Compress a video online to the size you need

How a size in MB becomes a bitrate

A video file is mostly its bitrate multiplied by its length. So the tool starts from your size: 25 MB is 25,000,000 bytes, or 200,000,000 bits. Spread over a 2-minute video, that is about 1.67 million bits per second for everything in the file.

From that it takes away the sound (kept as it is when it fits) and the file's index of frames, and keeps 3% spare, because an encoder can run a little over. What is left is the video bitrate, and the picture is encoded at that rate as a constant bitrate, so the file lands just under your number.

When the file is finished, the tool measures it. If it is still over your size, it encodes the video again at a lower bitrate, up to three tries in all, and tells you how many it took.

These are the lengths up to which Auto keeps that picture size at 30 frames per second, with the sound copied at 128 kbps (for 360p, Auto re-encodes it at 96 kbps to leave the picture more room): about 3.1 Mbps of video for 1080p, 1.4 Mbps for 720p, 0.6 Mbps for 480p and 0.35 Mbps for 360p. A longer video still fits, one size down. Fast, detailed scenes such as sport or games show the squeeze sooner than calm ones.

Compress to a size, or by quality

Choose To a file size when there is a limit to meet: an email attachment, a chat app or an upload form. The tool aims just under the number you type and checks the result.

Choose By quality when you only want a smaller file and its exact size does not matter. Each step sets an explicit bitrate for the picture size, and the tool never spends more than the original video does on the same picture:

Sizes per minute include the sound at 128 kbps. By quality uses a variable bitrate, so busy scenes get more and calm ones less, and the final size can differ a little from the estimate. In our tests a 1080p video recorded at 8.7 Mbps came out 53% smaller at Balanced. A video that is already compact may barely shrink, and the tool says so before it starts.

Picture size and frame rate: what Auto does

Squeezing a 1080p picture into too few bits makes it soft and blocky, while the same bits spent on a 720p picture look clean. So with To a file size, Auto picks the biggest standard picture size, never bigger than your video, that still gets at least about 0.05 bits per pixel in every frame.

For videos over 30 frames per second, such as 60 fps game captures or phone clips, Auto tries 30 fps at each picture size before going down a size, because dropping every other frame saves more bits than it costs in smoothness.

If nothing keeps a clean picture, Auto takes the sharpest size that is still watchable and the panel warns you. If the size is far too small for the length, the tool refuses and names the smallest size that works. You can also choose the picture size yourself (any standard size below the video's own, down to 240p, keeping the shape) and, for fast videos, keep the frame rate or use 30 fps.

What happens to the sound

Sound is small next to the picture: 128 kbps is under 1 MB a minute. When the video's sound is AAC or MP3, the formats an MP4 normally holds, and it takes no more than about a fifth of the budget, it is copied exactly, with no re-encoding.

When the size is tight, the sound is re-encoded as AAC at a lower bitrate, down to the lowest your browser's encoder accepts (96 kbps in Chrome on Windows in our tests), to leave room for the picture. Sound in other formats, such as Opus in a WebM or uncompressed PCM in a MOV, is converted to AAC. Tick Remove the sound for a silent video, which gives all the room to the picture.

Common size limits

Gmail lets a personal account attach up to 25 MB in one email, counting all the attachments together; work and school accounts have a limit set by their administrator, and anything bigger becomes a Google Drive link (Gmail Help). Outlook.com and Yahoo Mail also stop at 25 MB. See compress a video to 25 MB for what each one counts, or compress a video for email for sending it.

Discord lets you upload up to 20 MB without Nitro since August 2026, 50 MB with Nitro Basic and up to 1 GB with Nitro, and checks the size of the file you pick before compressing anything (Discord Support). See compress a video for Discord.

GitHub takes videos of up to 10 MB in issues and pull requests when the repository is on a free plan (GitHub Docs), and 10 MB is also classic Outlook's default for an Exchange mailbox. See compress a video to 10 MB.

Limits change, so check the service's own help page. Here 1 MB is 1,000,000 bytes, a little less than the 1,048,576 bytes some apps call a megabyte, so a file made for a limit fits under either count.

Compress a video for WhatsApp or Instagram

WhatsApp's help pages give a default video size limit of 100 MB at 720p on a faster internet connection, and 64 MB at 480p on a slower one. They add that media is usually compressed when shared, and that you can choose Standard or HD quality before you send (WhatsApp Help Center).

