How to Compress or Reduce Video File Size with FFmpeg? (The Perfect Balance)

Have you ever faced this problem: you've recorded a high-quality video, but the file size is enormous, making it impossible to send via email or messaging apps? Or maybe you want to embed a video on your website but worry that the huge file will slow down page load times. The truth is, you can significantly reduce video size without a major sacrifice in quality. FFmpeg offers a nearly perfect solution that allows you to precisely control the compression level, striking the best balance between quality and size.

🚀 Quick Access: The FFmpeg Command

Want to significantly compress a video named input.mp4 while maintaining great visual quality? Copy and run the following command:

ffmpeg -i input.mp4 -vcodec libx264 -crf 23 output.mp4

This command uses the H.264 encoder to intelligently compress the video using a parameter called CRF (Constant Rate Factor).

🧠 The Breakdown: Understanding Each Parameter

Let's dive deep into each component of this command.

Parameter	Explanation
ffmpeg	Calls the FFmpeg program.
-i input.mp4	Specifies your input file—the original, oversized video.
-vcodec libx264	-vcodec is used to specify the video encoder. libx264 is the most widely used and compatible H.264 video encoder available today.
-crf 23	This is the core of the compression! CRF (Constant Rate Factor) is the parameter that controls the video quality. A lower value means higher quality and a larger file; a higher value means lower quality and a smaller file.
output.mp4	The filename for the new, compressed output video.

A Practical Guide to CRF Values:

• 18 is considered to be visually lossless or nearly so, but the compression effect is minimal.
• 23 is the default value for libx264 and provides an excellent balance between quality and file size.
• 28 is a more aggressive value that will result in a much smaller file, but the quality loss might be noticeable.
• You can start with 23 and adjust the value up or down based on your results.

FAQ & Variations

1. The compression process is too slow. Is there a way to speed it up?

Absolutely! FFmpeg offers a -preset parameter that dictates how much effort the encoder puts into compression. Faster presets result in lower compression efficiency (i.e., a slightly larger file for the same CRF), while slower presets are more efficient.

# Use the "veryfast" preset to significantly speed up the process
ffmpeg -i input.mp4 -vcodec libx264 -preset veryfast -crf 23 output.mp4

Available preset values include: ultrafast, superfast, veryfast, faster, fast, medium (the default), slow, slower, veryslow. For most day-to-day tasks, veryfast is an excellent choice for speed and efficiency.

2. How can I use the newer, more efficient H.265 (HEVC) encoder for compression?

If your playback devices support it, using libx265 (the H.265/HEVC encoder) can achieve similar visual quality to H.264 at an even smaller file size. The command is very similar; you just need to change the encoder and the corresponding CRF value.

# Compress using the H.265 encoder
ffmpeg -i input.mp4 -vcodec libx265 -crf 28 output.mp4

Note: The CRF scale for libx265 is different from libx264. The default CRF for libx265 is 28, which is intended to provide a similar perceptual quality to libx264 at its default of 23.