Freemake Video Converter operates on a freemium model:

There are no legitimate "free activation keys" circulating online. Websites claiming to offer keys for version 4.1.13 are typically:

Freemake Video Converter is a popular video conversion tool that supports over 500 formats. Version 4.1.13 was released several years ago, and while still functional, users seeking "activation keys" often misunderstand the software's licensing model.

Files labeled "freemake video converter 4.1.13 activation key full" have been analyzed by cybersecurity researchers. Many contain:

This paper explores the legitimate, safe, and legal use of Freemake Video Converter’s free version, focusing on its core capabilities, limitations, and how users can accomplish common video conversion tasks without resorting to unauthorized activation.

A lifetime license costs around $30-$40 and supports ongoing development.