Powerpoint File Size Does Not Reduce Even After Deleting Slides

Updated 10 Jul 2018 - After some testing, I find that those "extra" template slides appear when you try to copy some slides and paste them to another deck with "Keep Source Formatting". So if you frequently encounter this problem, you could be like me, often having to take content from different decks and piece together a customized deck for the work on hand. If so, then the solution below should help with your Powerpoint file size.

If you work with Powerpoint slides a lot, you may have seen some pretty big and bloated slide decks, especially if it contains lots of photos or video content. This presents an issue when sending over email with attachment size limits. Most of the time, deleting slides or compressing content should help to reduce the size. 

If you had come upon this article after googling, you probably had just encountered a similar frustrating experience as me. Even after removing most of the content, the Powerpoint file size remains mostly the same. Most online posts revolve around talking about how to compress the ppt files or simply just deleting unnecessary content. Not many discuss why certain ppt decks remain stubbornly big even after deleting content. The only closest I could find was this Microsoft Community post which did not help much.

A simple workaround I found to reduce Powerpoint file size was to copy the slides into a new ppt and save the new file. Beware that even though I had Copy and Paste with "Keep Source Formatting", sometimes I would still encounter funny results, for example, shape sizes becoming distorted. So do check through your final slides before sending them out or using them for presentation.

Back to the topic on hand, it did not make sense that the Powerpoint deck would not become smaller after deleting stuff. So I did a little further test by deleting all the slides from the original slide deck and saving the file with another name. The file size of this "empty" ppt deck was roughly the size that was reduced, had I copied the slides to a new file.

So it became apparent that this "empty" file was not the problem. It was then that I realized where the issue was. As this was a corporate presentation slide deck, it came with a corporate theme. It was not immediately apparent but all the years of copy-and-paste by various authors had injected junk templates from other sources into the theme over the years of use. You would see these templates if you right-click on a slide to see the layout types available.

To rectify, go to View > Slide Master. This will show all the slide templates stored in this theme. For my case, I saw a lot of junk templates unrelated to the theme. Once I removed those that I did not want and save, the file immediately became a manageable size.

I guess that for convenience, people just kept reusing the base file by deleting all previous slides and start adding their slides. I still cannot fathom why those content would go into the base theme template, but next time you encounter big Powerpoint files that just would not become smaller, try looking at the theme first.


  1. I have encountered this problem and in my case it does not appear to be as simple as junk in the master templates (though I think that's part of it -- read on to hear the weirdness!).

    I have a 1 page presentation. In the master, there a footer with a logo that when saved as a .png by itself, is 12K. There are also the default templates under the master that PowerPoint creates for all files. But, they have not been edited. All they do is inherit from the master.

    There are NO graphics (other than the logo inherited from the template. There are just some tables on my single page.

    This did not start as a 1 page presentation. I deleted several other pages to see how much the file size went down when I deleted the other pages.

    The file size of the single page version was 3.5MB, down from 3.8MB after I deleted all the other slides (that did have some graphics). That 0.3MB reduction seems reasonable, but where is all that 3.5MB coming from when I have maybe 100K of content?

    I then deleted the tables to make sure that their definition wasn't huge for some reason. It reduced the file size by 10K (3,560KB to 3,550KB). Then I removed everything, so I had essentially a blank slide with only what was specified by the master. That reduced it by 4K to 3,546KB.

    OK, so at this point it seems like the bloat is in the master, or it's hidden as obsolete junk.

    To test which it was, I went into the slide master view and I deleted all the templates that were not needed (leaving only the master and one sub-template).

    After deleting the unused templates WHICH HAD NOTHING ON THEM EXCEPT THAT WHICH THEY INHERITED FROM THE MASTER (they were just the default layouts that all PowerPoint presentations start with), the file size dropped to 185K!

    OK, that's a reasonable file size. But how I got down to 185K doesn't make any sense, because there was nothing on those unused templates that were deleted.

    So, assuming that removing the unused templates fixes the problem I went back to a file with the text and tables (which we know only saved 10K to delete before). Then I deleted the unused templates from that, assuming I would end up with a files just slightly larger than the 185K due to the tables being there.

    The file size was 3,551KB. What?

    Then, just to see what would happen, I deleted the tables again (in a file where the unused templates had already been removed). In other words, I was going to end up with a blank page (except for the small master graphic logo) with no unused templates, and no content on its single page. We already know what that file size should be: 185K.

    It was 3,539K. Again, what?

    That implies that order of operation matters: Deleting the tables first and then deleting the unused templates = 185K file. Deleting the unused templates first and then the tables = 3,939K file.

    Next, I deleted ALL content, both on the single page and on the 2 template files (the master and the one sub-template). So, I had a completely blank master and sub-template. COMPLETELY blank. I didn't even leave empty boxes. The master and template were just a white background. The single page was just a white background.

    The file size was 2,375MB.

    At this point I through up my hands in disgust. I'm just reporting this in case it is helpful to someone who knows more than I.

    Despite the skepticism I see in some answers, there is clearly a problem with PowerPoint bloat, since a completely empty file can be over 2MB. And, given that at least in some cases order of operation matters, that's a bug, plain and simple.

    This was done using a Microsoft 365 Apps for enterprise subscription. PowerPoint was version 2104 (Build 13929.20296 Click-to-Run), with all updates installed.

    1. Hey james, wow thanks for sharing your tests and observations. You are right, it can be challenging to reduce Powerpoint files. I would definitely try out your steps and see if I can get similar observations.

      Meanwhile, another thing I have observed is to use 'Inspect Presentation' option (File > Info > Check For Issues) to check for any junk like off-screen objects or hidden on-screen objects. There may also be macros that would get picked up. Maybe you can try running 'Inspect Presentation' to identify any bloat coming from these.

      Personally, before sending any slides, I would always run 'Inspect Presentation' to remove all notes in case there are any sensitive information. The other items mentioned above are default selected areas to check as well. Highly recommend everyone to do this hygiene step as well.


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