Cap crashed mid-recording: what you can recover
Cap's WriterFailed crash was reported for months and the maintainer says it was fixed in August 2026. What caused it for different users, what to keep and where the logs are, and how to avoid losing a take.
A crash that eats a recording is the worst thing a recorder can do. Cap's was reported for months, and the maintainer says it is fixed. Here is what happened to the people it hit, and what to do if it happens to you.
The error
In January 2026 a user reported that Cap crashed one to 15 minutes into a recording with: "Task mux-video failed: Error queueing video frame: send_video_frame/WriterFailed/The operation could not be completed." Their setup was an external display, instant mode, a webcam and a USB microphone. They said it happened reliably.
What caused it for different people
The thread collected several setups, and they differ.
- One user narrowed it down to a combination of display scaling and the audio input device, on a MacBook Air M2 with an external monitor, a custom scaled resolution and instant mode on.
- Another hit the same error the moment they started a camera-only recording in studio mode, with the FaceTime camera and microphone and no unusual display scaling. A third confirmed that other modes worked.
- Others wrote that it kept happening after a while, and one called it "arguably the most annoying bug ever" and said they lost several hours to it.
In April 2026 the maintainer replied that it was frustrating, that all resources were on it, and offered $20 for logs and $200 for a fix.
What the maintainer says now
On 2 August 2026 he wrote: "We fixed the instant mode muxer along with mic recovery handling, which addressed this WriterFailed crash (a7b2f146c). This should be in the latest release, please reopen if it still crashes for you." The next day he wrote that his agent had been a little hasty closing the stale issue, but that it was solved months ago.
So if you are on a current version, this specific crash should be gone. If you are on an older one, update first.
If a recording was lost
- Keep the folder. Do not delete the
.caprecording. In one Windows report, issue 2019, a silent crash left the folder withoutproject-config.jsonand with only orphaned video segments. That is the state to keep and attach to a report. - Find the logs. On a Mac they are in
~/Library/Logs/so.cap.desktop, which is where the maintainers ask you to look. - Report it with details. Give the Cap version, the macOS version, your display setup and the mode you used. The maintainers close issues with no version or logs, as one was in August.
- Check the other open crash. Issue 2019 (a silent crash on Windows 11, open since July 2026) and issue 2055 (a recording stopping in the middle, open since July 2026) are still open.
Lowering the risk, on any recorder
- Record a 15-second test with your real setup and play it back before a long session.
- Check the file a few minutes in, not at the end.
- Update the recorder and macOS.
- Avoid changing display scaling or audio devices mid-session.
The same family of failure is in Loom crashed and lost your recording, and the memory side of it is in Cap's CPU and memory use. If the recording survived but had no sound, read Cap recorded no microphone audio, and if it cannot export, Cap export problems.
The best Cap alternatives for Mac compares the options, and Cap's paid tiers are covered separately.
Where Prequel keeps a take
Prequel keeps each take as a folder under ~/Movies/Prequel on your Mac. It holds ordinary files: screen.mp4, camera.mp4, mic.m4a and system.m4a, with a session.json that says when each track started. The folder is self-contained, so you can copy it to another Mac with Prequel installed and it opens the same. See where files live.
Record a short test in Prequel and open the take folder in Finder.
Prequel needs an Apple Silicon Mac on macOS 14 or later. Download Prequel for Mac and try it free for 7 days, with no watermark on anything you export. After that it is $9 a month or $29 once. See what it costs.
Frequently asked questions
- Why did Cap crash with "Task mux-video failed"?
- The error read Task mux-video failed: Error queueing video frame, WriterFailed. Users hit it one to 15 minutes in. One traced it to a combination of display scaling and the audio input device, and another hit it recording camera only in studio mode. Cap's maintainer said in August 2026 that the instant mode muxer had been fixed.
- Can I recover a Cap recording after a crash?
- Do not delete the .cap folder. In one Windows report the folder was left without project-config.json and only orphaned DASH segments, which is the state to keep for a bug report. Cap's desktop logs on a Mac are in ~/Library/Logs/so.cap.desktop.
- Has Cap fixed the WriterFailed crash?
- Its maintainer said on 2 August 2026 that the instant mode muxer and microphone recovery handling were fixed, which addressed this crash, and that it should be in the latest release. He asked anyone still seeing it to reopen the issue.
- How do I avoid losing a screen recording to a crash?
- Record a 15-second test with your exact setup first, play it back, and keep the app and macOS up to date. For long sessions, check the file after the first few minutes rather than at the end.
- Where does Prequel keep a recording while it is made?
- In a folder under ~/Movies/Prequel on your Mac, as ordinary files for the screen, camera, microphone and system audio. It needs an Apple Silicon Mac on macOS 14 or later.
Keep reading
- Loom crashed and lost your recording: what you can get backLoom's own help pages say what can be recovered. Desktop recordings sometimes, Chrome extension and mobile recordings never. The page to try first, the folder to check on a Mac, and how to lower the risk.
- Why Cap uses so much CPU and memory while recordingCap's issue about memory climbing past 5 GB has been open since October 2024 with a $350 bounty. What the maintainers reproduced, three related CPU and heat reports that were closed as reworked, and how to check your own recording.
- Why Cap recorded no microphone audioThe microphone meter moved, and the file had no audio. The pattern 19 comments on Cap's issue 1740 found, which modes were affected, the toggle workaround, the maintainer's fix, and how to check before a long take.
- Cap's export flickers, or never finishesThree open Cap issues about export: flickering and lag in the exported file, an export stuck at the last frame, and a panic before rendering starts. Which macOS and Cap versions, what users tried, and what is still open.
- How to cancel Cap Pro or the Cap Desktop LicenceCap has a free plan, a Desktop Licence and Cap Pro. What each costs, what its own site says about cancelling, what it does not document, and what happens to your recordings and shared links. Checked 5 October 2026.
- Why Cap records what's on top of your windowCap's window capture can record the screen region a window occupies, so another window dragged over it appears in the video. Issue 1754, a user who lost an hour-long workshop, and what Prequel's Window mode records.