UL

In computing and internet slang, UL means to upload — the reverse of DL (download). It's been part of tech and file-sharing communities since the dial-up era, appearing on forums, FTP sites, and peer-to-peer networks where every byte of bandwidth mattered. Separately, UL also refers to Underwriters Laboratories, the US product-safety testing organization whose seal appears on electrical devices. Context tells you which one you're dealing with.