Resize Video Online
Set precise video dimensions or fit the source inside a common landscape, vertical, or square frame. Your video stays on your device.
Why resize a video in your browser?
- Keeps the source aspect ratio locked by default to prevent stretching
- Includes 1080p, 720p, vertical, and square fit presets
- Starts at the source size without enlarging smaller videos automatically
- Normalizes output width and height to even numbers required by compatible H.264
- Exports H.264 and yuv420p MP4 video with optional AAC audio
- Processes the source locally in your browser without an upload or watermark
Frequently asked questions
What does the aspect-ratio lock do?
When the lock is on, changing width recalculates height from the source ratio, and changing height recalculates width. This avoids stretching. Turn it off only when you intentionally need exact dimensions with a different ratio.
How do the vertical and square presets work?
They fit the entire source inside a 1080 × 1920 vertical or 1080 × 1080 square boundary without cropping, padding, or stretching. A landscape source therefore remains landscape; use a crop or canvas tool when you need to fill a different aspect ratio.
Will this tool enlarge a small video?
Not on initial load. The default dimensions stay at or below the source size. Choosing a larger preset or manually entering larger dimensions is an explicit request to upscale, which can increase file size without creating new detail.
Why are odd dimensions adjusted?
The broadly compatible yuv420p pixel format requires even width and height. Odd values are rounded down to the nearest valid even pixel so H.264 players can decode the result reliably.
Does resizing change video quality or file size?
Yes. The video is re-encoded with lossy H.264 compression. Reducing dimensions often lowers file size, while enlarging can create a larger file without adding real detail. Motion, source bitrate, and audio also affect the result.
What is preserved in the resized MP4?
The first video track is resized, and the first audio track can be converted to AAC. Subtitles, chapters, location data, cover art, and other metadata are not copied. Processing runs locally in your browser.
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