Compress a video without uploading it
Reduce a video to a fraction of its size for email, WhatsApp, Discord or a website. Choose a quality level (CRF) and optionally a maximum width; the tool re-encodes with H.264 and AAC on your device and shows the before/after size.
How to use the Video Compressor
- Drop a video.
- Pick a quality: CRF 28 with 720p suits most sharing; CRF 23 keeps quality for archiving.
- Click Compress and wait; progress shows during encoding.
- Compare the sizes shown, then download.
What actually makes video files big
Phone cameras record at very high bitrates (an iPhone 4K clip is about 50 MB per minute) because they optimise for editing, not sharing. Almost all of that data is invisible on a phone or laptop screen. Re-encoding with H.264 at a sensible quality removes it: a typical 1080p phone video shrinks by 70–85% at CRF 28 with no visible difference on a screen, and a 4K video downscaled to 1080p shrinks by more than 90%.
CRF explained
CRF (constant rate factor) tells the encoder how much quality to keep, from 0 (lossless) to 51 (unwatchable). Each step of 6 roughly halves the file size. 18–23 is visually lossless, 26–28 is the sweet spot for sharing, 32+ is for previews and very tight limits. Unlike a bitrate target, CRF spends bits where the picture needs them, so static scenes get tiny and action stays clear.
Typical limits to hit
| Destination | Limit | Suggested setting |
|---|---|---|
| 64 MB (16 MB on older versions) | 720p, CRF 28 | |
| Discord (free) | 10 MB (25 MB Nitro basic) | 720p, CRF 32, 64 kbps audio |
| Gmail attachment | 25 MB | 720p, CRF 30 |
| Website background | < 5 MB ideal | 1280 px, CRF 32, muted |
How it runs without uploading
This tool uses ffmpeg, the same open-source engine behind most video software, compiled to WebAssembly. The first time you use a video tool the engine (about 30 MB) is downloaded from a content delivery network and cached by your browser; after that it loads instantly, even offline. Your video is read into memory, processed by the engine inside the browser sandbox, and the result is offered as a download. Nothing is transmitted. Because it runs on one CPU core, encoding takes roughly real time to three times real time depending on your device: a 30-second clip takes 30–90 seconds, a 10-minute video may take 10–30 minutes and needs a few hundred megabytes of free memory. For long videos, trim first or use a desktop tool.
Frequently asked questions
Will the compressed video lose quality?
At CRF 23–28 the difference is not visible on phones or laptops. Very low quality settings show blockiness in fast motion.
What is the maximum file size?
There is no fixed cap, but the whole file must fit in browser memory; files up to roughly 1–2 GB work on a desktop, less on phones.
Does it keep the audio?
Yes, re-encoded as AAC at the bitrate you choose. Use the mute tool to remove it.
Is the video uploaded?
No. Encoding happens in your browser.
Privacy
This tool runs entirely inside your browser using WebAssembly and the Canvas/File APIs. Your files are never uploaded to ToolFlint or any third party; you can verify this in your browser's network tab or by switching to airplane mode after the page loads. Read how we process files.
Last updated 2026-09-23.