Copy all three FFmpeg DLLs ( avcodec , avformat , avutil ) together to avoid subsequent missing errors.
If you are seeing an error that avformat-59.dll is missing, the safest solution is to reinstall the software that uses it or download the library from its official source. Can't find avformat.dll - Windows 10 - Audacity 3.1.3
: If you are a developer or using a tool that requires a standalone FFmpeg installation, download the latest builds from the Official FFmpeg Site .
Check the official website of the app causing the error for any updates or patches. Developers often release fixes for missing library errors.