How an FFmpeg command is structured
Most FFmpeg commands follow the same shape: ffmpeg, then input options, then -i input, then output options, then the output file. For example, -c copy after the input tells FFmpeg to stream-copy (repackage) without re-encoding, while -c:v libx264 re-encodes the video. The generator above fills these pieces in for you based on the task you pick.
Remux vs re-encode
If the source already uses MP4-compatible codecs, a remux (-c copy) is instant and lossless. Re-encoding (libx264, CRF) is needed to change codec, compress, or resize, and it takes longer because FFmpeg decodes and encodes every frame. Choose the operation that matches your goal to avoid unnecessary quality loss.
Frequently asked questions
Does this run FFmpeg for me?
No. This tool only builds the command text. Copy it into a terminal where FFmpeg is installed to run it. If you want in-browser conversion with no install, use the MP4, MP3, GIF, or compressor tools instead.
What is CRF in the compress command?
CRF (Constant Rate Factor) controls quality versus size for H.264. Lower values mean higher quality and larger files; 18 is visually lossless, 23 is a common default, and 28 produces noticeably smaller files.
Why does the trim command use -ss before -i?
Placing -ss before -i makes FFmpeg seek quickly to the start time before decoding, which is faster. Combined with -c copy it trims without re-encoding, though cuts land on the nearest keyframe.
Is the FFmpeg command generator free?
Yes. It is completely free, requires no sign-up, and runs entirely in your browser.