Download FastCompressor
for Mac
FastCompressor is a lightweight desktop app for Mac that helps you reduce image sizes instantly with no internet needed.
macOS may block it on first open — follow the 30-second fix
No admin rights required
Install nicely without password.
Works offline
100% local processing.
Free tier included
Compress unlimited images.
Universal Binary
Native for Intel & Apple Silicon.
You may see a security warning — here's why it's safe to ignore
FastCompressor is a legitimate app. Store installs avoid these warnings when available. Direct installers can still show a warning because they are distributed outside the Mac App Store or Microsoft Store. Here's exactly what to do.
macOS Gatekeeper blocks apps from developers who haven't paid for Apple's $99/year Developer Program and gone through their notarization process. We're enrolled and actively completing this. Until then, here's the two-step workaround:
Open the downloaded .dmg and drag FastCompressor to your Applications folder
Try to open FastCompressor from Applications — macOS will block it
Go to System Settings → Privacy & Security → scroll down
You'll see "FastCompressor was blocked" with an "Open Anyway" button — click it
Enter your Mac password if prompted, then click "Open" in the final dialog
Alternative: right-click method (older macOS)
1. Find FastCompressor in your Applications folder
2. Right-click (or Control-click) on the app icon
3. Select "Open" from the context menu
4. Click "Open" in the security dialog that appears
5. The app opens and the warning won't appear again
Need help installing? Visit FAQ