How to compress PNG files on a Mac

PNGs are lossless, which keeps them crisp — and large. Screenshots and UI exports are often 5–10× bigger than they need to be. Here are three ways to shrink them on macOS, from built-in to best.

1. Preview (built in, limited for PNG)

Open the PNG in Preview, then File → Export…. For JPEG or HEIC output you get a quality slider, but for PNG there's no compression control — Preview just re-saves the file, so it often barely shrinks (or even grows). Preview is mainly useful when you also want to resize: Tools → Adjust Size…, since fewer pixels always means fewer bytes.

2. Finder's Convert Image Quick Action

Right-click a PNG in Finder → Quick Actions → Convert Image. You can convert to JPEG or HEIF and pick a rough output size. It's handy in a pinch, but you lose transparency, you can't control quality precisely, and results vary.

3. TinyPresso (the big win)

Here's the trick that actually makes PNGs dramatically smaller — the one TinyPNG made famous: a PNG stores far more shades of color than your eyes can tell apart. Throw away the invisible extras, keep everything you actually see, and the file routinely gets 60–80% smaller while looking identical.

TinyPresso does this natively on your Mac: drag PNGs in (or paste with ⌘V), press Compress, and compressed copies land in your export folder. In our benchmarks a 2.3 MB photo-heavy PNG dropped to 734 KB, and flat-color images compressed by more than 80%. It's free, works in batches with no size limits, and never uploads anything — unlike web tools.

Tips for the smallest PNGs

• Resize first. A 5K screenshot shown at 800px wide carries wasted pixels no compressor can save you from.
• Keep PNG for UI, screenshots and transparency. For photos, JPEG/HEIC/WebP are usually smaller — TinyPresso can convert in the same drop.
• Don't recompress the compressed. Good tools (TinyPresso included) simply keep the original when no savings are possible.