Every social media platform has preferred video dimensions, and uploading the wrong size means your content gets cropped, letterboxed, or compressed poorly. The platforms will accept almost any input and force it into their format, but the results are usually worse than if you resize it yourself beforehand.
Platform dimensions at a glance
TikTok prefers 1080x1920 (9:16 vertical). YouTube prefers 1920x1080 (16:9 horizontal) for standard videos and 1080x1920 (9:16) for Shorts. Instagram Reels uses 1080x1920 (9:16). Instagram feed posts use 1080x1080 (1:1 square) or 1080x1350 (4:5 portrait). Facebook supports 1280x720 or 1920x1080 for landscape and 1080x1920 for Stories.
If you record everything at 1920x1080 (standard landscape), you already have the right dimensions for YouTube and Facebook. For vertical platforms like TikTok and Reels, you need to either crop the landscape video to vertical or resize for a vertical frame (which may require letterboxing).
Resizing versus cropping
Resizing changes the dimensions of the entire video frame. If you resize a 1920x1080 video to 1080x1080, every pixel gets scaled. This can look stretched or squeezed if the aspect ratio changes.
Cropping removes edges and keeps a section at full resolution. If you crop a 1920x1080 video to 1080x1080, you cut away the left and right sides. The center stays sharp.
For converting horizontal to vertical, cropping usually looks better because you keep full resolution on the content that matters. The trade-off is that you lose the edges of the frame. If important content is at the edges, resizing with padding (black bars or a blurred background) might be more appropriate.
Downscaling is safe, upscaling is not
Resizing from a larger resolution to a smaller one (downscaling) is always fine. You are discarding pixels, and the output is sharp. Resizing from a smaller resolution to a larger one (upscaling) stretches the existing pixels, creating a soft or blurry result. If your source is 720p, resizing it to 1080p does not add detail; it just makes the file larger and softer.
The practical rule: always export from your source at the highest resolution available, then downscale for each platform as needed.
How to resize a video in your browser
The MediaBrew resize tool includes presets for every major platform: TikTok (1080x1920), YouTube (1920x1080), Instagram Square (1080x1080), and others. Upload your video, pick a preset or enter custom dimensions, and download the resized file. Processing runs entirely in your browser using FFmpeg WebAssembly. No upload, no account, no watermark.
For batch workflows where you need the same video in multiple sizes, you can upload once and run the resize tool multiple times with different presets.