guides
The decisions behind the buttons.
Every tool here shows you the command it runs. These guides explain why the command looks the way it does, so you can choose settings on purpose rather than by trial and error.
What actually shrinks a video file, what each control costs you in quality, and how to pick settings for a target size without guessing.
Containers are not codecsWhy converting between video formats is sometimes instant and sometimes an hour, what a container actually holds, and how to tell which kind of conversion you need.
When a GIF is the wrong choiceWhy GIFs are so large and so muddy, how palette generation fixes the colour, and when a short MP4 or WebM is the better answer.
Audio formats, and what the bitrate number meansLossy versus lossless, what bitrate numbers mean, why re-encoding degrades sound, and how to pick a format for listening, editing, archiving and sharing.
Captions people can actually readHow to make captions that people can actually read: how long a line should be, how long it should stay up, where to put it, and when to burn it in rather than attach a subtitle file.
What a photo knows about youWhat metadata a phone writes into every photo and video, which of it survives sharing, how to look at it, how to strip it, and what stripping cannot do.
Getting the frame right for where it is goingThe frame sizes each platform actually wants, how to go between landscape and vertical without ruining the shot, and why upscaling is not what it sounds like.
Taking the command with youEvery tool on this site shows its FFmpeg command. Here is how to read it, run it yourself, apply it to a folder of files, and get past the errors you will meet first.
How these are written
Each guide is written by the person who built the tools, from what the FFmpeg build on this site actually does, and is checked against it: where a guide says a tool defaults to a value or uses a particular filter, that is read from the tool itself. Where general advice and this build disagree, as with VP9 encoding, the guide says so. The date on each guide is the last time the text was revised, not the last time the page was generated.
If a guide is wrong, or you would like one on something the tools do that is not covered, the contact page says how to reach the author.