Video calls have become one of the most demanding things most people ask their Mac to do on a regular basis. Unlike writing a document or browsing the web, a live video call requires the CPU to work continuously, every second, for as long as the call runs. Zoom is generally good at this relative to its competition, but no app can make video encoding cheap. The question isn't whether Zoom uses significant CPU, because it does, but whether what you're seeing is normal and what you can reasonably do about it.
The short answer is that 15-30% CPU during a normal call on an M-series Mac is typical and expected. Screen-sharing or breakout rooms push that to 30-50%. Neither figure means something is wrong. Understanding why those numbers look the way they do makes the rest of this clearer.
Why does Zoom use so much CPU?
A video call has several simultaneous jobs. Zoom is encoding your outgoing video in real time, decoding incoming video from every other participant, running noise suppression on your microphone feed, processing the speaker's audio, and managing the network transport for all of it. Each of those tasks runs continuously for the entire call. There is no quiet moment where the CPU can coast.
On modern M-series Macs, Zoom uses Apple's VideoToolbox and Metal APIs to push encoding and decoding onto the chip's dedicated hardware video engine and GPU rather than the main CPU cores. This is on by default and is a meaningful efficiency gain. A Zoom call that might consume 50-60% CPU on an older Intel MacBook Air runs at 20-30% on an M2 MacBook Air partly because the work has been offloaded to silicon designed specifically for it.
What you see as "Zoom" in Activity Monitor is actually several processes working together. The main zoom.us process handles the interface, chat, and call management. CptHost is the camera and screen capture process. zoomzr manages caption rendering when live captions are on. Various helper processes handle audio and networking in the background. When you sum them up, the total is higher than any one entry suggests.
Is Zoom CPU usage on Mac normal?
Yes, within the ranges below. These figures apply to M-series Macs:
- Idle, no call: 1-3% CPU. Zoom keeps a small process running even when you're not in a meeting to handle incoming call notifications.
- Normal video call, few participants: 15-30% CPU across all Zoom processes. This is the expected baseline for a standard meeting.
- Screen-sharing: 30-50% CPU. Zoom is now capturing, encoding, and transmitting your screen continuously in addition to video and audio. If you're sharing across multiple monitors, the load is higher still, because each display's content must be captured and encoded.
- Large meeting with breakout rooms: CPU rises further. Zoom handles the switching infrastructure and keeps multiple channel connections alive simultaneously.
Intel Macs see higher numbers across all categories because they lack the dedicated hardware video encoders that Apple's own silicon has. A call that runs at 25% on an M1 MacBook Pro might run at 45-55% on an equivalent Intel model, with more heat and shorter battery life as a result.
Compared to Microsoft Teams, Zoom is generally the more efficient app for equivalent call types. Teams carries its Electron browser overhead even outside of calls. Zoom's native Mac architecture is leaner at rest, and its use of VideoToolbox gives it an efficiency advantage on Apple silicon that Electron-based apps don't get as readily.
Why your Mac slows down during calls
The relationship between Zoom's CPU usage and your Mac feeling slow is real but indirect. The mechanism is thermal management rather than resource competition.
When Zoom runs a call, the CPU works hard continuously for as long as the meeting lasts. Sustained CPU load generates heat. On MacBook models especially, the thermal system responds to rising chip temperatures by reducing clock speeds across the whole processor, not just the Zoom-related cores. This is called thermal throttling, and it's macOS protecting the hardware. The side effect is that other apps slow down during a heavy Zoom call because the processor is running at reduced speed to stay within safe temperature limits.
On desktop Macs or MacBook Pros with better thermal headroom, this is less pronounced. On MacBook Air models, which have no fan and rely entirely on passive cooling, a long screen-sharing session can trigger sustained throttling that makes the whole machine feel sluggish. If your Mac is running hot during calls, see why your Mac runs hot for a fuller explanation of what's happening and what helps.
There's a separate memory angle too. Zoom itself doesn't use vast amounts of RAM, typically 300-600 MB depending on the call, but the background services that keep running after you close the window accumulate over time. By the end of a heavy call day, the combination of Zoom's processes and other open apps can push macOS into memory pressure, which adds to the sluggishness. For a broader view of why your Mac gets slow, why is my Mac so slow covers the main causes together.
How to reduce Zoom's load
Several features in Zoom require continuous real-time computation. Turning them off has a meaningful effect on CPU usage:
Disable virtual backgrounds. Virtual background processing runs a machine learning model on every video frame to separate you from your background. This is the most CPU-intensive optional feature in Zoom. Even a static image background costs significantly more than no background at all. Go to Zoom settings, Video, and turn it off when you don't need it. On calls where appearance matters less, a physical background or a tidy room costs nothing.
Turn off “Touch up my appearance”. This filter runs real-time image processing on your video to smooth the image. Like virtual backgrounds, it operates on every frame. It's in the same Video section of settings. The CPU saving from disabling it is modest but consistent, and it compounds with other changes.
Disable HD video when you don't need it. HD video requires encoding at higher resolution and bitrate, which increases the encoding workload. In lower-stakes calls or calls where your video thumbnail is small on other participants' screens, standard definition is indistinguishable. Video settings in Zoom let you uncheck HD.
Share one screen, not all of them. If you have multiple monitors connected and you share your entire desktop, Zoom captures and encodes every display. Sharing a single window or a specific application instead of the whole screen dramatically reduces the screen capture load. The option appears when you click Share Screen in a call.
Join audio-only for non-essential calls. Removing your camera from a call eliminates video encoding entirely and cuts CPU usage by roughly half. Most video call apps including Zoom make this easy. If you're on a call where you don't need to be seen, turning the camera off is the single fastest way to reduce Zoom's load.
Quit Zoom fully after calls. Closing the Zoom window does not quit the app. Background helper processes keep running to handle incoming calls and notifications, and any memory that accumulated during the session stays allocated. Pressing Command-Q quits Zoom completely. This is especially important if you've had several calls through the day: a fresh Zoom launch tomorrow starts clean, with no accumulated state from today's sessions.
What to do if your Mac slows down during calls
If your Mac feels noticeably slower during Zoom calls specifically, a few targeted steps help:
Close unused apps before a call starts. Fewer running apps means less baseline CPU and memory demand, which gives the thermal system more room to handle Zoom's sustained load without throttling other things. Slack, in particular, can add meaningful background CPU overhead. The two together on a busy day add up; for details on Slack's own footprint, see Slack on Mac: memory usage and what to do about it.
Check Activity Monitor during a call. Press Command-Space, type “Activity Monitor”, and switch to the CPU tab. Sort by % CPU descending. If something other than Zoom is near the top, that's a secondary contributor worth addressing. Sorting by Memory and checking the Memory Pressure graph at the bottom of the Memory tab tells you whether memory is also a factor. Apple's own guide on using Activity Monitor on Mac covers how to read what you're seeing.
Plug in if you're on battery. When a MacBook runs on battery, macOS applies additional power limits that can make CPU throttling more aggressive. Connecting the charger gives the thermal system more room to sustain performance under load.
Consider the web version for short check-ins. Opening zoom.us in your browser rather than launching the desktop app can work for brief calls where you're joining but not hosting or screen-sharing. It doesn't have access to Zoom's hardware acceleration in the same way, but it avoids Zoom's background services entirely and leaves no residual processes when you close the tab. For full meetings with screen-sharing or larger groups, the desktop app is the better choice.