A 20-slide deck has maybe 30 photos in it. Drop in phone photos at 4000 px each and the file passes 80 MB — too big for most email limits and painfully slow to open. Text and shapes contribute almost nothing; the images are the file.

The Right Pixel Widths

Nothing benefits from being larger than the surface it's displayed on:

  • Full-bleed slide image (16:9 deck): 1920 × 1080 px is plenty. A 4K projector still renders a 1920 px image cleanly, and slides are viewed from a distance.
  • Half-slide or inset image: 960–1280 px wide.
  • Word document, full text width (A4): ~1600 px wide covers printing at 200 DPI; 1200 px is fine for screen-only documents.
  • Inline logos and icons: 300–600 px, or a vector if the app supports it.

Anything beyond those numbers is invisible detail carried at full weight in every copy of the file you send.

Two Ways to Fix It

Before inserting (best): batch-resize the photos to the target width and compress them to a sensible weight (200–400 KB each for full-slide images), then insert. The document stays small from the start, and you keep clean originals separately. A browser-based batch tool with one setting applied to the whole folder is the fast path here.

After the fact: both Office apps have a built-in *Compress Pictures* option (select an image → Picture Format → Compress Pictures) with presets like 150 ppi. It works, but it re-compresses whatever is already embedded — including images that were already lossy — so quality erodes more than pre-sizing does. Also worth doing: *File → Info → Compress media* for embedded video, and re-saving after deleting cropped-away areas, since Office often keeps the discarded pixels.

Format Choices Inside Documents

  • Photographs → JPEG. Quality 80–85 is undetectable on a projector.
  • Screenshots, charts, diagrams → PNG. Text and sharp lines get mangled by JPEG; PNG keeps them crisp. If a screenshot is huge, crop it to the relevant region rather than switching it to JPEG.
  • Transparent logos → PNG (or WebP if your Office version supports it).
  • Avoid pasting screenshots directly from the clipboard repeatedly — it's easy to embed the same large bitmap many times.

One Habit That Prevents the Problem

Keep a "for-deck" copy of your images: crop → resize to 1920 px → batch compress, all in one pass, before the deck is built. It takes a minute for a whole folder, keeps the file under email limits, and means nobody ever waits 30 seconds for your slides to open.