The base HTML/javascript coming from the itty.bitty server does not make it smaller. As a matter of fact, it appears that the javascript provided by itty.bitty

The base HTML/javascript coming from the itty.bitty server does not make it smaller. As a matter of fact, it appears that the javascript provided by itty.bitty simply decompresses the URL fragment and then converts it into a data-URI and passes that to an iframe. So it is smaller than a data URI - but only because it is compressed.