WOFF is a font wrapped for the web - the same TrueType or OpenType tables, each compressed, in a container browsers fetch happily. That is the whole format, which is why converting between WOFF and TTF or OTF is lossless repackaging rather than a redraw.
Every conversion below runs in this page, on your own machine. Nothing is uploaded, there is no queue, and there is no account to make. Pick a target format, or just drop a WOFF file above and choose afterwards.