BuzzKit
Video Compressor
Reduce a video's file size by adjusting the compression quality (CRF) — lower quality numbers mean better looking, larger files.
Lower = better quality, larger file. Higher = smaller file, more compression artifacts.
Uses the H.264 encoder at the CRF value you choose — the standard way video tools trade size for quality.
What this tool is for
A phone records video at whatever bitrate the camera app defaults to, which is usually far more than most videos need. That makes files too big to email, too slow to upload to a group chat, or too large for a website with a strict upload limit. This tool re-encodes a video at a lower bitrate so it takes up less space and moves faster, without desktop software or an upload to a compression service first.
It's aimed at anyone who needs a smaller file rather than a different format: shrinking a phone recording before sending it, getting a video under a platform's size limit, or freeing up storage on a device. If you need to change the container format instead — say, from MOV to MP4 — use Video Converter.
How the video compressor works
This tool re-encodes your video with the H.264 codec at a CRF, or constant rate factor, value you choose — the same lever every professional video encoder exposes. Rather than targeting an exact file size, CRF targets a consistency of quality and lets the file size fall out of that. A lower number preserves more visual detail and produces a larger file; a higher number allows more compression artifacts, such as blockiness in fast motion, in exchange for a smaller file. There's no universally correct value; it depends on the footage and how much reduction you need.
Because the encoder runs as WebAssembly directly in your browser tab, the file is compressed on your own device and never uploaded anywhere. Larger files or older devices need noticeably more time and memory to process, which is why the tool warns before starting if a file looks likely to strain your browser tab.
Common situations this solves
- Getting under a platform's upload limit, such as an email attachment cap or a messaging app's file-size limit.
- Shrinking a phone recording before sending it over a slow connection or mobile data.
- Freeing up device storage by compressing old recordings you want to keep but don't need at full bitrate.
- Preparing a video for a web page, where a smaller file means a faster-loading site.
Limitations, honestly
Compression is genuinely lossy: pushing the CRF value higher to shrink the file further will eventually show up as visible artifacts, especially in fast motion or highly detailed footage. There's no way to target an exact output size directly — you adjust the slider, compress, check the result, and re-run if it's not close enough. The output is always MP4 with H.264, so if you need the original container or codec preserved, this isn't the right tool. And because the process runs in your browser, a long or high-resolution video takes real time and can strain memory on an older phone or low-RAM laptop.
Frequently asked questions
What does CRF mean?
It's the quality dial ffmpeg's H.264 encoder uses — lower numbers preserve more detail at a larger file size.
Will this change the format?
The output is always MP4 (H.264), regardless of the input container.
Is there a target file size option?
Not directly — adjust the CRF slider and re-run until the size suits you.
How long does compression take?
It depends on the video's length, resolution, and your device — a short clip on a modern laptop can finish in seconds, while a long, high-resolution video on an older phone may take several minutes.
Does this work on my phone?
Yes, most mobile browsers support the WebAssembly encoder this tool uses, though very large files may run slowly or hit memory limits on older devices.
Will the audio track be affected?
Audio is carried through with the video and isn't targeted by the CRF setting, so its quality stays close to the original.