Resize Video

Scale a video to a standard height or a size you type, and decide what happens when the shape does not match.

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What this tool does

Resize Video hands your clip to ffmpeg on the OmniKitly processing service and rebuilds every frame at the size you asked for. The five presets — 2160p, 1440p, 1080p, 720p and 480p — set the height, and the width is derived from the frame size ffprobe reads off the video stream rather than assumed, so a 4:3 recording taken down to 720p comes back 4:3 instead of being jammed into widescreen. Both figures are then rounded down to an even number, because the H.264 encoder will not accept odd dimensions.

Custom size replaces the preset with two boxes, anything from 16 pixels up to 7680 wide and 4320 tall, and it is where the fit setting does most of its work. Letterbox with bars scales the picture until it fits inside your frame and fills the remainder with black, centred. Crop to fill scales until it covers the frame and cuts the overflow from the edges. Stretch distorts the image to your two numbers and nothing else. A preset has already inherited the stored proportions, so on a file whose orientation is baked into its pixels the three options land within a pixel of one another and the control is close to inert — the exception is the rotation case described next, where the choice is very visible indeed.

One rough edge is worth knowing before you feed it a phone recording. Most handsets record landscape frames and mark the file with a rotation flag rather than storing the picture upright, and the preset path measures the stored frame without consulting that flag while ffmpeg does honour it before scaling. A portrait iPhone clip therefore reports itself as 1920 by 1080, asks for a 1280 by 720 target, and comes back as a wide frame with the tall picture standing in a strip down the middle between two black bars. Choosing crop to fill instead fills the frame but shaves the top and bottom; a custom 1080 by 1920 sidesteps the arithmetic altogether. This is the tool getting it wrong, not your file.

Three things it does not do. The output is always MP4 carrying H.264 video and AAC audio, whatever went in, so an MKV or WebM file is rewrapped as well as scaled and there is no output format picker here — Convert Video is where a container is chosen. The encode also runs at a single fixed constant-quality level, the same middle setting Compress Video labels Balanced, so this tool decides the frame size and gives you no hold over the bitrate. And nothing prevents you scaling upward: ask for 2160p from a 720p source and the scaler will interpolate a 4K frame carrying exactly the detail the 720p original had, in a considerably larger file. Downscaling is the job this does well. The frame rate is left alone on every route.

The work runs on the processing service rather than in the tab, because no browser ships a video encoder that could do this without ruining the picture. Your video travels there over an encrypted connection and is scaled on a machine running ffmpeg. The copy you uploaded is erased the moment the job succeeds, before you have even fetched the result; a job that fails leaves its input in place until the retention window closes, and a sweep every ten minutes clears that along with the finished MP4. The window is six hours unless an administrator has shortened it. Each file may be up to 200 MB, each job is allowed ten minutes of processing, and a clip longer than three hours is turned away at the inspection stage before any encoding begins.

How to use it

  1. Add the video. The 200 MB ceiling applies to each file on its own. Drop in several and every one is scaled as a job of its own under the settings you picked, coming back as a separate download.
  2. Choose the size. 2160p, 1440p, 1080p, 720p or 480p fixes the height and keeps your footage's proportions. Custom size takes an exact width and height instead.
  3. Say what happens when the shape differs. Letterbox with bars, crop to fill, or stretch. It bites on a custom size whose ratio is not the ratio of the source, and on any clip that carries a rotation flag; on everything else the three choices come out the same.
  4. Run it and take the MP4. The result is named after your file with -scale and the .mp4 extension appended, so it will not collide with the original in your downloads folder.

Processing & privacy

Secure server processing. This operation requires temporary server processing.

Common use cases

Cutting a 4K recording down for the web

Camera and screen-capture footage at 2160p is far more than a page needs. 1080p still looks sharp on a laptop and removes most of the weight.

Meeting a limit stated as a resolution

Some submission portals and learning platforms name 720p rather than a number of megabytes. The preset delivers exactly the height they asked for.

Making mixed footage match before an edit

Clips gathered from several phones and cameras drop into one timeline far more easily when every one has already been scaled to a common frame.

Fitting a landscape clip into a vertical frame

A custom 1080 by 1920 with letterboxing keeps the whole picture and pads above and below, instead of cutting people out of the shot.

Questions

Is my video uploaded?
Yes. ffmpeg does the scaling on the processing service, so the clip is sent there over an encrypted connection. The uploaded copy is deleted as soon as the job succeeds, and the MP4 it produced goes when the six-hour retention window closes. Tools that need no upload at all, such as Extract Frames, say so on their own pages.
Why does my portrait phone clip come back with black bars beside it?
Because the preset height is turned into a width using the stored frame size, and the rotation flag that makes the clip portrait is not taken into account — while ffmpeg does apply it when it scales. The picture is never tipped on its side, but it ends up as a narrow strip inside a wide frame. Pick a custom size such as 1080 by 1920, or switch the fit to crop to fill, which covers the frame at the cost of the top and bottom. Footage whose orientation is stored in the pixels themselves is unaffected.
Will resizing distort the picture?
On a custom size it depends on the fit setting: letterbox and crop both keep the shape, and stretch is the one option that deliberately squashes the image to reach your numbers. A preset keeps the proportions read from the video stream, which is right for footage stored the way it is displayed, and wrong for a clip that leans on a rotation flag — see the question above.
Can it make a small video bigger?
It will try, and the result is what interpolation gives you. New pixels are invented between the old ones but no detail is recovered, so a 480p clip taken to 1080p looks like a soft 480p clip in a larger, heavier file. Scaling down is where this tool earns its place.
Does the file always come back as MP4?
Yes. The container is fixed at MP4 with H.264 and AAC, so a WebM, MKV, AVI or MOV source changes format as well as size. Send the result through Convert Video when you need one of the other containers back.
Can I set the quality or the bitrate?
Not on this tool. Every job uses one constant-quality level, equivalent to Compress Video's Balanced tier. When a particular file size or codec is the actual requirement, downscale here first and compress the result second.
Is the audio kept?
Yes, the track is carried through, but it is re-encoded to AAC rather than copied across, so each pass costs a little audio quality. Mute Video is the tool that removes the track entirely.
How big and how long a clip will it take?
Up to 200 MB per file and ten minutes of processing per job, with anything over three hours refused before work starts. A long, high-resolution source is what reaches the time limit; trim it first if a job runs out.

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