How do I trim a video cleanly without leaving a black frame at the cut?

Start by treating the cut as a small area to inspect, not just a single timeline boundary. Zoom in around the edit and check that the outgoing clip reaches the cut and the incoming clip begins where you expect. Look for a visible empty space between clips, a clip edge that stops short, or a transition you did not intend. Then play through the edit from a little before the cut to a little after it. A still image of the timeline can be misleading; previewing shows whether the change looks and sounds abrupt. If you are using iMovie for Mac 10.4.1 on macOS 13.5, Apple documents the Precision Editor as a way to expand the outgoing and incoming clips around an edit point and adjust their starts and ends; it can also show and adjust an attached transition. [S1] Other editors may name or arrange similar controls differently, so use the timeline and preview tools available in yours.

In iMovie for iPhone, pinch open on the timeline to zoom in, then scrub through the area to preview it in more detail. [S2] This can make the edit easier to inspect, but Apple’s guidance does not claim that this view provides frame-by-frame accuracy. [S2] Don’t assume a close-looking timeline view proves the cut is clean: play across the edit, and verify the exported video separately. If your editor offers a more precise trimming view, use it to adjust the clip ends, then preview again. If you cannot confidently inspect a suspicious cut on the phone, keep a note of its approximate position and review it on a larger screen or in a tool with a more detailed edit view.

Use the same short review for every cut that looks questionable:

1. Note the location, such as [00:01:24], and identify the two clips at that edit.
2. Zoom in or open a precision editing view if available. Check both clip edges and any transition shown at the boundary.
3. Preview from before the outgoing clip ends until after the incoming clip is underway. Watch for black, a frozen image, a flash, or an unintended fade; listen for an unexpected pause or audio change too.
4. Adjust the edit, then replay it. Repeat until the transition matches your intention.
5. Export, open the rendered file, and watch the same section again. The timeline preview is not a substitute for checking the rendered result; Apple’s iMovie guidance also recommends checking the final rendered video separately. [S1][S2]

For example, your review note could read: Cut at [00:01:24] — outgoing: [shot A]; incoming: [shot B]; intended: direct cut; preview: [pass/recheck]; export check: [pass/recheck]. These labels are placeholders, not a special format. If the exported file still shows black, return to that location in the project and inspect the clip edges and transition again.

Make a short cut-review log rather than relying on memory. Use one line per edit: Time | outgoing clip | incoming clip | intended edit | preview result | exported-file result | action. Write recheck instead of pass whenever you are uncertain, and avoid changing several cuts at once; that makes it easier to tell which adjustment affected the result. If a cut remains ambiguous, compare the timeline around it with playback of the rendered file at the same approximate location. A zoomed timeline or scrub preview can help you inspect an edit, but the available guidance does not establish that every editor can display each frame or that a preview guarantees a gap-free export. [S1][S2] The useful confirmation is watching the exported section. Keep the project and review notes until you have finished checking the cuts you flagged.