) click /imgres and on the Secondary dimension dropdown go to Behaviour > Landing Page.

If it's as simple as redirecting using the same slugs (hence one global redirect rule) then I would redirect the images. If it's complicated then I might not bother, depending on whether image search leads to many visits and conversions to your site or not. Usually image traffic doesn't convert well. If you're migrating to a new domain and keeping the same folder structure it should be as easy as doing one global redirect?

Rather than redirecting I'd most likely take the opportunity to make the filenames of images more friendly than ce7aeffb1e5bdfc8d4288885c52de8e3.jpg by using short descriptive filenames.

[David-Kley]

Take a look at the image index rate, and see how many are indexed and showing. 20k images is quite a bit, and I would want to see if Google actually indexed them all before I started creating redirects for that many items.

If they are indexed, see if there is a way on your new site's sytem to have the images named the same. That way you would only be creating a redirect for the image paths, and not the images themselves. Example:

oldsite.com/image/25/coolpicture.jpg
newsite.com/images/awesome/25/coolpicture.jpg

All that would be needed would be an HTACCESS rule redirecting from one directory to the other, using the image name as a variable. You could probably redirect most of them using only a few rules than 20,000 separate redirects.

Is it worth it to redirect? I think that depends on how many are indexed, and if the images bring you a significant amount of traffic.