Best Free Image Compressor for Mac in 2025
February 2025 · 5 min read
Mac users often struggle to find a good image compressor. The built-in Preview app can export smaller files, but it offers no control over exact file size, no batch processing, and no WebP support. Here are the best options — including one that requires zero installation.
Why Mac Users Need an Image Compressor
iPhone and Mac photos in HEIC format can be 4–8MB each. When uploading to websites, email, or government forms, you need images under specific size limits — often 20KB, 50KB, 200KB, or 1MB. Mac's built-in tools do not offer this level of control.
Option 1: CompressTo20KB (Browser-Based, No Install)
CompressTo20KB runs entirely in Safari or Chrome — no download, no install. It supports HEIC files from iPhone, batch compression up to 50 images, exact KB targeting, and WebP/AVIF output. Everything runs locally in your browser, so your files never leave your Mac.
- ✅ HEIC support (native iPhone format)
- ✅ Exact KB mode (hit 20KB, 50KB, 200KB precisely)
- ✅ Batch up to 50 images
- ✅ Works in Safari on Mac and iPhone
- ✅ No install, no account, no cost
Option 2: Mac Preview (Built-in, Limited)
Preview can export images at reduced quality using File → Export → adjust Quality slider. However, it processes one image at a time, does not show the output file size before saving, and has no WebP support. It works for basic needs but lacks precision.
Option 3: ImageOptim (Desktop App)
ImageOptim is a free Mac app for lossless compression. It works well for reducing PNG sizes without quality loss. However, it does not support exact KB targeting, HEIC input, or WebP output. It is best combined with a browser tool for cases where you need a specific file size.
How to Compress HEIC Photos from iPhone on Mac
- AirDrop your HEIC photo from iPhone to Mac
- Open compressto20kb.com in Safari
- Drop the HEIC file into the upload zone
- Select your target size and output format (JPEG recommended for compatibility)
- Download and use the compressed file
Compress images on Mac — works in Safari, no install
Open CompressTo20KB →