A tar bundle compressed with gzip - the standard Unix archive. Because gzip sees the whole bundle at once rather than each file separately, a folder of similar files compresses better than the ZIP equivalent. The catch is that reaching one file means decompressing everything before it.

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 TGZ file above and choose afterwards.