A slide deck’s size almost always comes down to two things: image resolution and embedded media. Unlike a Word document, PowerPoint gives you a built-in tool aimed squarely at the first one — worth using before reaching for anything else. If you’d rather skip PowerPoint entirely, Compress PowerPoint does the same image re-encoding automatically: upload the .ppt or .pptx and download a smaller version in seconds, with your slides, animations, and layout untouched.
Every image pasted into a deck is typically stored at whatever resolution it was when you inserted it, often much higher than a slide actually needs. PowerPoint can re-encode all of them at once: click any image → Picture Format → Compress Pictures, choose a target resolution (Screen, 150 ppi, is usually plenty for a presentation shown on a projector or screen — nobody is examining a slide photo at print resolution), and check “Apply to all pictures in this file” so you only do this once. This alone often cuts a photo-heavy deck’s size by more than half with no visible quality loss on screen.
Beyond images, three things are worth removing outright: hidden slides you’re not using anymore (a hidden slide is excluded from the show but still fully present in the file, images and all), a bloated master or unused layouts (decks that started life as a copy of another presentation sometimes carry slide layouts and theme assets nobody in the current deck actually uses), and speaker notes you don’t need to keep, especially any that reference now-removed content or contain pasted screenshots of their own.
Video is the other big one, and often the biggest — an embedded video, especially recorded at high resolution, can dwarf every image in the deck combined. If you don’t need it embedded, link to it instead (from cloud storage or a shared drive) if the deck will always be presented in a context where that link resolves, compress the video separately before inserting it at a resolution matched to how it’ll actually be shown, or trim it to just the portion you use rather than embedding a full-length source clip. If a single embedded video is the reason the deck is enormous, compression alone will not get you far — How to Shrink a PowerPoint With an Embedded Video covers the options for that case specifically.
If the deck’s destination is someone reading or presenting from it rather than editing the slides, converting to PDF sidesteps the whole problem: PowerPoint to PDF turns the presentation into a single, much smaller file that opens on any device without PowerPoint installed, and animations aside, looks identical to the original. If it’s still too big afterward — unusual once it’s a PDF, but possible with a very image-dense deck — Compress PDF shrinks it further.
Related reading: Why Your PowerPoint Looks Wrong on the Presentation Laptop is a different problem with the same underlying fix — bring a PDF as backup — and How to Reuse a Deck When All You Have Is the PDF covers recovering editable slides from a PDF, the reverse direction.
Shrink the deck with the free Compress PowerPoint tool — or, for sending rather than editing, PowerPoint to PDF works the same way. No sign-up, no watermark, nothing stored.