Resize video online

Resolution affects more than visual quality: it directly controls file size, upload time, processing speed in editing software, and whether a video meets a platform's dimensional requirements. TikTok and Instagram Reels require 9:16 vertical video. YouTube thumbnails and embeds are sized for 16:9. A video shot at 4K on a mirrorless camera is 4 to 6 times larger than the 1080p version a social platform will actually display.

Downsizing to the delivery resolution before uploading also avoids the double-compression problem: if you upload a 4K video to a platform that encodes it to 1080p, the platform's encoder runs on top of your encoder's work. Exporting at 1080p and uploading that directly typically produces a cleaner result.

For resolution presets, the tool uses scale=-2:H where H is the target height (2160, 1080, 720, 480, or 360). The -2 on the width tells FFmpeg to compute the width automatically while keeping it divisible by 2 (required by H.264). This preserves the original aspect ratio exactly without any cropping or letterboxing.

For platform presets that require a specific aspect ratio (TikTok, Instagram Reels at 1080x1920, Instagram Square at 1080x1080), the filter becomes scale=W:H:force_original_aspect_ratio=increase,crop=W:H. This first scales the video up until both dimensions meet the target, then crops the excess from the center. The tool warns you when a platform preset will crop your video. For custom width input, the tool rounds to the nearest even number before passing to FFmpeg. All outputs use libx264 at CRF 23 with the ultrafast preset and AAC audio at 128 Kbps.

Resizing up (upscaling) does not add detail: it just interpolates pixels that were never captured. If your source is 720p and you resize to 1080p, the output will be a blurry 1080p, not a sharp one. Only downscale unless the destination platform requires a minimum resolution.

For the platform presets that crop, compose your shot with the crop in mind. Vertical (9:16) presets cut roughly 44 percent of the width from a standard 16:9 landscape video. Subjects near the left or right edges of the frame will be lost.

Platform-specific export presets are a standard feature of desktop editors, but they require a project setup. FFmpeg can resize with a single command, but computing the exact scale and crop arguments for a specific platform aspect ratio (and remembering to keep dimensions even) requires looking up the math every time. This tool has the correct vf arguments for each platform preset built in and runs them locally with no setup.