The first time a client downloads TTWeb they will download The TTWeb OCX and supporting files, a typical TTWeb setup would be less then 3Mb download.

With each consecutive connection only the configuration files are sent, usually less then 200Kb, unless a different emulation is used. Then the new emulation is also downloaded, this only happens once per emulation used.

If you update TTWeb the updates will automatically be downloaded to the clients the next time they start TTWeb.