Be honest with yourself about what’s actually making a deck enormous before reaching for a compressor: if it’s one 40 MB training clip embedded on slide 12, no amount of squeezing the photos on the other 49 slides is going to move the needle much. Video and images are different kinds of content, and they need different fixes.
Compress PowerPoint re-encodes embedded images — photos, screenshots, logos — to a smaller, screen-appropriate size, and that’s genuinely effective for a photo-heavy deck. It doesn’t re-encode embedded video, deliberately: video compression is a different kind of processing (re-encoding frames over time, not resizing a single image), and doing it well requires choosing quality and format tradeoffs specific to the footage, not a one-size setting applied automatically. If a deck is large mainly because of video, running it through an image compressor will shrink the photos and barely move the total.
What actually shrinks a video-heavy deck is handled inside PowerPoint itself. Compress the video before or after embedding it, using PowerPoint’s own built-in tool: go to File → Info → Compress Media and pick a target quality — “Internet Quality” or “Low Quality” for a deck that’s mainly going to be viewed on a screen, not projected at full resolution. This re-encodes every embedded video and audio clip in the presentation in place, often cutting a video-heavy deck’s size by more than half with no re-recording needed. Trim what doesn’t need to be there, too — PowerPoint’s Playback → Trim Video cuts the clip down to the segment you actually show, and the file size drops proportionally, so a 10-minute source clip trimmed to the 90 seconds actually used in the presentation is a fraction of the size. Link instead of embed, if the deck will always be presented from the same machine or a shared drive — Insert → Video → the “link to file” option keeps the presentation itself small and points to the video file separately, rather than baking a full copy into the .pptx, though this only works if the video file travels alongside the deck or lives somewhere accessible from wherever it’s presented, and it breaks if you email just the .pptx and the video isn’t attached too. And re-export the source video at a lower resolution before inserting it at all, if you have the original file and it was recorded at 4K or another resolution far higher than a projector or laptop screen will show anyway — 1080p is plenty for virtually every presentation context.
Once the video is handled, if the deck also has a lot of full-resolution photos, Compress PowerPoint is exactly the right tool for that half of the problem — upload the file after you’ve compressed or trimmed the video, and it shrinks every embedded image automatically, with your slides, animations, and layout otherwise untouched.
After you’ve done both: convert the finished deck to PDF for circulating a reference copy, since a PDF strips video and animations entirely (they don’t survive PDF export regardless), so it will be dramatically smaller than the .pptx if the recipient just needs to read the slides; and compress the PDF further if it’s still too large for email after that.
Related reading: How to Compress a PowerPoint Presentation and Why Your PowerPoint Looks Wrong on the Presentation Laptop.
Once the video is sorted, the free Compress PowerPoint tool handles the rest of the deck — nothing to register for, no watermark, file discarded once you’re done.