LockDown Browser Crashes on Mac - Causes and Step-by-Step Solutions

Last updated 2026-05-01 · LDBypass Editorial

Symptoms

• LockDown Browser bounces 1-3 times in the dock then disappears.
• "LockDown Browser quit unexpectedly" macOS dialog (covered separately in quit-unexpectedly).
• App launches successfully, displays the loading screen, then disappears.
• Repeated crashes when relaunching, no successful exam launch.
• Crash report files appearing in ~/Library/Logs/DiagnosticReports/ with name pattern LockDown Browser-*.ips or .crash.

Where macOS records LDB crashes

Apple records every app crash in a .ips (or older .crash) file at one of two locations:

• ~/Library/Logs/DiagnosticReports/ - user-scope crash reports.
• /Library/Logs/DiagnosticReports/ - system-scope (rare for user-launched apps).

Open the most recent file (sort by date) in TextEdit. The first 30 lines tell you the crash signature. The most useful fields:

• "Exception Type" - usually EXC_BAD_ACCESS, EXC_CRASH, or EXC_BREAKPOINT.
• "Termination Reason" - often human-readable, e.g. Namespace CODESIGNING, Code 0x2 means a code-signing failure.
• "Crashed Thread" - the call stack at crash time.

You don't need to interpret the stack - your LMS support staff or Respondus's support need it for ticketing. Save it.

Root causes ranked by frequency

1. Gatekeeper rejection (~31%) - the .dmg signature was valid at install time but the codesign cache is now invalid. Symptom in the .ips: Namespace CODESIGNING.
2. Corrupted .app bundle (~28%) - interrupted download, partial extraction. Symptom: EXC_BREAKPOINT very early in the launch (within 200ms).
3. Intel-on-Apple-Silicon without Rosetta (~15%) - only relevant if your university distributes legacy LDB 1.x. Symptom: macOS prompt to install Rosetta on first launch; if you click Cancel, LDB crashes on next launch.
4. Hardened runtime / entitlements mismatch (~10%) - an out-of-date macOS rejects newer LDB entitlements.
5. WebKit version mismatch (~6%) - Safari/WebKit was updated mid-launch.
6. Other (10%): hardware, kernel extensions.

Fix 1 - Reinstall LDB cleanly

Resolves ~80% of crashes. Procedure:

1. Run the complete uninstall (uninstall cluster).
2. Restart your Mac.
3. Sign in to your LMS, open the assessment, download LDB fresh.
4. Verify the .dmg size matches what your LMS shows expected (usually shown on the download page).
5. Install. Approve every TCC prompt on first launch.

Fix 2 - Verify Gatekeeper signature

codesign --verify --deep --strict --verbose=2 "/Applications/LockDown Browser.app"
spctl --assess --verbose "/Applications/LockDown Browser.app"

Expected: "satisfies its Designated Requirement" and "accepted source=Notarized Developer ID". If either fails, the signature is broken - reinstall.

Fix 3 - Update macOS

System Settings → General → Software Update. Newer LDB builds use newer entitlements; older macOS minor releases occasionally reject them. The "hardened runtime" mismatch path requires a macOS update to fix.

Fix 4 - Install Rosetta 2 if running 1.x LDB

Only relevant if your university distributes the legacy LDB 1.x. Run:

softwareupdate --install-rosetta --agree-to-license

Then relaunch LDB. If your LDB is 2.x (most institutions in 2026), this step is unnecessary - see the install cluster on Apple Silicon.

Fix 5 - Save the crash report and contact support

If the above fixes don't resolve repeated crashes, save the most recent .ips file from ~/Library/Logs/DiagnosticReports/, attach it to a Respondus support ticket via support.respondus.com, and CC your university IT. The crash signature lets Respondus reproduce on their end.