Why you'd combine clips instead of keeping them separate
Multiple recordings of the same event (a long meeting split into several files by a recording app), separate takes of the same scene, or a sequence of short clips meant to play as one continuous piece all need to become a single file before they can be uploaded as one video, played back without manual switching, or edited as a unified timeline elsewhere.
Merging solves this directly: the clips play in the order you arrange them, back-to-back, in one output file, with no gaps or manual intervention needed between them.
The gotcha: mismatched formats between clips
The smoothest merges happen when all the source clips share the same resolution, frame rate, and codec — footage from the same camera or app in one session usually qualifies. Mixing a 1080p clip with a 4K clip, or footage at 30fps with footage at 60fps, forces a decision about which specs the combined output should use, and the mismatched clips need to be resized or reframed to match, which can look like a visible jump in quality or aspect ratio at the join point.
If your clips came from different devices or apps, it's worth checking their resolution and frame rate before merging — matching them up first, or at least being aware they don't match, avoids surprises in the combined result.
Order matters and it's easy to get wrong
Merging plays clips in whatever order you arrange them, so double-checking the sequence before processing saves having to redo the entire operation. This matters more than it sounds — clips from a phone gallery aren't always sorted chronologically the way you'd expect, especially if some were trimmed or edited after recording, which can shuffle their timestamps.
A quick preview of each clip's first few seconds before finalizing the order is a small habit that avoids the most common merge mistake.
What happens to audio at the join points
Each clip's own audio carries through into the merged file exactly as it was in the source — there's no automatic crossfade or volume matching between clips, so if one clip is noticeably louder or quieter than the next, that difference will be audible at the transition. For a polished result across clips recorded at different volumes, some manual audio leveling afterward in a dedicated editor may be worth the extra step.
For most everyday use — combining split recordings of the same continuous event — audio levels are usually consistent enough that this isn't noticeable, since it's really the same recording session split into pieces rather than genuinely separate sources.