Mac

Mac says an app is damaged and can't be opened

Fix "<app> is damaged and can't be opened" or "can't be opened because Apple cannot check it for malicious software" on macOS — the safe Open Anyway path, the quarantine fix for trusted apps, and the override never to use.

Problem summary

I'm here because macOS won't open an app — it says it's 'damaged and can't be opened', or 'can't be opened because Apple cannot check it for malicious software', and offers to move it to the Trash. This is almost always Gatekeeper (macOS's app-safety check), not a literally broken app — and Tahoe tightened it. This page gives the safe fix first (Open Anyway), the quarantine-clearing command for apps you genuinely trust, the malware caveat that comes with it, and the one global override you should never run.

Operator snapshotEvidence first

First proof

Confirm whether you trust the app's source.

Screen to open

xattr -l /Applications/<App>.app

Expected signal

Downloaded yourself from the official site / App Store → safe to override per-app.

Stop boundary

Never on software you can't vouch for.

Layer path

1The 'damaged' / 'cannot be checked for malicious software' message is a Gatekeeper decision, not usually file corruption. macOS quarantines downloaded apps and refuses to run ones that aren't notarized; Tahoe (26.2+) enforces this more strictly, so apps that opened before can now be blocked. The fix is to make a per-app trust decision, not to assume the download broke.

2Because it's a security gate, the safe order is trust-first: confirm the app's source, then use the supported per-app override (Open Anyway), then the targeted quarantine removal for trusted apps. Each step weakens protection for exactly one app you've vouched for — and never for the whole system.

3The dangerous shortcut is the global one: `spctl --master-disable` switches Gatekeeper off for every app, and `xattr -dr com.apple.quarantine` on an unverified app strips the very flag meant to catch malware. The whole method is built to keep system-wide protection on while letting one trusted app through — and to leave untrusted apps blocked.

Runbook

Step-by-step runbook

Start here. Do each check in order, compare it to the expected result, and stop when the evidence explains the failure or the safe stop point applies.

Read the message correctly

Check: Treat 'damaged'/'cannot be checked' as Gatekeeper, not corruption.

Expected result: You approach it as a trust decision, not a re-download reflex.

If not: If genuinely corrupt, re-download later.

Decide trust

Check: Confirm the app came from an official source you chose.

Expected result: You only override for software you vouch for.

If not: Untrusted → Trash it.

Use the supported override

Check: Privacy & Security → Security → Open Anyway.

Expected result: A per-app exception opens it without weakening the system.

If not: No button → targeted quarantine removal.

Clear quarantine (trusted only)

Check: `the "Remove quarantine for a trusted app" command below`.

Expected result: The trusted app opens; protection stays on elsewhere.

If not: Still failing → re-download/verify.

Never go global

Check: Avoid `spctl --master-disable`; re-enable if previously set.

Expected result: System-wide Gatekeeper protection remains intact.

If not: Handle every app individually.

Decision tree

If: App is from a source you don't trust / didn't install.

Then: Gatekeeper is correctly blocking possibly-malicious software.

Action: Move it to the Trash; do not override.

If: Trusted app; 'Open Anyway' button is present.

Then: Unnotarized-but-trusted app blocked by Gatekeeper.

Action: Use Privacy & Security → Open Anyway (the supported per-app path).

If: Trusted app; no 'Open Anyway' (the 'damaged' quarantine case).

Then: Download-quarantine flag triggering the block.

Action: `xattr -dr com.apple.quarantine /Applications/<App>.app` for that app only.

Safe stop: Never on software you can't vouch for.

If: Tempted to silence all such messages.

Then: Global Gatekeeper disable would expose the whole Mac.

Action: Do NOT run `spctl --master-disable`; handle apps individually.

If: Trusted, dequarantined app still won't open.

Then: Genuinely corrupt download or architecture/OS mismatch.

Action: Re-download from the official source; verify with `spctl`/`codesign`.

Evidence

Evidence table

Symptom	Evidence to collect	Likely layer	Next action
'<app> is damaged and can't be opened.'	App was downloaded (has com.apple.quarantine) and isn't notarized.	Gatekeeper + quarantine, not corruption.	Open Anyway, or `xattr -dr com.apple.quarantine` for trusted apps.
'Cannot be checked for malicious software.'	Unnotarized app from an identified/unidentified developer.	Notarization gate.	Privacy & Security → Open Anyway.
Block appeared only after updating to Tahoe.	26.2+ hardened Gatekeeper enforcement.	Stricter enforcement, same app.	Per-app Open Anyway / quarantine removal.
App you didn't install is being blocked.	Unknown provenance.	Possibly unwanted/malicious software.	Delete it; don't override.
Trusted app still fails after dequarantine.	`spctl`/`codesign` show unsigned, or wrong arch.	Corrupt download or architecture mismatch.	Re-download from official source; check arch/OS.

Reference

Commands and settings paths

Inspect the quarantine attribute before acting

xattr -l /Applications/<App>.app

Where: Terminal on the Mac.

Expected: Shows com.apple.quarantine with the download source/timestamp.

Failure means: Its presence confirms the 'damaged' block is quarantine, not corruption.

Safe next step: Decide trust, then remove it (trusted apps only) or delete the app.

