What is Image Compression? How It Reduces File Size

Image compression makes image files smaller so they take less storage space and transfer faster. There are two types.

Lossy Compression

Removes some image data permanently. JPEG uses lossy compression. At moderate quality levels (60-80%), the difference is barely visible to the human eye, but the file size drops significantly. At very low quality levels, you start seeing blocky artifacts. This is irreversible: you cannot recover the original quality from a compressed JPEG.

Lossless Compression

Keeps all image data intact. PNG uses lossless compression. The file can be perfectly reconstructed. File sizes are larger than lossy equivalents, but quality is preserved exactly. Best for images with text, screenshots, logos, or graphics where every pixel matters.

Why It Matters for Presentations

PowerPoint files often contain high-resolution photos that were never resized for the slide dimensions. A 4000x3000 photo in a slide that only displays at 1000x750 wastes space. Compressing these images can reduce a 50 MB presentation to 15 MB without visible quality loss.

How SaveSlide Handles Compression

The PPTX Image Compressor finds JPEG and PNG images inside your PPTX file and compresses them at a quality level you choose. It runs in your browser, so your file never leaves your device. The tool shows exact before/after file sizes so you can see the real savings.