A PowerPoint deck full of screenshots and photos can easily balloon past the attachment limit of most email providers. The usual culprit isn't the text or layout — it's the full-resolution images embedded in every slide, often far larger than they need to be for on-screen viewing.
A .pptx file is essentially a package of images, fonts and layout data. Photos pasted straight from a camera or screenshot tool are usually far higher resolution than a slide actually displays, so compressing just the images can shrink the whole file dramatically without touching anything else.
Your file is processed locally, never uploaded.
Text, layout, charts and slide order untouched.
Nothing leaves your device during compression.
Compression finishes in seconds for most decks.
Shrink an image-heavy .pptx deck without losing text, layout or slide order.
Compress My PPTX →This tool shines on presentations packed with photos, screenshots or scanned diagrams — the kind of deck that's often several times larger than it needs to be. Text-only presentations won't shrink much, since there's little to recompress, but any deck with embedded photos usually sees a significant size reduction.
If you're starting from a folder of photos rather than an existing deck, the same Image Compressor page can also build a PPTX for you: compress your images first, then use "Download All in PPTX" to place each one on its own widescreen slide.
Yes. Only the embedded raster images are recompressed — text boxes, charts, tables and slide transitions remain exactly as they were in the original file.
A .pptx file is a ZIP archive. Rename one to .zip, open it, and you will find the slide XML — genuinely tiny, usually a few hundred kilobytes even for a long deck — sitting alongside a media folder that accounts for almost all the weight. The text and layout are never the problem. Images, and occasionally embedded video and audio, are.
The specific culprit is that PowerPoint stores what you inserted, not what is displayed. Drag in a 12-megapixel photo from a phone, scale it down to a thumbnail in the corner of a slide, and the full 12-megapixel original is still sitting in the file. Crop it to a narrow strip and the cropped-away portion is retained too, because crops are non-destructive by design. A deck with thirty such images can run to hundreds of megabytes while displaying perhaps two megapixels of actual visible content.
A 16:9 slide is 1920 × 1080 pixels at full HD. An image that fills the entire slide therefore needs no more than about 2 megapixels for on-screen use. A quarter-slide image needs roughly 960 × 540. Anything beyond that is invisible detail costing real megabytes.
| Placement | Screen display | Projected or printed |
|---|---|---|
| Full-bleed background | 1920 × 1080 | 2560 × 1440 |
| Half slide | 960 × 1080 | 1280 × 1440 |
| Quarter panel | 960 × 540 | 1280 × 720 |
| Logo or icon | 400 px wide | 600 px wide |
PNG is lossless and correct for logos, screenshots of text, charts and anything with sharp edges or transparency. It is the wrong choice for photographs, where it can be several times larger than JPG at no visible benefit. A single 4000-pixel PNG photograph can easily exceed 10 MB where the same image as JPG at quality 85 lands under 1 MB and looks identical on a projector.
Screenshots are a common trap in the other direction: saved as JPG they develop halos around text, which looks distinctly amateur when projected. Keep screenshots as PNG and photographs as JPG, and most decks resolve themselves.
Most mail systems cap attachments at 20 to 25 MB, and base64 encoding adds roughly a third on top of the file's actual size — so a 20 MB attachment arrives as about 27 MB of message. That is why a file that looks like it should squeak under the limit gets bounced. Aim for 15 MB or below if the deck must go by email, or send a link instead.
Re-compressing images is lossy and it is not reversible. Once the deck has been through it, the original resolution is gone from that copy — so keep the master. It also cannot help with a file whose weight is genuinely video, and it will not make a badly designed deck lighter to sit through. If your slides are enormous because you pasted twelve full-page screenshots of a spreadsheet, the real fix is editorial rather than technical.
The compressor on this site opens the .pptx archive in your browser, re-encodes the embedded media and rebuilds the file locally. Slide text, layout, animations, speaker notes and structure are left untouched — only the media is re-encoded. Nothing is uploaded, which matters when the deck is a board pack, a pitch, a set of unreleased results or anything else you would not hand to an anonymous conversion service. You can verify it in the Network tab of developer tools, or by disconnecting from the internet after the page loads.
Almost certainly the images. PowerPoint stores the original file you inserted rather than the version displayed, so a phone photo scaled down to a corner thumbnail is still a full-resolution photo inside the archive. Cropped-away areas are retained too, because crops are non-destructive.
A full HD slide is 1920 x 1080, so a full-bleed image needs about 2 megapixels and a quarter-slide panel about 960 x 540. Anything beyond that is detail nobody can see, costing real file size.
No. Only the embedded media is re-encoded. Slide text, layouts, transitions, animations, speaker notes and the overall structure are left exactly as they were, and the file remains a fully editable .pptx.
PNG for logos, icons, charts, screenshots and anything with sharp edges or transparency. JPG for photographs. A large photograph saved as PNG can be several times bigger with no visible benefit, and a screenshot saved as JPG develops visible halos around text.
Attachments are base64 encoded, which adds roughly a third to the transmitted size. A 20 MB file arrives as about 27 MB of message. Aim for 15 MB or below if it must travel by email, or send a link instead.
Not from the compressed copy - image re-encoding is lossy and the discarded detail is gone. Keep your original file as the master and treat the compressed version as a distribution copy.
No. The archive is opened, re-encoded and rebuilt entirely in your browser. Nothing is transmitted or stored. Watch the Network tab in developer tools during compression, or disconnect from the internet after the page loads.