Qix

Maybe, but what do I do if the header is missing? Use the latest version?

If I use the latest version it is likely developers will simple leave the header out since it "Just Works" without it.

Then when I make a breaking change to the latest API those applications will get screwed. Yes its mostly their fault -- but its my problem.

How about putting the version number in the hostname?

https://api-v1.xxxy.com/clients/list

I believe its a little neater than /v1/clients/list, albeit a little less standard.

I liked your idea #5 (Website visualizer) and have been looking for an excuse to play with the Raphael javascript library.

Just hacked together a little initial demo (still needs a lot of work), but think it will look decent when I'm done with it.

Posted on github.com at http://github.com/qix/Sitemap