How do I resize a video online for free without uploading it?

Choose a video, pick 1080p, 720p, 480p, 360p, 50% or a custom width, then press Resize video. The aspect ratio is preserved automatically and the result downloads as MP4. Everything runs inside the browser tab, so the file never reaches a server.

Do the presets ever upscale a video?

No. Each height preset takes the smaller of your target and the source height, so choosing 1080p on a 480p clip leaves it at 480p rather than stretching it. That is deliberate — upscaling adds file size without adding detail. The custom width field is the exception and will enlarge if you ask it to.

Can I upscale a low-resolution video to 4K?

You can enter a larger custom width, up to 7680 pixels, but understand what you get: interpolated pixels, a much bigger file and no new detail. For genuine enhancement rather than stretching, the AI video upscaler reconstructs detail instead of interpolating it.

Will resizing distort the aspect ratio?

No. Only one dimension is set and the other is derived from it, so 16:9, 9:16, 4:3 and square clips all keep their proportions. Both dimensions are also rounded to even numbers, which H.264 requires — that is why an output width can land a pixel off what you typed.

How much smaller will the file be?

Resolution is the biggest single lever on video file size, and halving the height cuts the pixel count to a quarter, so the savings are usually large. The exact figure depends entirely on your source bitrate and how much motion the footage contains, so treat any percentage as a rough guide.

What does the 50% preset do differently?

It halves both dimensions relative to the source rather than targeting a fixed height, so it works the same way on a 4K clip and a 720p one. Use it when you want a predictable reduction without caring about landing on a standard resolution name.

Is the audio re-encoded too?

Yes. Audio is always re-encoded to AAC at 128 kbps rather than passed through, so it stays in sync with the rescaled video and lands in a codec every player accepts. Video is written as H.264 at CRF 23, a size-focused setting rather than a maximum-quality one.

What formats and file sizes are supported?

MP4, MOV, WebM, AVI and MKV up to 500MB, always exporting MP4. Encoding runs on a single CPU thread with no GPU acceleration, so expect roughly real-time speed, and the engine is about 31MB to download on your first use.

Resize Video

Change a video’s resolution — downscale 4K to 1080p/720p/480p with the aspect ratio preserved, right in your browser.

Files never leave your deviceInstant — no upload waitFree, no sign-up

Choose a video or drag & drop it hereMP4, MOV, WebM… resized on your device, never uploaded

or import from

Resize a video to 1080p, 720p, 480p, 360p, half size or any custom width, with the aspect ratio preserved automatically. Lowering resolution is the most effective way to shrink a video file. Runs entirely in your browser using FFmpeg compiled to WebAssembly — no upload, no sign-up, no watermark, up to 500MB.

The presets, and the one that behaves differently

What each option does to the source.
Option	Behaviour	Can it enlarge?	Use it for
1080p	Caps height at 1080	No	Downscaling 4K while staying sharp on a laptop
720p (default)	Caps height at 720	No	The best size-to-quality balance for sharing
480p	Caps height at 480	No	Email and messaging attachment limits
360p	Caps height at 360	No	Previews, proofs, very tight limits
50%	Halves both dimensions	No	A predictable cut regardless of source size
Custom width	Sets width to 16–7680px exactly	Yes	Hitting a specific platform requirement

The distinction in that third column is the thing to notice. Every height preset takes thesmaller of your target and the source, so picking 1080p on a 480p clip leaves it at 480p instead of stretching it — the tool will not waste bytes inventing pixels. The custom width field has no such guard and will enlarge up to 7680px if you ask, which is occasionally what you want and usually not.

Why resolution beats every other size lever

Pixel count scales with the square of the dimensions, so the arithmetic is dramatic. Going from 1080p to 720p is a modest-sounding change in the name but drops the pixels per frame from about 2.07 million to 0.92 million — roughly 44% of the original. Down to 480p and you are at about 0.41 million, near a fifth. Fewer pixels means less for the encoder to describe, every frame, for the whole clip.

