Compress Images for PowerPoint — Free, Fast & Private
A .pptx is a ZIP archive. Rename one and look inside: nearly all of its weight sits in ppt/media/, the folder holding every image you ever pasted in. Text, layout and animation are kilobytes. A 90 MB deck is 89 MB of photographs.
That matters because PowerPoint stores what you gave it. Drag in a 12 MP phone photo, scale it down to a corner of the slide, and the full 12 MP original is still in the file — the resizing is display-only. Do that twenty times and the deck will not fit through email.
1920px is the ceiling that actually matters
A 16:9 slide is 13.333 × 7.5 inches. Projected or shown full-screen, it maps to 1920 × 1080 on almost every display in use — conference room projectors are frequently 1280 × 800 and worse. An image wider than 1920 px cannot show you extra detail on that surface; the pixels are discarded at render time. You are carrying them for nothing.
So the sizing rule is simple: full-bleed background image, 1920px. Half-slide image, 960px. Quarter-slide or logo, 480px. Match the pixel width to the fraction of the slide the image occupies. This single habit does more than any compression setting.
Why compress before inserting, not after
PowerPoint has its own compressor — Picture Format → Compress Pictures, offering presets around 96 ppi for email, 150 ppi for web and 220 ppi for print. It works, but it has two drawbacks. It is applied late, after the bloated file already exists and has been saved and synced a few times. And it is coarse: one setting for every image in the deck, whether that image is a full-bleed photograph or a screenshot of a chart.
Compressing first gives you per-image control. A photograph tolerates JPEG at the Smart preset with no visible difference on a projector. A screenshot of text or a chart does not — JPEG smears the edges of small type into grey mush, and that is the one thing an audience will notice. Keep screenshots as PNG, and shrink them by width rather than by quality.
If the deck still will not send
Corporate mail gateways commonly refuse attachments in the 10–25 MB range, and the limit is enforced on the encoded size, which is roughly a third larger than the file on disk. A 20 MB deck can be bounced by a 25 MB limit for that reason alone.
Check what is left after compression: embedded video (compression here does not touch it), and the slide master — a background image on the master is stored once but rendered on every slide, and a heavyweight one is easy to forget about because it never appears in the slide sorter.
MiniPx compresses in your browser, so an unreleased deck of internal figures never leaves your machine. Drop the whole folder of images in at once, set the width, and export them together.
Related: the same deck in Google Slides · pasting those screenshots into Notion