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 does the battery percentage indication display inaccurately? What are the requirements for my microSD card?(YI 4K Action Camera)