The safest current workaround is to change your MacBook’s built-in display refresh rate from ProMotion to 60 Hz while using Stremio’s native macOS player. Go to System Settings → Displays → Refresh Rate → 60 Hz; the reported playback session improved immediately without restarting Stremio or changing the stream. If the problem returns when ProMotion is restored, keep 60 Hz enabled during playback until a Stremio or macOS update addresses the rendering issue.
What this Stremio problem looks like
This issue affects video playback in the native macOS app on Macs with a ProMotion display. Typical signs include:
- WindowServer staying close to 100% CPU in Activity Monitor.
- The Mac becoming warmer than expected during playback.
- Faster battery drain or unusually high power use.
- Stremio itself and the video decoder using much less CPU than WindowServer.
- The problem appearing with the built-in display set to ProMotion and easing when the refresh rate is changed to 60 Hz.
The reported case involved Stremio Native 2.0.4 (19), an Apple M4 Pro MacBook Pro, HEVC video, and the native KSPlayer/Metal player. Those details help identify a similar report, but they do not prove that every high-CPU case has the same cause.
Why WindowServer may be using so much CPU
WindowServer is a macOS system process responsible for composing and displaying app windows and rendered graphics. In the reported case, video decoding was confirmed through Apple VideoToolbox, while rendering involved Metal and an MTKView. This makes an inefficient interaction between the native player’s frame-rendering cadence and ProMotion’s variable refresh behavior a plausible explanation.
That is still a working theory, not a confirmed root cause. The report does not establish that HEVC, hardware decoding, a particular stream, or every ProMotion configuration independently causes the problem. The unusually high usage may instead depend on the combination of Stremio version, macOS build, display, player, refresh rate, and video.
Fix 1: Switch the display to 60 Hz
This is the least destructive and currently best-supported workaround for the reported behavior.
- Stop other demanding tasks if you want a clearer comparison.
- Open Apple menu → System Settings.
- Select Displays.
- Select the built-in MacBook display if more than one display is shown.
- Find Refresh Rate and choose 60 Hz rather than ProMotion.
- Return to Stremio and continue the existing playback session.
- Wait at least 30 seconds, then check Activity Monitor again.
The exact label can vary slightly between macOS releases, but the setting is under the affected display’s options. The reported test found that changing only this setting reduced WindowServer usage immediately, with no Stremio restart and no change to the active stream.
Using 60 Hz is a workaround, not a permanent repair. It may reduce the smoothness of general scrolling and other interface animations compared with ProMotion, but it should not require reinstalling Stremio or altering your account, addons, or media library.
Fix 2: Confirm that the refresh rate is the trigger
Before making more disruptive changes, reproduce the comparison carefully:
- Open Activity Monitor and select the CPU tab.
- Start the same Stremio stream on the same display.
- Let playback continue for at least 30 seconds.
- Note the approximate CPU use for WindowServer, Stremio, and any related playback process.
- Change the display to 60 Hz while playback continues.
- Wait another 30 seconds and compare the results.
A clear drop in WindowServer usage after changing only the refresh rate strongly matches the reported ProMotion-specific symptom. Do not treat a single short spike as proof of this bug: macOS may briefly use additional CPU while switching displays, opening windows, or performing other background work.
If WindowServer remains high at 60 Hz, this may be a different problem. Check whether the usage is caused by another app, an external display, screen recording, visual effects, or a general macOS graphics issue rather than Stremio playback alone.
Fix 3: Relaunch Stremio and test a different session
The report did not require a restart, but relaunching is a safe diagnostic step if the refresh-rate change does not help consistently.
- Stop playback.
- Quit Stremio completely with Stremio → Quit Stremio or Command-Q.
- Wait a few seconds and open Stremio again.
- Test the same stream at 60 Hz.
- If it is stable, test another video only if needed for comparison.
Avoid repeatedly changing streams while diagnosing the issue. A different resolution, frame rate, codec, HDR mode, or rendering workload can make the comparison inconclusive. If the problem occurs only with one video, record its codec and quality rather than assuming the stream is defective.
Fix 4: Check for app and macOS updates
Because the report is version-specific, check whether a newer Stremio Native release is available and install it only from Stremio’s normal official distribution channel. Also install a compatible macOS update if one is offered through System Settings → General → Software Update.
After updating, retest ProMotion and 60 Hz separately. A later version may change the result, but an update should not be described as a confirmed fix unless your own test shows that WindowServer no longer becomes unusually busy.
If the issue began immediately after an update, keep using 60 Hz as the fallback and include the old and new app versions in a bug report. Do not downgrade macOS or replace system graphics components as a first response.
What worked for affected users
The GitHub reporter found that switching the built-in display from ProMotion to 60 Hz reduced WindowServer from approximately 98% CPU to approximately 8% during the comparison. Reported battery draw also fell from about 17 W to about 3.6 W. The same Stremio process IDs and playback session reportedly remained active, so the change was not attributed to restarting the app or selecting a different stream.
This is useful evidence for a refresh-rate-related rendering problem, but it is still a community report from a particular Mac, macOS build, Stremio version, player, and HEVC playback session. It is not a universal guarantee. Other users may see smaller changes, no change, or high CPU caused by another component.
Community addons are independently operated from the Stremio application. Changing an addon is therefore not an established fix for this WindowServer symptom, and the reported comparison did not demonstrate that an addon caused it. If you test another source, keep the display refresh rate, video quality, and playback conditions consistent so the result remains meaningful.
When to report the problem
Report the issue if WindowServer still approaches one full CPU core at ProMotion, especially if 60 Hz reliably resolves it. Include:
- Stremio version and whether it is the native macOS app.
- Mac model and chip.
- macOS version and build.
- Internal or external display and selected refresh rate.
- Video codec, resolution, HDR status, and player information if available.
- WindowServer, Stremio, and decoder CPU observations.
- Whether changing only the refresh rate helped.
Avoid posting account credentials, private addon configuration, or media-provider login details. Until the behavior is corrected, use 60 Hz during Stremio playback and restore ProMotion afterward only if the added battery and CPU use are acceptable.
FAQ
Do I need to restart Stremio after selecting 60 Hz?
Not according to the reported test. The reduction occurred during the existing playback session. Relaunch Stremio only as a diagnostic step if the change does not apply reliably.
Is hardware decoding broken?
The report specifically indicated that HEVC hardware decoding through VideoToolbox was active. High WindowServer usage therefore should not automatically be interpreted as a decoder failure.
Can I keep ProMotion enabled outside Stremio?
Yes. A practical fallback is to switch to 60 Hz while watching video in the native app and return to ProMotion afterward. Whether that is worthwhile depends on how consistently the problem occurs on your Mac.
Last reviewed: August 29, 2026