Phone videos are recorded at high bitrates so the camera never runs out of headroom. That makes them far bigger than they need to be for sharing. Compressing well comes down to three levers.
1. Use an efficient codec
H.264 is the safe universal choice. HEVC (H.265) and AV1 reach the same quality with 30–50% less data, but not every device plays them. Spool's compressor outputs H.264 MP4 by default, or VP9 WebM for websites.
2. Lower the resolution when the screen is small
A 4K video watched on a phone or in a chat app is wasted data. Dropping from 2160p to 1080p cuts the pixel count by 75%; 720p is fine for messaging apps and email.
3. Let the encoder pick the bitrate (CRF)
Instead of a fixed bitrate, a constant rate factor (CRF) tells the encoder to keep quality constant and spend bits only where the image needs them — fewer on a static talking head, more on confetti. Our "Light", "Recommended" and "Strong" levels map to CRF 24, 28 and 32.
When you need an exact size
Discord (10 MB on the free plan), email (around 20–25 MB) and some upload forms have hard limits. Switch the method to Target size and type the number of megabytes. We calculate the bitrate from your video's length, encode, and if the result overshoots we re-encode once more with a corrected bitrate. Very long videos may need a lower resolution to look good at small sizes: as a rule of thumb, 10 MB holds about 1 minute of decent 720p.
What not to do
- Don't compress the same file repeatedly — each pass adds artifacts. Always start from the original.
- Don't "zip" videos to save space; video is already compressed and zipping saves almost nothing.
Try it: compress a video, or go straight to compress for Discord.