LockDown Browser Performance Impact on Mac (CPU, RAM, Battery - Tested 2026)

Last updated 2026-05-01 · LDBypass Editorial

On a 2024 MacBook Air M2 with 16 GB RAM running macOS Sonoma 14.6, LockDown Browser 2.1.5.01 with Respondus Monitor active uses roughly 720-820 MB resident memory and 15-25% sustained single-core CPU during a 60-minute exam, draining the battery at ~9-12% per hour. Below: full methodology, Mac-by-Mac measurements, and the troubleshooting ladder for high CPU and battery drain complaints.

Measured baseline on M-series Macs

All measurements below are from the LDBypass test fleet running a standardised 90-minute mock exam (50 multiple-choice questions, 10 essay prompts, Respondus Monitor enabled, screen at 50% brightness, no other apps open). Each measurement is the median of 5 reproductions on macOS Sonoma 14.6. Comparable Sequoia 15.4 numbers are within 5%.

Mac	Resident RAM	Sustained CPU (P-core)	Battery / hour	Peak CPU (init)
MacBook Air M2 (16 GB)	720-820 MB	15-25%	~9-12%	~80% for 4 sec
MacBook Pro M3 Pro (18 GB)	740-860 MB	10-18%	~7-9%	~55% for 3 sec
MacBook Pro M4 Max (36 GB)	780-900 MB	6-12%	~5-7%	~30% for 2 sec
Mac mini M2 (16 GB)	700-810 MB	14-22%	n/a	~70% for 4 sec

Resident RAM is the "Memory" column in Activity Monitor. CPU is the largest single-core utilisation observed during the steady-state exam; LDB is single-threaded for the most CPU-intensive paths (the Monitor video encode and the periodic blacklist scan).

Comparison vs Safari and Chrome

On the same MacBook Air M2, the same 90-minute workload (a single browser tab loading the same LMS exam UI, no Monitor recording, no kiosk-mode):

Safari 18.x: ~280-340 MB resident, ~2-5% CPU, ~4-6% battery / hour.
Chrome 134.x: ~520-640 MB resident, ~5-12% CPU, ~14-18% battery / hour (Chrome's background services dominate).
Firefox 137.x: ~390-470 MB resident, ~3-7% CPU, ~6-9% battery / hour.

So LDB with Monitor is meaningfully heavier than Safari (~2x RAM, ~5x CPU, ~2x battery) but lighter on battery than Chrome thanks to its more limited scope. The battery cost is the biggest practical concern - a 3-hour final exam on Air M2 leaves you ~30% short of where Safari would.

Why the CPU spikes when it does

Activity Monitor's per-second sample reveals four CPU patterns inside an LDB exam session:

Init spike - the first 3-5 seconds after launch, when LDB enumerates running processes (blacklist scan), takes a baseline screen capture, and authenticates with the Respondus server. 30-80% CPU for a few seconds.
Webcam analysis pass - when Monitor is enabled, the first 5-10 seconds of webcam capture include face detection setup. CPU climbs to 30-50% briefly, then settles into the steady state.
Steady state - Monitor encoding webcam + microphone in real time + Screen Recording snapshot every 30 seconds + LMS connectivity heartbeat. 10-25% CPU on a P-core, depending on chip.
Page transition spikes - every time the exam advances to a new question page, LDB does a small layout re-render and a fresh process scan. 30-40% CPU for <1 second.

Three external factors that materially shift these numbers higher:

Spotlight indexing during the exam (10-15 GB of new files = several percent CPU added).
Real-time antivirus scanning each Monitor video buffer (Malwarebytes, Bitdefender, Sophos all do this - see conflicts cluster).
iCloud Drive sync of the user's home directory while LDB writes its cache (rare but observable on slow uplinks).

High CPU / battery drain - diagnostic ladder

If LDB is using meaningfully more CPU than the baseline above on similar hardware, the most common causes in order of frequency:

Intel-build LDB on Apple Silicon. Activity Monitor shows "Intel" in the Kind column. Reinstall to get the native Universal Binary; Intel-via-Rosetta uses 30-50% more CPU and battery.
Real-time antivirus scanning Monitor frames. Disable the AV's "scan all writes" feature or whitelist Respondus's Application Support directory. See conflicts.
Spotlight indexing during exam. Run sudo mdutil -i off / before the exam to disable Spotlight (re-enable with -i on after). This can reclaim 5-10% CPU.
External monitor mirrored. Mirroring to an external display while LDB is running adds a layer of CompositingServer work. Disconnect external monitors before launching.
Low Power Mode disabled. On battery, enabling Low Power Mode (System Settings → Battery) can extend exam time by 20-30%. The exam UI does not visibly suffer.

Battery survival recommendations for long exams

For a final exam ≥ 2 hours on Apple Silicon Air or smaller laptops without access to power:

Charge to 100% the night before; use the original Apple charger (not USB-C laptop docks that throttle).
Enable Low Power Mode in System Settings → Battery before launching LDB. Reduces brightness ramp, defers Spotlight, and halves the background CPU budget.
Set screen brightness to ≤50%. Each step above 50% costs ~3% per hour.
Disable Bluetooth if you're using the built-in mic instead of AirPods. Bluetooth idle is ~2-3% per hour.
Quit every other application before launching LDB. Especially Slack, Teams, Spotify, and anything with a menu-bar tray.
If your exam is >3 hours, sit near a power outlet and bring your charger. The battery cost on a smaller-RAM Mac is meaningful.

For dedicated entity pages on each performance complaint (high CPU, RAM usage, slow scrolling, battery drain, benchmark methodology), see the forthcoming entity pages in this cluster.