Is FastCompressor safe?
Yes. Completely. Here's why you see that warning — and how to fix it.
FastCompressor is a legitimate offline image and video compression tool used by thousands of designers, developers, and content creators. The security warning you see comes from Windows or macOS — not from anything wrong with the app.
Why does my computer say this?
Windows protected your PC
Microsoft SmartScreen flags any app that doesn't have a Microsoft Authenticode code-signing certificate. This certificate costs ~$400/year and requires business verification. The warning has nothing to do with whether an app is safe or unsafe — itonly means the developer hasn't purchased that certificate yet. Even perfectly clean apps get this warning until they do.
Apple cannot verify this app
Apple Gatekeeper blocks apps from developers not enrolled in Apple's $99/yearDeveloper Program or who haven't completed Apple's notarization process (where Apple scans the app for malware and issues a certificate). We are actively completing this process. Until then, macOS will block the app on first open — but you can easily allow it in one extra step.
What we're doing about it
App built, tested, and distributed directly — zero malware, zero network requests during compression
Apple Developer Program enrollment — in progress. Notarization removes the macOS Gatekeeper warning entirely.
Microsoft Authenticode code signing certificate — in progress. Removes the Windows SmartScreen warning.
Microsoft Store listing — live. Use the Store download for the smoothest Windows install and updates.
Mac App Store submission — planned after notarization. Will allow one-click installation with no warnings.
How to open FastCompressor right now
Follow the steps for your operating system below. Each takes less than 30 seconds.
You may see a security warning
100% SafeBecause this is a direct download and not from the App Store, your computer might show a standard "unrecognized app" prompt. Here is how to safely bypass it in seconds.
Run the installer (.exe) to see the blue SmartScreen dialog.
Click "More info" (the small text link below the warning).
A "Run anyway" button will appear at the bottom.
Click it, and the installer will proceed normally.
Need complete peace of mind? You can also download FastCompressor directly from the verified Microsoft Store.
Move the downloaded app into your Applications folder.
Right-click (or Control-click) on the app icon.
Select "Open" from the context menu.
Click "Open" in the security dialog that appears.
The app opens and the warning won't appear again.
Download the .AppImage file to your computer.
Open a terminal in the folder where it was downloaded.
chmod +x FastCompressor-*.AppImage./FastCompressor-*.AppImageWhy you can trust FastCompressor
Zero network calls
The app processes every file locally. It makes no outbound requests while compressing.
Files stay with you
Nothing is uploaded to any server. You can run FastCompressor in airplane mode.
Real support
FastCompressor is a real product with a real support email and a help center.
Still have questions?
We're a small team and we respond to every email personally. Reach out if you need help getting started.