Why change a video's resolution?
Lowering the resolution is useful more often than you might think:
- To make a 4K phone video manageable: 4K holds four times the pixels of 1080p and is far bigger than needed for phones, laptops or social media.
- To meet an upload rule: some forms, LMS platforms and older apps accept only up to 1080p or 720p.
- To play on older hardware: some TVs, car screens, projectors and budget tablets can't decode 4K, or play it with stutter.
- To make editing smoother: lower-resolution copies, often called proxies, are much lighter to scrub through on an older computer.
What do 1080p, 720p and 480p mean?
Video resolutions are named after the shorter side: 1080p means 1080 pixels on the short side. This tool works the same way, so it does the right thing for both orientations. A landscape 3840×2160 video at 1080p becomes 1920×1080, and a portrait 2160×3840 phone video becomes 1080×1920. The aspect ratio is always kept, so nothing is stretched.
Videos already smaller than the size you pick are never scaled up. Upscaling adds pixels without adding detail, so it would only make the file bigger. Dimensions are rounded to even numbers, which the H.264 encoder requires.
Which resolution should I pick?
Pick the smallest resolution that still looks right where the video will be watched:
- 1080p (Full HD): the standard for sharing, YouTube and laptop or TV viewing. It's the sensible target for 4K phone footage.
- 720p (HD): looks fine on phones and in chat apps, and is roughly half the file size of 1080p. WhatsApp, Telegram and many email clients show video at about this size anyway.
- 480p (SD): for very small files, slow connections, or archiving long recordings where detail doesn't matter, such as lectures and meetings.
- 360p: the smallest option, for previews and thumbnails, or squeezing a long video under a strict size limit.
Resize or compress?
Both make files smaller, in different ways. Resizing reduces the number of pixels; the encoder then needs fewer bits for the same quality per pixel. Compressing (in the Video Compressor) chooses both resolution and how hard to squeeze for you.
Use Resize when you need a specific resolution, because a platform or device demands 720p for instance. Use the Compressor when what you really need is a smaller file and you don't mind how it gets there.
Quality, sound and privacy
The resized video is encoded as H.264 MP4 at CRF 23, a high-quality setting where the main visible change is the lower resolution itself. Scaling down from 4K to 1080p often looks cleaner than footage shot at 1080p, because the downscale averages out sensor noise. The audio is kept and stays in sync.
Everything runs in your browser with ffmpeg compiled to WebAssembly. The file stays on your device. There's no upload and no watermark, and no file size limit apart from what your device's memory can handle.
How much smaller does a resized video get?
File size falls roughly in line with the number of pixels. Going from 4K (about 8.3 million pixels per frame) to 1080p (about 2.1 million) leaves a quarter of the pixels, and the H.264 encoder needs correspondingly fewer bits. Combined with re-encoding iPhone or Android footage at a sensible quality, a 4K clip often ends up 85–95% smaller at 1080p, and smaller still at 720p.
To avoid resizing in future, set the recording resolution on the phone itself. On iPhone, go to Settings → Camera → Record Video and choose 1080p. On Android, the resolution is usually in the camera app's video settings. 4K is worth keeping for footage you plan to edit, crop or zoom into; for everyday clips, 1080p is plenty.