How to compress a video online
Video too big to email, attach or upload? Here is how to shrink a video's file size right in your browser — pick a quality, keep the audio, and download a smaller MP4, with nothing uploaded to anyone.
A phone or screen recording can easily be hundreds of megabytes — too large for an email attachment, a messaging app's limit, or a slow upload. Compressing re-encodes the video at a lower bitrate (and, if you choose, a smaller resolution), which cuts the file size dramatically while keeping it perfectly watchable. The Video Compressor does this locally, so your clip is never sent to a server.
Before you start
- Formats in: MP4, MOV and WebM load reliably, using your browser's own decoder.
- Format out: a smaller MP4 (H.264) with the audio kept — the format upload and messaging services expect.
- It is a re-encode. Compression works by trading away a little detail for a much smaller file, so it is not a lossless copy. You choose how far to go.
- It runs in real time, on your device. Expect it to take roughly as long as the clip plays, and keep the tab in the foreground while it works.
- Size is limited by your browser's memory, not an upload cap. Nothing is uploaded, but a very large source needs enough memory to decode and re-encode — more on a desktop, less on a phone.
Compress a video in 3 steps
- Open the compressor and drop your video in. Go to the Video Compressor and choose or drag an MP4, MOV or WebM. It loads locally and shows the current size and dimensions.
- Choose how much to compress. Pick a quality level (and a smaller resolution if you want an even smaller file). Higher quality keeps more detail for a bigger file; lower quality saves more space. For most sharing, a medium setting is the sweet spot.
- Compress and download. Start it, wait while it re-encodes on your device, and save the smaller MP4 when it finishes. The audio comes along automatically.
What makes a video file big?
Three things drive size, and knowing them helps you predict the result. Bitrate — how much data the video uses per second — is the biggest lever, and it is exactly what the quality setting changes. Resolution (1080p, 720p, 480p) sets the pixel count; halving it roughly quarters the raw data. Length multiplies both. A fourth factor is the source codec: footage straight off a phone or a screen recorder is usually only lightly compressed, which is why it shrinks so much, while a video that has already been squeezed hard has less left to give. So to go small, lower the quality first, and only drop the resolution if you still need more.
Best settings for common jobs
Emailing or messaging a clip
Aim for the smallest size that still looks acceptable. A medium-to-low quality at 720p usually clears typical 25 MB email limits for short clips; drop to 480p for longer ones.
Uploading to social or a form with a size cap
Keep the resolution the platform recommends and lower the quality until you are under the cap. Most platforms re-compress anyway, so there is little point uploading a huge file.
Keeping it watchable on a big screen
Stay at the source resolution and use a higher quality setting — you will still save space versus the original without an obvious drop.
Troubleshooting
- The file barely got smaller. The source may already be efficiently compressed. Lower the quality further, or reduce the resolution for a real drop.
- It looks too soft. You compressed too hard — redo it one quality step higher, or keep the original resolution.
- It is slow or ran out of memory. Real-time re-encoding tracks the clip length; a very long or very large source is heavier. Try trimming it first with the Video Cutter, or compress on a desktop.
- Only part needs to be small. Cut the section you need first, then compress just that — a shorter clip compresses faster and smaller.
Is it private?
Yes. The whole process — decode, re-encode, download — happens in your browser. Your video is never uploaded, there is no account, and there is no watermark on the output.
Quality and format notes
Compression is inherently lossy: a smaller file always means slightly less detail. The output is standard MP4/H.264 for maximum compatibility. If you specifically need different dimensions rather than a smaller file, use Resize Video; to keep only part of the frame, use Crop Video.
Related TrackMix tools
To change the dimensions instead of the file size, use Resize Video. To convert a MOV to MP4 or WebM to MP4 without much size change, use the converters. To shorten the clip first, use the Video Cutter.
Frequently asked questions
Is it free and private?
Yes. It is free with no sign-up or watermark, and the video is compressed in your browser, so it is never uploaded to a server.
How small can it make my video?
It depends on the source and the quality you pick. Lowering the quality and, if needed, the resolution gives the biggest savings — screen recordings and phone clips often drop a lot, while already-compressed video shrinks less.
Will compressing lose quality?
Some, yes — smaller files always trade away a little detail, and this is a re-encode rather than a lossless copy. A higher-quality setting keeps more detail for a larger file; a lower one saves more space. Pick the balance you need.
Does it keep the audio?
Yes — the audio track is kept in the compressed MP4.
Which format does it output?
MP4 (H.264), which plays almost everywhere and is what most upload and messaging services expect.