How to Compress a Pitch Deck (PPTX) for Email and Investor Portals

Why upload limits catch founders out

You finish the deck at midnight, open the accelerator application or the investor's data room, and the upload button says the file is too large. It is a common moment. Many application forms, CRM-linked portals and email providers cap attachments, and the limits are often somewhere in the 10 to 25 MB range. They vary a lot, though, and change over time, so always check the exact number on the portal you are using rather than relying on a figure you remember.

The good news is that a pitch deck rarely needs to be large. Twelve to twenty slides of text, charts and a handful of photos can almost always fit comfortably under typical limits. When a deck balloons to 40, 80 or 150 MB, there is usually one specific reason, and once you know it the fix takes a couple of minutes.

What actually makes a PowerPoint file big

A .pptx file is really a ZIP package. Inside it are XML files for each slide, layout and theme, plus a media folder holding every picture, video and audio clip. Text and shapes take up very little space. The media folder is where the weight lives.

• Full-resolution photos. A product photo straight from a phone or a stock site can be several thousand pixels wide. PowerPoint stores the original even when you shrink it to a thumbnail on the slide.
• Screenshots saved as PNG. PNG is ideal for crisp interface shots, but a full-screen PNG of a dashboard can be surprisingly heavy, and you may have pasted the same screenshot several times.
• Embedded video. A thirty-second product demo dropped onto a slide can outweigh the rest of the deck many times over.
• Cropped images. Cropping in PowerPoint hides part of the picture but often keeps the full original in the file.
• Unused layouts and leftover media. Decks built from a purchased template or copied from an older version often carry slide masters, layouts and pictures that no slide uses any more.

TipTo see what is heavy, make a copy of the deck, rename it from .pptx to .zip and open it. The ppt/media folder lists every picture and video with its size. Do not edit the renamed copy; just look.

Compress the deck without changing your slides

Compress PowerPoint (PPTX) works on that media folder and leaves everything else alone. It downsamples oversized pictures to a sensible resolution for screen viewing, re-encodes them, converts opaque PNGs (ones with no transparent areas) to JPEG and updates the slide references so nothing breaks, removes media files that no slide references, and repacks the whole package at maximum ZIP compression.

Your text, slide layouts, animations, transitions, charts and speaker notes are not touched. Logos and icons with transparent backgrounds stay as PNG so they do not pick up a white box. Embedded videos are kept as they are, so if a video is the main source of weight you will need to deal with it separately (see below).

Everything runs in your browser. The deck is not uploaded to a server, which matters when it contains your cap table, revenue figures or an unannounced product. You can also drop in several decks at once, for example the full deck, a short teaser and an appendix.

When compression alone is not enough

If the file is still over the limit after the Strong level, look at what remains. Almost always it is video.

• Move the demo video to a link. Upload it to your usual video host or shared drive and put a clear 'Watch the 60-second demo' link on the slide, with a still frame as the image. Investors who want to watch will click.
• Delete hidden and backup slides. Hidden slides still carry their pictures. If they are not for this audience, remove them from this copy.
• Replace giant screenshots. If one screenshot is the whole problem, crop it to the part that matters before inserting it again.
• Send a PDF instead. A PDF export drops video and animation, and is often much smaller. Use PowerPoint to PDF, then Compress PDF or Target-size PDF if the portal gives you an exact number to hit.

Watch outDo not compress the only copy of your deck. Keep the original master with full-quality images for future edits and printing, and treat the compressed file as a version for sending.

PPTX or PDF for the upload?

Read the portal's instructions first. Some ask specifically for PDF, some accept either. When you have a choice, think about who opens it and how.

For a first send to an investor or an accelerator, a PDF is usually the safer default because it looks exactly as you designed it. Keep the PPTX for when someone asks to present it or reuse slides. We go deeper into this choice in Should you send your pitch deck as PDF or PPTX? and cover the export itself in PowerPoint to PDF without losing your slides.

Check the result before you hit send

1. Open the compressed file in PowerPoint (or whichever app the recipient is likely to use) and click through every slide.
2. Zoom in on photos of people, product shots and any small text inside screenshots. If something looks soft, rerun that deck on Light.
3. Play any animations you rely on to make the story land.
4. Check the file size in your file manager against the stated limit, leaving a little headroom.
5. Rename the file clearly, for example CompanyName_Seed_Deck_Oct2026.pptx, so it is easy to find in an inbox.

If you are emailing rather than uploading, our guide to sending a PDF that is too large for email covers attachment limits and sharing links in more detail.