Compress Video — Reduce MP4 File Size

How to use it#

Drop a video onto the box above, or click it to choose one.
Choose Quality and pick Smaller, Balanced, or Better, or choose Target size and type the limit the video has to fit under.
Pick a resolution. 1080p suits most sharing, and 720p makes the file smaller again.
To keep only part of the video, set the start and end, typed or taken from the preview with Set from video.
The video is compressed as soon as a setting changes. Check the new size and the preview, then download the MP4.

Where the size of a video goes#

A video file is its bitrate multiplied by its length. A phone records at a high bitrate so the picture holds up however it is edited later: a minute of 1080p from an iPhone is usually 60 to 130 MB, and a minute of 4K several times that. Nobody watching on a phone or a laptop can see most of that detail, which is why a video can often lose most of its size with no visible change.

Compressing re-encodes every frame at a lower bitrate, and usually at a lower resolution too. Resolution is the bigger lever: 1080p has a quarter of the pixels of 4K, so it needs far fewer bits for the same sharpness on screen. Keeping 4K and cutting the bitrate instead makes a blocky 4K video that looks worse than a clean 1080p one of the same size.

By quality, or to fit a size#

Quality sets how many bits each frame gets for its size. Balanced gives 1080p about 5 Mbit/s, which looks clean for most footage. Smaller roughly halves that, for sending a clip where the size matters more than fine detail, and Better gives more for footage with fast movement, water, or foliage, which compress worst. Whichever you pick, the video never gets more than 70 per cent of the bitrate the original had, so a video already recorded small still comes out smaller.

Target size works the other way round. It takes the limit you type, subtracts room for the sound, and spreads the rest across the length of the video, aiming a little under the limit so the finished file fits. A long video squeezed into a small limit gets few bits per frame, so pair a small target with 720p or 480p, or cut the video shorter: the size is worked out from the part you keep, so half the length gets twice the bits per frame. When a limit is out of reach, the page says how small the video can go instead.

What stays the same#

AAC or MP3 sound, which is what phones record, is copied across without being re-encoded, so it loses nothing. The frame rate stays the same, and so does the length unless you set a start or an end, and a portrait video stays portrait. The date, place, and device the original recorded are copied too; the video metadata viewer shows them and can make a copy without them.

The result is always an H.264 MP4, the one format every phone, computer, and website plays. That also makes this the way to turn an iPhone HEVC video, or a WebM, into something that plays everywhere. If you only need the format changed and not the size, MOV to MP4 copies an iPhone video into an MP4 with no loss.

Frequently asked questions#

How much smaller will my video get?

It depends on how it was recorded. A phone video brought down from 4K to 1080p at Balanced often ends up a tenth of its size, and a 1080p one a quarter to a half. The Result and Change figures beside the video show the real size, measured from the compressed file, before you download it.

How do I compress a video to a certain size?

Choose Target size under Compress by, then type the limit in megabytes, or press one of the presets. For an email attachment or a chat app, type the limit it gives. The video is fitted a little under it. If the video is too long for the limit, the page says the smallest it can go, and a lower resolution makes a small limit look better.

What size should I aim for to send a video by email or in a chat app?

Whatever limit the app or email service gives. Some email services take attachments of up to about 25 MB, and some chat apps allow as little as 10 MB, which is why those two are among the presets. Limits change, so check the one you are sending to and type it in. A clip squeezed into a small limit looks better at 720p or 480p than at 1080p.

Can I compress a video without losing quality?

Not strictly. A smaller file means encoding the video again with fewer bits, and some detail goes each time. What goes can be detail nobody sees, though: a phone video taken from 4K to 1080p at Better usually looks the same on a phone or a laptop at a fraction of the size. Compress once, from the original, because each round adds its own loss.

Can I cut the video while compressing it?

Yes. Set the start and the end, and only that part is compressed. A size target is then spread over the part you keep, so a shorter clip looks better under the same limit. To cut a video and keep its format and quality, use trim video.

What does changing the quality do?

It sets the bitrate, the number of bits the video gets for each second, and the file size follows it: the result is roughly its bitrate times its length. For 1080p at 30 frames a second, Smaller gives about 2.8 Mbit/s, or about 20 MB a minute, Balanced about 5 Mbit/s, or 40 MB a minute, and Better about 8 Mbit/s, or 60 MB a minute. A lower resolution needs fewer bits and brings all three down, and 60 frames a second doubles them. Fewer bits means less detail kept: at Smaller, grass, hair, and water go soft, and fast movement and dark scenes can break into blocks. The resolution, frame rate, length, and sound are the same at every setting. No setting goes above 70 per cent of the bitrate the original had, so a video recorded at a low bitrate can come out the same at Balanced and Better. Balanced suits most videos; Smaller suits a clip sent in a message, and Better footage you are keeping or with a lot of fast movement.

Which resolution should I pick?

1080p for anything watched full screen, 720p for sharing, where it looks sharp on a phone and saves a lot more, and 480p when the size matters most. Original keeps the resolution and only lowers the bitrate. A video is never scaled up, so 1080p leaves a 720p video as it is.

Why can I not download the compressed video?

Because it came out no smaller than the original. The bitrate is always set below the original's, but a video that was already compressed very hard can still end up the same size. Try Smaller, a lower resolution, or a target size under the current one.

Does compressing change the sound?

No. The sound is copied into the MP4 as it was. The one exception is sound an MP4 player may not expect, such as the Opus sound in a WebM, which is converted to AAC where your browser can make it.

Why is it slow?

Compressing means encoding every frame of the video again, the heaviest job a video tool does. Your file never leaves your device, so the work is done by your own computer or phone, inside this browser tab, not on a server built for it. Every frame is decoded and compressed again: a minute of 1080p at 30 frames a second is 1,800 pictures of about two million pixels each, and 4K has four times as many pixels. The browser hands the compression to your device's video chip where it has one, but each frame still passes through the tab, which shares the processor with everything else that is open. A phone also slows itself down as it warms up, and some browsers slow a tab you switch away from, so keeping this tab in front, closing other tabs, and plugging a phone in all help.

Is my video uploaded?

No. The video is read, compressed, and handed back inside this browser tab, so a personal video stays on your device the whole time.