FB2Combiner

Listen, yesterday I went down a little rabbit hole with FB2Combiner (app) and figured I’d share, because it was one of those “this should take five minutes” things that turned into an hour of poking around macOS security.

The short version: it wouldn’t open. Classic macOS message — “FB2Combiner is damaged and can’t be opened. You should move it to the Trash.” Which is always slightly dramatic.

What I did first (and what didn’t work)

At first I assumed the download was corrupted. So I deleted it, re-downloaded it, tried again. Same message. Then I did the usual right-click → Open trick to bypass the simple Gatekeeper warning. Nope. Same “damaged” dialog. That’s when I started thinking this wasn’t actually about corruption.

I even ran:

xattr -d com.apple.quarantine /Applications/FB2Combiner.app

because sometimes it’s just the quarantine flag. Still didn’t launch. So clearly not just that.

What I eventually realized

The “damaged” message on macOS often doesn’t literally mean the app is broken. A lot of the time it’s Gatekeeper blocking an app that isn’t notarized or signed the way Apple expects. And macOS sometimes phrases that block as “damaged,” which is… not the most helpful wording.

Apple explains how Gatekeeper works here:
https://support.apple.com/en-us/102445

And if you want the deeper technical explanation, their developer doc on notarization is here:
https://developer.apple.com/documentation/security/notarizing_macos_software_before_distribution

Basically, if the app isn’t notarized (or macOS can’t verify it), the system may refuse to launch it outright.

What actually helped

Here’s what finally worked for me.

1. I went to System Settings → Privacy & Security.
2. Scrolled down after attempting to open the app.
3. There was a message saying FB2Combiner was blocked.
4. Clicked “Open Anyway.”
5. Confirmed in the next dialog.

After that, it launched normally.

The key detail is that you have to attempt to open the app first, let it fail, and then immediately go to Privacy & Security. The “Open Anyway” option only appears for a short time after the failed launch attempt.

In my case, the app itself was fine. It was just macOS refusing to trust it automatically.

Why this happens with smaller utilities

FB2Combiner isn’t a big App Store product; it’s more of a niche utility for merging FB2 ebook files into one combined file. Tools like this are often distributed outside the Mac App Store, which means they don’t always go through Apple’s notarization pipeline.

If an app is distributed via the App Store, macOS doesn’t complain because Apple has already verified it. For comparison, here’s the general App Store entry point:
https://apps.apple.com/

If FB2Combiner were there, this whole thing probably wouldn’t have happened. But a lot of indie tools live outside that ecosystem.

One more thing I checked

I wanted to make sure it wasn’t an architecture issue (like trying to run an Intel-only binary on Apple Silicon with a weird build). So I quickly checked the app with:

file /Applications/FB2Combiner.app/Contents/MacOS/FB2Combiner

Just to confirm it wasn’t some ancient 32-bit build. It wasn’t. Modern macOS won’t even run 32-bit apps anymore, so that would’ve been a dead end.

Also worth noting: if you see “can’t be opened because Apple cannot check it for malicious software,” that’s slightly different wording, but it’s the same underlying mechanism — Gatekeeper.

I found this page useful while digging through the details and comparing behaviors:
https://bandcinstallersgroup.com/developer/19246-fb2combiner.html

It didn’t magically fix things, but it helped confirm that other people were seeing the same behavior and that the app itself wasn’t fundamentally broken.

Important distinction: “damaged” vs actually damaged

If the app were truly corrupted, you’d usually see it fail even after removing the quarantine attribute or using “Open Anyway.” It might crash instantly, or macOS would refuse to execute it with a different kind of error (like a missing executable or invalid code signature).

In my case, once I explicitly allowed it in Privacy & Security, it ran perfectly. Combined a few FB2 files without issues.

So the problem wasn’t the binary — it was macOS enforcing its security policy.

On newer macOS versions

Apple has been steadily tightening this behavior. Each major release makes it slightly more annoying to run unsigned software. That’s good from a security standpoint, but slightly frustrating when you’re just trying to use a harmless niche utility.

If “Open Anyway” doesn’t appear, sometimes the workaround is:

• Try launching from Finder (not from Spotlight or Launchpad).
• Make sure the app is in /Applications.
• Attempt to open it once to trigger the block.
• Immediately check Privacy & Security.

Occasionally you also need to temporarily disable Gatekeeper via Terminal (spctl --master-disable), but honestly I’d avoid that unless absolutely necessary. It’s overkill for something like this.

What I’ll do differently next time

Honestly, I wasted time assuming the file was broken. Next time I see the word “damaged” on macOS, I’ll interpret it as “security policy conflict” first, not literal corruption.

Quick checklist for future me (and you)

• Try right-click → Open first.
• If blocked, go straight to System Settings → Privacy & Security.
• Look for “Open Anyway.”
• Only mess with xattr if that doesn’t work.
• Avoid disabling Gatekeeper system-wide unless there’s no alternative.

After that, FB2Combiner worked fine. No crashes, no weird behavior, no file permission issues. Just macOS being cautious.

Anyway, figured I’d share in case you ever hit the same thing. It’s one of those small, annoying Mac moments that feels bigger than it is — and once you know what’s really happening, it’s pretty straightforward.