Why do I have .SEC files? (YI 4K+ Action Camera) .SEC files are much lower in bit-rate which allows you to quickly preview videos on the app. Related articles What is a .thm file? Why do I have .SEC files? (YI 4K Action Camera) What is the bitrate for each resolution? Why are the photos and videos distorted on the margins?(YI 4K+ Action Camera) What are the requirements for my microSD card?(YI 4K Action Camera)