How to Convert Video to MP4, WebM, MOV with FFmpeg (2026 Guide)

Need to convert a video from MOV to MP4? Or compress a WebM file for web delivery? FFmpeg is the most powerful command-line tool for video conversion—but it comes with a steep learning curve. This guide walks you through every common video conversion scenario with exact commands you can copy and paste.

And if you’d rather skip the terminal entirely, we’ll show you a free one-click alternative at the end.

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Prerequisites: Install FFmpeg

Before you start, you need FFmpeg installed on your system.

macOS (Homebrew):

brew install ffmpeg

Ubuntu/Debian:

sudo apt update && sudo apt install ffmpeg

Windows:

1. Download from ffmpeg.org
2. Extract the archive
3. Add the bin folder to your system PATH

Verify the installation:

ffmpeg -version

If this already feels like a lot—don’t worry, it gets more complicated from here.

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Basic Video Conversion

MOV to MP4

The most common conversion. Apple devices record in MOV, but MP4 is universally supported:

ffmpeg -i input.mov -c:v libx264 -c:a aac -movflags +faststart output.mp4

What each flag does:

• -i input.mov — input file
• -c:v libx264 — encode video with H.264 codec
• -c:a aac — encode audio with AAC codec
• -movflags +faststart — optimize for web streaming (moves metadata to the beginning)

MP4 to WebM

WebM is preferred for web browsers and offers better compression:

ffmpeg -i input.mp4 -c:v libvpx-vp9 -crf 30 -b:v 0 -c:a libopus output.webm

Parameters explained:

• -c:v libvpx-vp9 — VP9 video codec (used by YouTube)
• -crf 30 — quality level (lower = better quality, 15–35 is typical)
• -b:v 0 — let CRF control the bitrate
• -c:a libopus — Opus audio codec (best for WebM)

MP4 to MOV

ffmpeg -i input.mp4 -c:v prores_ks -profile:v 3 -c:a pcm_s16le output.mov

This creates a ProRes MOV file suitable for professional editing in Final Cut Pro or DaVinci Resolve.

AVI to MP4

ffmpeg -i input.avi -c:v libx264 -crf 23 -c:a aac output.mp4

MKV to MP4

MKV to MP4 often works without re-encoding (just remuxing), which is much faster:

ffmpeg -i input.mkv -c copy output.mp4

The -c copy flag copies streams without re-encoding. This only works if the codecs inside MKV are MP4-compatible (usually H.264 + AAC).

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Advanced Options

Control Video Quality with CRF

CRF (Constant Rate Factor) controls the quality-to-size tradeoff:

ffmpeg -i input.mov -c:v libx264 -crf 18 -c:a aac output.mp4

CRF Value	Quality	Use Case
0	Lossless	Archiving
18	Visually lossless	High quality
23	Default	Good balance
28	Lower quality	Small file size
51	Worst	Not recommended

Set Specific Bitrate

ffmpeg -i input.mov -c:v libx264 -b:v 5M -c:a aac -b:a 192k output.mp4

• -b:v 5M — 5 Mbps video bitrate
• -b:a 192k — 192 kbps audio bitrate

Change Resolution

Scale to 1080p:

ffmpeg -i input.mov -vf "scale=1920:1080" -c:v libx264 -c:a aac output.mp4

Scale to 720p while keeping aspect ratio:

ffmpeg -i input.mov -vf "scale=-1:720" -c:v libx264 -c:a aac output.mp4

Change Frame Rate

Convert to 30fps:

ffmpeg -i input.mov -r 30 -c:v libx264 -c:a aac output.mp4

Two-Pass Encoding (Best Quality)

For the best possible quality at a target bitrate:

ffmpeg -i input.mov -c:v libx264 -b:v 5M -pass 1 -an -f null /dev/null
ffmpeg -i input.mov -c:v libx264 -b:v 5M -pass 2 -c:a aac output.mp4

On Windows, replace /dev/null with NUL.

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Batch Conversion

Convert All MOV Files to MP4

Linux/macOS:

for f in *.mov; do
  ffmpeg -i "$f" -c:v libx264 -crf 23 -c:a aac "${f%.mov}.mp4"
done

Windows (PowerShell):

Get-ChildItem *.mov | ForEach-Object {
  ffmpeg -i $_.Name -c:v libx264 -crf 23 -c:a aac ($_.BaseName + ".mp4")
}

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Common Errors and Fixes

“Codec not found” or “Unknown encoder” You may need to install FFmpeg with additional codec support:

# macOS
brew reinstall ffmpeg

# Ubuntu
sudo apt install ffmpeg libavcodec-extra

“Invalid data found when processing input” The input file may be corrupted. Try:

ffmpeg -err_detect ignore_err -i input.mov -c copy output.mp4

Output file is huge You forgot to set a CRF or bitrate. Without quality settings, FFmpeg may use very high bitrates:

# Add -crf 23 for reasonable quality/size
ffmpeg -i input.mov -c:v libx264 -crf 23 -c:a aac output.mp4

“height/width not divisible by 2” Some codecs require even dimensions:

ffmpeg -i input.mov -vf "scale=trunc(iw/2)*2:trunc(ih/2)*2" -c:v libx264 output.mp4

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Skip the Terminal: Use WaveSpeed Desktop Instead

Let’s be honest—remembering codec names, CRF values, two-pass encoding flags, and batch conversion scripts is not everyone’s idea of a good time.

WaveSpeed Desktop includes a built-in Video Converter that handles all of the above with a single click:

• Drag and drop your video file
• Pick the output format (MP4, WebM, MOV, AVI)
• Click convert — done

No installation of FFmpeg. No terminal. No memorizing flags.

Download WaveSpeed Desktop for free: https://github.com/WaveSpeedAI/wavespeed-desktop/releases

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FAQ

What’s the best format for sharing videos online? MP4 with H.264 video and AAC audio. It’s supported by virtually every platform, browser, and device.

Does converting video reduce quality? Re-encoding always introduces some quality loss. Use -c copy when possible to avoid re-encoding. If you must re-encode, use a low CRF value (18–20) for near-lossless quality.

How long does FFmpeg take to convert a video? It depends on the file size, codec, and your hardware. A 1GB MOV to MP4 conversion typically takes 2–10 minutes on modern hardware. Using -c copy (remuxing) takes seconds.

Can FFmpeg handle 4K and 8K video? Yes, but encoding high-resolution video is CPU-intensive and slow. Consider using hardware acceleration (-c:v h264_nvenc for NVIDIA GPUs) for faster processing.