Remove quarantine for a trusted app

xattr -dr com.apple.quarantine /Applications/<App>.app

Where: Terminal on the Mac (trusted software only).

Expected: Strips the download-quarantine flag so the app opens.

Failure means: If it still won't open, it may be corrupt or the wrong architecture.

Safe next step: Re-download from the official source.

Read Gatekeeper's verdict and signing status

spctl -a -vv /Applications/<App>.app ; codesign -dv --verbose=4 /Applications/<App>.app

Where: Terminal on the Mac.

Expected: Shows accepted/rejected and the signing identity / notarization.

Failure means: Rejected/unsigned explains the block and whether to trust it.

Safe next step: For unsigned untrusted apps, don't override — delete.

Re-enable Gatekeeper if it was globally disabled

sudo spctl --master-enable

Where: Terminal on the Mac.

Expected: Restores system-wide Gatekeeper protection.

Failure means: If `spctl --status` shows 'assessments disabled', the Mac was exposed.

Safe next step: Keep it enabled; use per-app overrides instead.

Hardware boundary

Hardware and platform boundary

Change only when

Prefer apps from the Mac App Store or notarized developers — they open without any of this, because they pass Gatekeeper cleanly.
For your own builds (developers), use a Developer ID certificate or ad-hoc signing instead of disabling Gatekeeper.

Evidence that matters

The app's source and notarization status — that's what the message is about.
Per-app overrides (Open Anyway / targeted quarantine removal), not global ones.
A way to verify signing (`spctl`, `codesign`) when in doubt.

Evidence that does not matter

Whether the file is literally 'damaged' — it usually isn't; it's a trust gate.
The exact wording ('damaged' vs 'cannot be checked') — both are Gatekeeper.
Third-party 'unlocker' tools — the built-in steps are safer.

Avoid

`sudo spctl --master-disable` — it disables Gatekeeper for the whole Mac.
`xattr` quarantine removal on software you can't vouch for.
Following a website's bypass steps to install 'free' paid software (malware vector).

Related tool/checklist

Use the linked tool when you need a guided plan from your exact symptoms instead of a static checklist.

Backup plan builder

Last reviewed

2026-06-02 · Reviewed by HomeTechOps. Reviewed against Apple's 'Safely open apps on your Mac' guidance and the Tahoe Gatekeeper hardening; frames the 'damaged'/'cannot be checked' message as a Gatekeeper/notarization trust decision, leads with the supported Open Anyway path and trusted-only `xattr` quarantine removal, and is explicit that `spctl --master-disable` (and dequarantining untrusted apps) is the override never to use.

Sources/assumptions

Assumes a Mac on macOS Tahoe (macOS 26), where Gatekeeper/notarization enforcement was hardened (26.2+); exact wording of the block varies (‘damaged’ vs ‘cannot be checked’).
Commands (`xattr`, `spctl`, `codesign`) follow Apple's documented behaviour; `xattr` quarantine removal is appropriate only for trusted software.
The advice assumes you can verify the app's source; for unverifiable apps the safe action is not to override Gatekeeper.

Source-backed checks

HomeTechOps turns official docs and conservative safety rules into a shorter runbook. These links are the source trail for the page direction.

Apple Support: Safely open apps on your MacUsed for Gatekeeper/notarization behaviour and the supported 'Open Anyway' path in Privacy & Security, versus risky blanket overrides; the safe way to handle an 'app is damaged / can't be opened' message.Apple Support: macOS Tahoe 26 — what's included in the updates (KB 122868)Authoritative per-point-release version + date list for macOS Tahoe 26.x; cited to pin which point release a Time Machine / Wi-Fi / dock symptom maps to.

Diagnostic rule

1. Check the simplest signal first.
2. Change one thing at a time.
3. Avoid unsafe electrical or data-loss steps.
4. Stop when the evidence says the risk moved.

FAQ

Why does my Mac say an app is 'damaged and can't be opened'?

Usually it's not actually damaged — it's Gatekeeper blocking an app that isn't notarized, combined with the download-quarantine flag, which macOS Tahoe (26.2+) enforces more strictly. For an app you trust, open it via System Settings → Privacy & Security → Open Anyway, or clear the quarantine flag with `xattr -dr com.apple.quarantine /Applications/<App>.app`. If it's genuinely corrupt, re-download it from the official source.

Is it safe to run `xattr -dr com.apple.quarantine` on an app?

Only for software you genuinely trust and downloaded yourself from an official source. That command removes the quarantine flag macOS uses to flag potentially malicious downloads, so running it on an app you can't vouch for removes a real safety check. For trusted apps it's a targeted, reasonable fix; for unknown apps, don't.

Should I use `spctl --master-disable` to fix this?

No — never. `sudo spctl --master-disable` turns off Gatekeeper for every app on your Mac, leaving you exposed to genuinely malicious software. Handle trusted apps one at a time with 'Open Anyway' or per-app quarantine removal instead. If you've already run it, re-enable protection with `sudo spctl --master-enable`.

The app still won't open after clearing quarantine — now what?

Re-download it fresh from the developer's official site or the App Store, since a partial or corrupted download can genuinely be 'damaged'. You can also check it's properly signed with `spctl -a -vv /Applications/<App>.app` and `codesign -dv --verbose=4`, and confirm it's built for your Mac's architecture and macOS version.