Video Compression Basics: Bitrate, Resolution, and Encoding Explained

Video files are large for three main reasons: resolution, bitrate, and codec. Understand how these three interact, and you'll know exactly which trade-offs to make when compressing.

Bitrate: Where File Size Comes From

Bitrate is the amount of data the video consumes per second, usually measured in kbps or Mbps. A 10-minute video at 10 Mbps weighs in at around 750 MB; drop the bitrate to 2 Mbps and it shrinks to roughly 150 MB.

Rule of thumb: size ≈ bitrate × duration. The most direct way to shrink a file is to lower the bitrate.

Resolution: Don't Rush to Downscale

Cutting 1080p down to 720p does reduce file size significantly, but it also costs you sharpness directly. Modern encoders are often much better at squeezing the bitrate down at the original resolution than you'd expect — lower the bitrate first, and only drop the resolution if the results disappoint.

Encoding: H.264 vs. H.265

• H.264: the most compatible option — virtually every device and platform can play it.
• H.265: typically 30%–50% smaller than H.264 at the same quality, but some older devices don't support it.

If your video will play on the web, H.264 remains the safe choice; for archiving or distributing large files, H.265 is the better deal.

How to Do It on compressvid.io

1. Upload your video to the online video compressor and pick the "50% smaller" preset, or type an exact Target size in MB — the bitrate is calculated from that size and the video's length.
2. For precise control, switch to Advanced and choose the codec (H.264 or H.265) and quality (CRF) manually.
3. Before you start, the estimated credit cost is shown below the Compress button.

Need to hit a platform limit? See how to compress a video to an exact file size. For the complete walkthrough (devices, tools, quality checklist), read how to compress a video.

Once compression finishes, the output file stays available for download for about 24 hours; the source file is not kept.