The legitimate solution isn't found on a DLL download site. It is found in the philosophy of the GPL (General Public License).
Keep in mind that these methods might not provide the exact version of avformat-59.dll you're looking for, and you should ensure you're downloading from a trusted source. avformat59dll free
If a specific app (e.g., OBS Studio, Shotcut, HandBrake) is reporting the missing DLL, instead of hunting for the DLL. Most video tools bundle their own working version of FFmpeg. The legitimate solution isn't found on a DLL download site
and browse to the folder where FFmpeg was installed (usually C:\Program Files\FFmpeg For Audacity Match Architecture: HandBrake) is reporting the missing DLL
Developers incorporating FFmpeg into their projects might need specific versions of these libraries for compatibility or to access certain features.