I have a humor site that is based primarily on thumbnails and gifs. I'm in the process of converting all png's -> jpeg and gifs -> webm to save bandwidth and disk space. All in all probably about 10k images of each file type will be converted.

My questions are:

1) Can I 301 redirect to a completely different file type? png -> jpeg for example.

2) Should I expect to loose some SEO traffic?

3) What happens to my existing backlinks? My social networks have amassed a large following and I don't want my old content to be unusable.

  • 2
    "Can I 301 redirect to a completely different file type?" - A redirect is a redirect, there is no concept of "file type".
    – MrWhite
    May 23, 2015 at 11:15

2 Answers 2


Doing a 301 redirect, you should be fine. I would not try and redirect each image by name, but rather make sure that each new image has the same name, just another file extension. This should make redirecting a simple regex operation.

Having said that, I suggest using http://www.smalleranimals.com/thumb.htm especially since you have 10k images.

Here are the advantages:

  • Super fast!
  • Can run in batch mode.
  • Can replicate file names with new extensions and directory structures.
  • Super efficient. These guys are real experts and this is all they do.

But more importantly, you may not actually have to change the file type/extension. These guys are that good!!

Best of all, you can use it in trial mode for your project or pay the whopping $15 for a license! I have been using this product for over 15 years and it continues to amaze me.

I have used this on many millions of images at a time. It works great!!

  • Thanks! I actually used that tool to convert the thumbnails to JPEG as they're significantly smaller than PNGs. I ended up using ffmpeg for converting the gifs to webm. Any idea what happens to my backlinks or anyone using hotlinks to my site?
    – Kevin
    May 23, 2015 at 3:58
  • Oh yeah. I did not get into that. Sorry. You should be fine. As long as the redirects continue to work your links will not be broken and all should work just as it always has (only with a redirect). I would correct your links within your pages so that your site does not actually create a bunch of redirects though.
    – closetnoc
    May 23, 2015 at 4:16
  • Yeah, the site itself will immediately start using the new links. The only redirects will be any existing links on other domains. Thanks for your help!
    – Kevin
    May 23, 2015 at 4:18
  • 1
    Anytime my brother! We are here for you and there are some real experts on this site. Many of us are here everyday.
    – closetnoc
    May 23, 2015 at 4:20
  • "you may not actually have to change the file type/extension" - additionally, you may not need to change the "extension", even if you change the "file type". It's not really the file extension that governs the file type, providing you are sending the correct Content-Type (mime-type) header then it doesn't matter what file extension you have - although it might be a little confusing.
    – MrWhite
    May 23, 2015 at 11:13

You don't necessarily need to externally redirect.

You could keep the (URL) filename the same and either internally rewrite to the actual .jpg file, or just make sure you send the correct Content-Type header. It is, after all, the mime-type that determines the file type, not the file extension (although this might be a bit confusing).

Obviously if you don't change the filenames then nothing changes from a client's perspective. Client-side caching should be unaffected and no change to SEO.

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