In computing, I'm used to talk about "authenticating against a server". However, it came to my attention that many people use "with" instead of "against" on that sentence, and the Google test seems to prove them right.

Are both valid expressions? Do they mean exactly the same? Do you know any dictionary or style guide out there that states either that one of them is the only valid expression or that one of them is better than the other one?


Generally, a user authenticates to something with something. A user is proving he or she is entitled to access something based on something he or she has. For example,

The user must authenticate to the host with Active Directory credentials.

In more complicated scenarios 'against' might be useful. For example,

The user will be authenticating against the Active Directory's Kerberos server.

The definition of against as "compared or contrasted with" is being used rather than "in opposition to".

The user must authenticate to the host with Active Directory credentials because authentication is against the Kerberos server.

In a way, 'against' is thinking from the server's point of view. A user provides credentials and the server compares them to its user table.

I use Microsoft Manual of Style and couldn't find a recommended style. I use 'to' and 'with' when I'm writing for end-users and I use 'against' when writing for administrators.

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    If I may put it this way: You authenticate to a server, just like you have connected to this server beforehand. – Gras Double Oct 27 '15 at 19:13
  • And you are authenticating against the Stack Exchange user tables. – Val Aug 17 '16 at 15:45

It's 'authenticating with a server' - why would you want to be 'authenticating against a server'?

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    For the same reasons that you check something against a fact sheet. Authentication is confirming your credentials with a server against a database (or whatever other means of confirmation is used). If the server is used synecdochically for the database that is used as ‘fact sheet’, it makes perfect sense to say that you’re authenticating against the server. – Janus Bahs Jacquet Feb 5 '15 at 17:10
  • "with" is ambiguous w.r.t. means or target: you don't authenticate with a server in the same sense you authenticate with your PIN. (To avoid confusion, I'd say "authenticate against (target) by (means)" and not use with for either. – Ulrich Schwarz Feb 5 '15 at 17:25

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