Pick the right dimensions for the platform
- 1080 × 1920 (9:16) — Instagram Reels, TikTok, YouTube Shorts, Snapchat. Always the safest vertical format.
- 1080 × 1080 (1:1) — Instagram feed and Facebook square posts. Works well on every timeline.
- 1920 × 1080 (16:9) — YouTube landscape, Twitter/X videos, Vimeo, embedded site players.
- 1280 × 720 (16:9) — same shape, lighter file. Good for HTML5 embeds and bandwidth-constrained pages.
Why preserve aspect ratio
Turning the aspect-ratio lock off will stretch the source frame to fill the new dimensions — heads get squashed or distorted. With the lock on, the resizer scales the video to fit one dimension and adds clean black bars (letterbox or pillarbox) on the other axis. The output retains the original proportions and looks correct on every player.
About the re-encode
Resizing inherently requires a full re-encode — the pixel grid changes, so the H.264 codec has to recompute every frame. The default quality (CRF 23) is visually transparent for most footage. Long source videos take longer to resize than to merely trim or mute; budget roughly half the runtime of the video on a modern laptop.