True memory, measured right
Tracks phys_footprint, the same number Activity Monitor's Memory column reports, so a holding process can't hide behind collapsed RSS.
Focused · Lightweight · Essential
Keep your Mac calm, whatever is running.
Halothane is a lightweight memory guard for macOS. It spots runaway processes early and pauses them before they can overwhelm your system.
See how it works
Halothane
✓ system-wide (all accounts)
gauge · pressure
Paused
paused
node (acp-proxy)
98.4 GB
Top memory
Xcode12.8 GB
Chrome exempt9.1 GB
Zed ↗6.4 GB
Photoshop4.2 GB
⏸ Pause monitoring
Settings…Quit
True memorythe same metric Activity Monitor uses
Pause-firststopped processes remain intact and can be resumed
Off by defaultauto-pause is opt-in, per app or globally
All accountsa root helper guards every login session
The reason it exists
One leaky process shouldn't take down your whole machine.
Halothane was born from a real incident: a bug in an ACP proxy made an editor balloon past 100 GB, choking the system and triggering macOS's memory-panic screen. It is the one that force-quits your apps and loses unsaved work.
macOS will happily let a single runaway eat every byte of RAM until the kernel panics. There's no early brake, no "this one process is the problem," only a sudden, system-wide stall. Halothane is that missing brake: a quiet supervisor that spots the runaway early and freezes only the offender, leaving everything else untouched.
The name is the idea. Halothane is an anesthetic, and that's exactly what the app does: it puts a runaway process gently to sleep with a pause, rather than killing it. When you're ready, it wakes back up right where it left off.
How it works
Sample. Warn. Pause.
A tight loop that runs a few times a second, costs almost nothing, and keeps the process under your control. Automatic threshold protection is off by default; at critical macOS memory pressure, Halothane may pause the largest non-exempt process to protect system stability.
01
Sample
Reads every process's true phys_footprint several times a second, including compressed pages that RSS quietly hides.
02
Warn
When a process crosses your threshold or grows too fast, you get a calm heads-up in the menu bar and an always-on-top HUD.
03
Pause
If you've opted in, Halothane freezes the runaway and its whole process tree with SIGSTOP. It can't allocate another byte.
Always-on-top HUD
You see the problem the moment it starts.
A single floating card lists exactly what needs attention: what's warning, what's paused, and the live footprint of each. You get the same one-tap actions everywhere: Resume, Quit, Force-Kill, or Exempt.
- One consolidated card with no notification spam
- Lingers briefly so transient warnings don't flash away
- Dismiss to snooze until something new trips
Everything you need, nothing extra
Built to be invisible until you need it.
Whole-tree freeze
Pauses the offending process and all its children, so a runaway can't dodge the brake by spawning workers.
Growth detection
Catches a fast-climbing process by its rate, not just its size, stopping a leak long before it hits a hard ceiling.
Pressure-coupled
Hooks the kernel's memory-pressure signal. On critical system pressure it pauses the largest non-exempt process automatically.
Per-app rules
LLM inference, VMs, and big builds are supposed to be heavy. Exempt them, or set custom thresholds per app.
Reversible action
Halothane uses the standard POSIX SIGSTOP signal to pause a process tree. Resume sends SIGCONT, allowing the process to continue where it stopped.
Every account, at once
A privileged helper supervises processes across all login sessions, including fast-user-switched accounts.
Featherweight
A pure, UI-free engine sampling a handful of times a second. It lives in your menu bar and stays out of your way.
Snooze anytime
Heading into a heavy workload on purpose? Pause monitoring for 15 minutes, an hour, or until you say so.
Safe & Trusted
Clinical calm and reliability. Halothane pauses processes with a standard, reversible macOS signal and keeps Resume, Quit, and Force-Kill under user control.
Lightweight & Focused
Effortless performance. One small binary doing exactly one job, exceptionally well.
Essential by Design
Everything you need, nothing extra. Sensible defaults, opt-in power, zero noise.
Quick answers
What to know about Halothane.
The practical details for choosing a Mac memory monitor and runaway-process guard.
What problem does Halothane solve?
Halothane watches process memory on your Mac and identifies a process that is using too much memory or growing unusually fast. It warns you early and, when you opt in, can pause the runaway before it freezes the rest of the system.
How is it different from Activity Monitor?
Activity Monitor helps you inspect processes after you open it. Halothane continuously samples the same true memory metric in the background, warns at thresholds you choose, and can pause an opted-in process tree automatically.
Does Halothane automatically kill apps?
No. The currently distributed version pauses processes with SIGSTOP; it does not automatically force-quit them. Resume, Quit, and Force-Kill are deliberate actions you choose.
Can it stop a runaway before the whole Mac locks up?
Halothane is designed to intervene early. It can warn when a process crosses a configured threshold or grows unusually fast. If you enable automatic threshold protection, it can pause the process tree; at critical macOS memory pressure, it may also pause the largest non-exempt process. No user-space utility can guarantee that it will catch every possible allocation before the system becomes unresponsive.
Which Macs are supported?
Halothane supports macOS 14 Sonoma or later on Apple Silicon and Intel Macs. The signed and notarized app is approximately 2 MB.
Does Halothane send process data anywhere?
No. The app runs locally and has no telemetry or analytics. It does not send process names, memory usage, or personal information off your Mac.
Can I exempt memory-heavy work?
Yes. You can exempt apps such as local AI models, virtual machines, and large builds, or give them custom thresholds. Automatic pausing is off by default and can be enabled globally or per app.
Does it monitor every user account?
Yes. A privileged helper monitors processes across all login sessions, including fast-user-switched accounts.
How much does Halothane cost?
Halothane is a one-time $19 purchase with a 14-day money-back guarantee. There is no subscription.
Bring some calm to your Mac.
A one-time $19 purchase. Signed & notarized. Lives quietly in your menu bar, ready the moment something goes wrong.
What the installer does
Installation requires administrator approval. Halothane installs a menu-bar app, a system LaunchDaemon, and a per-user LaunchAgent so its privileged helper can monitor process memory across login sessions.
Automatic threshold pausing is off by default. At critical macOS memory pressure, the current version may automatically pause the largest non-exempt process using SIGSTOP. It does not inject code into other apps, download or execute additional software, collect credentials, or send process names or memory data off your Mac.
Installation and behavior details · Complete uninstall instructions · Source available on GitHub