Does Shrinking Video Resolution Stretch or Crop the Frame?

How proportional scaling is actually calculated

Say the original video is 1920×1080 (16:9). Resizing to 1080p by longest edge leaves it unchanged, since 1920×1080 already is 1080p. If the original is 3840×2160 (4K, still 16:9), resizing to 1080p produces 1920×1080 — both width and height are halved, and the ratio stays exactly the same. Resize by ratio works the same way: choosing 1/2 halves both width and height together.

When the aspect ratio might look different than expected

If the original video already has an unusual aspect ratio (a 9:16 portrait phone recording, or a non-standard ratio from certain cameras), that ratio is preserved exactly after resizing — it's never forced into 16:9 or some other "standard" shape. The tool performs an overall shrink and never changes the relationship between width and height.

If a resized video looks like the aspect ratio is off, that's usually not a processing issue but a case where the original file's aspect metadata (rotation metadata from a phone recording, for instance) wasn't preserved correctly somewhere upstream — check whether the original file displays with the correct aspect ratio in other players first.

When you actually need real cropping

If the goal is fitting a landscape video into a portrait frame (converting 16:9 content into something suited to mobile portrait viewing, for example), simply shrinking the resolution doesn't solve that — it requires cropping or adding letterboxing, which changes the framing itself. That's outside what the resize feature here does, and needs a dedicated video editor.

• If the goal is just a smaller file without changing the framing, the built-in resize feature is all that's needed.
• If the aspect ratio or framing genuinely needs to change, handle that composition work in an editor first, then compress the resulting file here.