Resize a video without uploading it

The same presets applied to a portrait phone clip recorded at 1080×1920 behave the other way round: 9:16 is a no-op, 16:9 crops a 1080×608 strip from the middle (or letterboxes it with bars at the sides in Fit mode), and 720p gives 720×1280, because the presets scale by the short side.

A video has the detail its camera recorded and no more. Scaling 720p up to 1080p makes the file larger and the picture softer, because the encoder has to spend bits describing pixels that are interpolated, not real. Platforms then scale it back down for most viewers anyway. So ClipHeron never upscales unless you tick Allow upscaling: on the 1080p preset a 720p source stays 1280×720, and the aspect presets shrink their canvas to match a small source rather than stretch it.

There is one honest exception. Some platforms treat a vertical video under 1080 px wide as low quality and compress it harder, and some old TVs and projectors refuse anything that is not a standard size. If you know the destination needs the exact preset size, allow upscaling and the preset size is produced regardless of the source.

Fit is the safe choice when the action is spread across the frame, when there is text or a caption near the edges, or when you are turning a landscape clip into a vertical one for a story. Black bars are neutral; blurred bars (a soft, darkened copy of the same frame) look like what the Instagram and TikTok apps produce and hide the letterbox at a glance.

Crop is better when the subject is in one place: a talking head, a product on a table, a screen recording where only the middle matters. The crop keeps the centre by default and you can drag the frame along the free axis on the preview, or focus it and use the arrow keys (Shift for bigger steps). The crop position applies to the whole clip, so if the subject moves, Fit is the safer bet.

Whichever you pick, the output size is snapped to the exact ratio with even dimensions, because H.264 encoders need even numbers and platforms check the ratio, not just the size.

Resizing always re-encodes the video, because the pixels change. ClipHeron encodes at its Best preset for the output size, which is a bitrate ladder by resolution and frame rate (about 7 Mbps for 1080p30, 3.5 Mbps for 720p30), so a downscale usually ends up both smaller and visibly as good as the source. Your device’s hardware encoder is used through WebCodecs where the browser offers it, which is what makes a 1080p clip resize at several times real time on a laptop; the file card names the encoder in use.

If a size limit is the real goal, resize first and then run the result through the compressor, which lets you name a target in megabytes. Audio is never touched by this tool: AAC is copied byte for byte, and anything else is converted to AAC once.

Processed on your device. Your video is never uploaded. ClipHeron runs in your browser. We don’t receive your videos, their names or anything in them. Ads on this page load separately and are not given your files.

Decoding, scaling, cropping and encoding run in your browser: frames go from the decoder to a canvas to the encoder in memory, a few at a time, and the MP4 is assembled in the browser’s private temporary storage before it is handed to the download. Nothing about the file, its name or its frames is sent anywhere or remembered.

The page does load advertising and analytics scripts, separate from the tool and described in our privacy policy. They are never given your files.

• YouTube Help: recommended upload encoding settings
• MDN: WebCodecs API
• ISO/IEC 14496-12: ISO base media file format (track header matrix)

Page reviewed October 24, 2026 by the ClipHeron team · How it works · Changelog · Report a problem