Or save a bookmark in your browser and edit its destination to be this Javascript bookmarklet to let you load the archive.is version of any URL you're currently on without even needing to remember the ___domain or type anything:

  javascript:void(___location.href='https://archive.is/?run=1&url='+encodeURIComponent(___location.href))

Or version for IA's Wayback Machine instead:

  javascript:void(window.open('https://web.archive.org/web/*/'+___location.href))

(The archive.is one takes you to it in the same tab, while the wayback machine one opens a new one - because personally I use the former when I can't load a page, so don't need that tab kept open, and use the W.M. for comparing current to old versions of the page. But it should be fairly self-explanatory how to swap one URL with the other if you prefer it differently.)

Or this more complicated version of the Wayback Machine one, which if you click while on an empty tab will instead give you an alert with a text field in which to type or paste whatever URL you want to look up:

  javascript:(function()%7Bif(___location.href.indexOf('http')!=0)%7Binput=prompt('URL:','https://');if(input!=null)%7Blocation.href='http://web.archive.org/web/*/'+input%7D%7Delse%7Blocation.href='http://web.archive.org/web/*/'+___location.href;%7D%7D)();