So when WhatsApp will not take a video, type 64 here, which is under both limits, and set Picture size to 720p, the most either limit lists. At 64 MB a 720p picture stays clean for about five minutes. Status videos can be at most 90 seconds long and HD is not offered for status for now, so for a status keep only the part you want with Compress only part of the video. To post a longer video whole, WhatsApp status video splits it into parts of up to 90 seconds. WhatsApp's Document option, on the same page, sends files of up to 2 GB.

Instagram asks for reels of at least 720 pixels and 30 frames per second, in a shape between 1.91:1 and 9:16, and that page lists no file size limit (Instagram Help Center). If you compress a reel so it uploads faster, set Picture size to 720p or bigger so the copy stays above that minimum; the tool never lowers a frame rate below 30 fps. Reels can run up to 20 minutes (Instagram Help Center).

Large video files, no size cap

There is no upload, so there is no upload wait and no file size limit from a server. Your browser reads the video from your device a piece at a time instead of loading it whole, so a big recording opens about as quickly as a small one. In our tests a 257 MB one-minute 1080p video opened in under a second and became a 24.2 MB MP4 at 720p in 13 to 14 seconds, in Chrome and in Edge on a laptop.

What takes time is the length, not the file size, because every frame is decoded and encoded again: a long recording takes longer than a short one of the same size. The finished copy waits in memory until you download it, which is no trouble at email or chat sizes. Results over about 500 MB on a computer, or about 200 MB on a phone, go straight into a file you choose where the browser allows it, such as Chrome and Edge on a computer; other browsers keep them in memory, which can fail for very large files.

Compress a video on iPhone or Android

Open this page in your phone's browser and tap the box to pick a video from your photos or files. The work happens on the phone itself, so it takes longer than on a laptop, and the page keeps the screen awake while it encodes where the browser allows it. Stay on the page until it finishes, since a phone can pause a page in the background.

iPhones record in HEVC, the High Efficiency format, unless Settings, Camera, Formats is set to Most Compatible, which records H.264. Apple says HEVC keeps the same picture in less space than H.264 (Apple), so an iPhone video is already compact. The copy made here is H.264, so the real savings come from a size in MB, where Auto also picks a smaller picture, rather than from By quality at full size.

On supported models, iPhones record HDR video, and Apple sends an SDR version to devices that cannot show HDR (Apple). The compressed copy is SDR as well, so its colors and highlights can look a little different. On an iPhone, use Safari 16.4 or later (26 or later when the sound has to be converted); on Android, Chrome or Samsung Internet. Firefox for Android cannot encode video yet.

The MP4 you download goes to Downloads in the Files app on an iPhone (Apple) and to your Downloads on Android (Google), ready to share from there.

What happens to your video

Your browser reads the video from your device in small pieces, decodes each frame, encodes it again and writes the new MP4, all inside this page. The first time you choose a video, your browser downloads the video engine from uncrop.si; your video goes nowhere. Under the download you can see how many requests the page sent while you used it.

The new file carries none of the original's descriptive details, such as a title, the place a phone recorded it or the phone model. The engine would copy those by default (Mediabunny), so the tool writes an empty set instead.

Which videos and browsers work

You can open MP4, MOV, WebM and MKV videos, including iPhone videos in HEVC, the High Efficiency format (Apple). The result is always an MP4 with H.264 video, a format that plays in browsers used by about 97% of people (caniuse). If you need an MP4 but not a smaller file, MKV to MP4 copies the H.264 or HEVC video of an MKV without encoding it again, and WebM to MP4 converts a WebM with no size target.

Compressing decodes and encodes every frame with WebCodecs, which Chrome and Edge have from version 94, Firefox on computers from 130 and Samsung Internet from 17. Safari has it for video from 16.4 and for sound too from 26 (caniuse), so in Safari 16.4 to 18 a video whose sound has to be re-encoded compresses only with the sound removed. Firefox for Android does not have it.

An HEVC video can only be compressed where the browser can decode HEVC: in our tests Chrome on a Windows laptop could and Edge on the same laptop could not. When your browser cannot, the tool says so before anything starts, and the cut video tool still works, because it copies the video without decoding it.

Limits to know

Compressing always loses some detail, because each frame is encoded again with fewer bits. To make a file smaller with no loss at all, keep a shorter part with the cut video tool, which copies the video instead.

It takes time, because every frame is decoded and encoded. On our test laptop a one-minute 1080p video at Balanced took 21 to 34 seconds in Chrome and Edge, and 30 seconds of 1080p at 60 fps kept at full size took almost a minute. Speed depends on your device, and the progress bar shows the time left.

HDR videos from any camera come out in standard range (SDR), so their colors and highlights can look different from the original. The panel tells you when a video is HDR, before you start.