How much the file actually shrinks still depends on your source bitrate and how much motion the footage contains, so treat any single percentage claim with suspicion. The direction is reliable even when the magnitude is not: 720p is the default here because it is the sweet spot — small enough to share comfortably, sharp enough that most people watching on a phone or laptop will not notice the drop.

Resizing, cropping and compressing are three different jobs

Resizing changes the pixel dimensions and keeps all the content. Everything gets smaller.
Cropping keeps the pixel size and removes content from the edges — that is crop video.
Compressing keeps both dimensions and content, and spends fewer bits describing them — that is the video compressor.

They stack, and the order matters for quality. If a file is far too large, resizing first and compressing second usually beats compressing hard at full resolution, because a smaller frame needs fewer bits to look clean in the first place.

What the encode actually produces

Scaling sets one dimension and derives the other, so proportions are always preserved, and both are rounded to even numbers because H.264 requires it — which is why an output can land a pixel away from a round figure. Video is written as H.264 at CRF 23, a deliberately size-focused setting rather than the maximum-quality one used by the rotate and trim tools, andaudio is always re-encoded to AAC at 128 kbps rather than passed through untouched.

Encoding runs on a single CPU thread with no GPU acceleration, since the site does not set the cross-origin isolation headers the multi-threaded build requires. Expect roughly real-time speed, a~31MB engine download on first use, and keep the tab in the foreground so the browser does not throttle it.

How this compares to the alternatives

Resizing one clip, three ways.
	ToolJiffy	Typical online resizer	Desktop software
Video uploaded to a server	No	Yes	No
Sign-up	No	Often to export	Install or licence
File-size limit	500MB	Commonly capped free	None practical
Watermark	Never	Common on free tiers	No
Refuses to upscale by preset	Yes — deliberately	Rarely	Your choice
Speed	Single CPU thread, no GPU	Fast, server-side	Fastest, all cores
Price	Free, unlimited	Free tier then paid	Free to paid

Frequently Asked Questions

How do I resize a video online for free without uploading it?
Choose a video, pick 1080p, 720p, 480p, 360p, 50% or a custom width, then press Resize video. The aspect ratio is preserved automatically and the result downloads as MP4. Everything runs inside the browser tab, so the file never reaches a server.
Do the presets ever upscale a video?
No. Each height preset takes the smaller of your target and the source height, so choosing 1080p on a 480p clip leaves it at 480p rather than stretching it. That is deliberate — upscaling adds file size without adding detail. The custom width field is the exception and will enlarge if you ask it to.
Can I upscale a low-resolution video to 4K?
You can enter a larger custom width, up to 7680 pixels, but understand what you get: interpolated pixels, a much bigger file and no new detail. For genuine enhancement rather than stretching, the AI video upscaler reconstructs detail instead of interpolating it.
Will resizing distort the aspect ratio?
No. Only one dimension is set and the other is derived from it, so 16:9, 9:16, 4:3 and square clips all keep their proportions. Both dimensions are also rounded to even numbers, which H.264 requires — that is why an output width can land a pixel off what you typed.
How much smaller will the file be?
Resolution is the biggest single lever on video file size, and halving the height cuts the pixel count to a quarter, so the savings are usually large. The exact figure depends entirely on your source bitrate and how much motion the footage contains, so treat any percentage as a rough guide.
What does the 50% preset do differently?
It halves both dimensions relative to the source rather than targeting a fixed height, so it works the same way on a 4K clip and a 720p one. Use it when you want a predictable reduction without caring about landing on a standard resolution name.
Is the audio re-encoded too?
Yes. Audio is always re-encoded to AAC at 128 kbps rather than passed through, so it stays in sync with the rescaled video and lands in a codec every player accepts. Video is written as H.264 at CRF 23, a size-focused setting rather than a maximum-quality one.
What formats and file sizes are supported?
MP4, MOV, WebM, AVI and MKV up to 500MB, always exporting MP4. Encoding runs on a single CPU thread with no GPU acceleration, so expect roughly real-time speed, and the engine is about 31MB to download on your first use.