How to Compress Large Videos Without Losing Much Quality Using FFmpeg

Recording tutorials, gameplay, or OBS sessions often results in videos that are several gigabytes in size. Uploading or storing these files quickly becomes expensive, especially when working with limited disk space or slower internet connections. Fortunately, FFmpeg makes it possible to reduce video size significantly while maintaining excellent visual quality.

In this guide, you'll learn how to compress MP4, MKV, and other video formats using FFmpeg, understand the most important encoding options, and avoid common mistakes that lead to poor quality or corrupted files.

What is FFmpeg?

FFmpeg is a free and open source multimedia framework that allows you to record, convert, compress, stream, and edit audio and video directly from the command line. It is available for Windows, Linux, and macOS and is trusted by developers, video editors, and streaming platforms.

Using FFmpeg to compress large video files

Why Compress Videos?

Compressing videos has several advantages:

Save storage space
Upload videos faster
Reduce bandwidth usage
Share files more easily
Archive recordings efficiently

Installing FFmpeg

Ubuntu:

sudo apt update
sudo apt install ffmpeg

Verify the installation:

ffmpeg -version

Basic Compression Command

The following command provides a great balance between quality and file size:

ffmpeg -i input.mp4 \
-c:v libx264 \
-crf 23 \
-preset medium \
-c:a aac \
-b:a 128k \
output.mp4

Understanding Each Option

Option	Description
libx264	Uses the H.264 video encoder.
CRF	Controls video quality. Lower values produce higher quality and larger files.
Preset	Determines encoding speed versus compression efficiency.
AAC	Compresses audio while maintaining good quality.

Choosing the Right CRF Value

CRF	Quality	File Size
18	Excellent	Large
23	Recommended	Balanced
28	Acceptable	Small
35+	Poor	Very Small

Compress Every Video Inside a Folder

If you have many recordings, use a simple Bash loop:

mkdir compressed

for file in *.mkv; do
    ffmpeg -i "$file" \
    -c:v libx264 \
    -crf 23 \
    -preset medium \
    -c:a aac \
    -b:a 128k \
    "compressed/${file%.mkv}.mp4"
done

This script converts every MKV file in the current directory into a compressed MP4 version inside the compressed folder.

Speed vs Compression

Preset	Encoding Speed	Compression
ultrafast	Very Fast	Poor
fast	Fast	Good
medium	Balanced	Very Good
slow	Slow	Excellent
veryslow	Very Slow	Best

Common Mistakes

Using a CRF value that is too high, resulting in blurry videos.
Choosing the ultrafast preset for permanent archives.
Overwriting the original recording before checking the compressed version.
Compressing an already compressed video multiple times.
Ignoring audio bitrate, which can noticeably reduce sound quality.

Recommended Settings

Purpose	CRF	Preset
YouTube Upload	23	medium
OBS Recordings	22	slow
Long-term Archive	18	slow
Quick Sharing	28	fast

Final Thoughts

FFmpeg is one of the most powerful tools available for video compression. By combining the H.264 encoder with a sensible CRF value and an appropriate preset, you can reduce file sizes dramatically while preserving excellent visual quality. Whether you're compressing tutorial videos, OBS recordings, or personal archives, these settings provide a reliable starting point for most workflows.

Written by A.M. Rinas