Should I blur faces in CapCut or use a face blur app?

Use CapCut if you are already editing there and have one or two faces to hide in a short clip: the mask-and-keyframe method works and costs nothing. Use a face blur app such as Anonimo when there are many faces, when the people move, or when the footage should not be uploaded anywhere: detection is automatic, each person is one tap, and it runs on the phone.

How blurring works in CapCut

Duplicate the clip as an overlay above itself.
Apply a blur or mosaic effect to the overlay.
Mask the overlay to a circle over the face.
Keyframe the mask position every time the face moves, for every face.

Count on a few minutes per face per minute of video, more if the person walks across the frame. Any face you miss, or any keyframe you forget, shows the face.

How a face blur app works

Anonimo detects every face in every frame, groups them by person, and tracks each face between detections. You tap the people who stay visible; the rest are covered for the whole clip. Pixelation, blur or emoji, exported at source resolution with Pro. It runs offline on the iPhone and never uploads the video.

If you want this done automatically on your iPhone, Anonimo finds every face in a video, groups them by person, and blurs everyone except the people you pick. Nothing leaves the phone.

Trade-offs

CapCut is a full editor: cuts, captions, music and the blur in one place. Anonimo does one thing; you may still edit elsewhere.
CapCut's blur is wherever you put it. Anonimo's is wherever it found a face, plus a head estimate where a face turns away, so check the export.
CapCut is free with optional Pro features, and some of its features process in the cloud. Anonimo is free up to 30 seconds and entirely on-device.

Questions

Does CapCut blur faces automatically?

Its reliable method is manual: a blurred overlay, a mask and keyframes. Check the current version for any automatic option and whether it processes in the cloud.

Can I blur a face in CapCut and then finish editing in CapCut?

Yes, that is CapCut's advantage. With Anonimo you blur first, export to Photos, then edit the blurred clip in any editor.

Which is better for a vlog with strangers in the background?

The app. Background faces are many, small and moving, which is exactly what manual masking is bad at and automatic detection is for.