'log in to' or 'log into'?

[Andrew Warren]

Claire Conant wrote:

> When documenting software, I always follow Microsoft Manual of
> Style. Here's what it says:
> ....
> Use log on or log on to (not log onto) to refer to creating a
> user session on a computer or a network. .... Use sign in and
> sign out to refer to creating and ending a user session on the
> Internet.

Claire:

With all due respect to the geniuses at Microsoft, I disagree.  These days, there's generally no user-discernable difference between creating a session on a computer, a network, or the internet/Internet.

The "verb form is two words, noun form is one" rule is fine, as is the clarification that the verb is "log on" rather than "log" (hence "log on to" rather than "log onto")... But if I were deciding among "log in", "log on", "sign in", and "sign on", I'd probably just do a Google search and go with the most prevalent usage, since that's what's likely to be familiar to my readers.

Google says:

  "sign on" password username:    295K hits
  "log on" password username:     415K hits
  "sign in" password username:  4,690K hits
  "log in" password username:  21,000K hits

Searching for the "ending a session" idiom, we find a similar pattern:

  "sign off" password username: 154K hits
  "log off" password username:  380K hits
  "sign out" password username: 311K hits
  "log out" password username:  940K hits

So I'd use "log in" and "log out", and I'd use those phrases consistently, without trying to manufacture a difference between logging in to a computer and logging in to the internet.

-Andrew