How to Crop a Video (Trim, Cut, or Resize the Frame)

"Crop a video" is one of those phrases that means different things to different people. Three actual operations live under that umbrella, and they need different tools:

1. Trim — shorten by dropping the start or the end. You keep one continuous range from the middle of the timeline.
2. Cut — remove a segment from the middle. Two surviving pieces get joined back together.
3. Resize the frame — change the visual dimensions of the video (e.g. crop a 16:9 clip into a 9:16 vertical for TikTok).

This guide walks through each one, in order of how common they are.

1. Trim (drop start / end)

The most common "crop" — you have a 5-minute screen recording but only the middle 2 minutes are useful. Video Trim handles this. Drop the file, set the in-point and out-point on the scrubber, click Trim, download.

Two technical notes:

• Stream copy is fast, re-encode is slow. If the trim cuts on a keyframe boundary, ffmpeg can copy the streams without re-encoding (operation takes seconds regardless of clip length). If it doesn't, it has to re-encode the surrounding GOP, which takes ~the duration of the clip. Most tools (including Dropvert's) default to keyframe-aligned trim and bump to re-encode only if the user picks a non-aligned point.
• Trimming preserves quality. No re-encoding loop = no quality loss. The output is bit-identical to the source for the surviving range.

2. Cut (remove a middle segment)

Less common but a real need — "remove the bit between 0:30 and 0:45". Video Cut handles this by trimming twice and concatenating the two surviving pieces.

Concatenation has one important gotcha: the two pieces must share the same codec, resolution, and pixel format. If they don't, ffmpeg re-encodes. Since both pieces come from the same source file, this almost always works without re-encode — but if you're cutting a clip you've already trimmed with a different tool that re-encoded mid-clip, the pieces may have drifted slightly and a re-encode kicks in.

3. Resize the frame (change dimensions)

"Crop the video to 1080×1080 for Instagram." This is the operation people most often call "crop" but most generic crop tools don't do well — most just shrink the whole frame and add letterbox bars, which isn't a true crop.

For frame resize, Video Compress has a Resolution dropdown that downscales while preserving aspect ratio. For a true crop (e.g., 16:9 → 9:16 by chopping the sides off, not letterboxing), you'd need a tool that exposes ffmpeg's crop filter directly — which Dropvert doesn't surface today.

Workaround for true frame crop: use a free desktop tool like Shotcut or HandBrake. Both expose a crop filter explicitly and run locally on your machine — no upload.

Quick reference

You want to...	Tool
Drop the first 30s and last 10s of a clip	Video Trim
Remove an awkward middle 5s	Video Cut
Make a horizontal video vertical (or vice versa) by chopping sides	Desktop tool (Shotcut, HandBrake) — Dropvert doesn't surface a frame-crop filter in v1
Shrink the whole frame to a smaller resolution	Video Compress — Resolution: 1080p / 720p / 480p

FAQ

Why doesn't trim let me drop the first 0.5 seconds? Most video files have keyframes every 1-2 seconds; the trim has to land on one. Dropvert's tool snaps to the nearest keyframe by default. If you absolutely need sub-second precision, the tool can re-encode — but a 5-minute trim that previously took 3 seconds takes 5 minutes when re-encoding kicks in. The trade-off is usually not worth it for a 0.5s shift.

Will trimming reduce file size? Yes — proportionally. A 5-minute clip trimmed to 2 minutes is roughly 40% the original size. If you want extra size reduction on top, Compress Video after trimming.

Does the trim work on MKV files? Yes. All of Dropvert's video tools accept MP4, MOV, MKV, WebM, AVI, and most other common formats. The output container can be picked separately (default: match the source).