Yes, it is completely free... You pay for the more advanced features, but over the last ten years or so, I have met my last 6 lovers through the site ( though oftentimes it turns out that we already knew the same people... The matching algorithms are simply_that_ *good*!) and have never given them a single penny.
( though honestly, I really should, if only out of gratitude!)

Give it a try, it really is head and shoulders above the rest of the sites out there...!

YES, all the most desired features at okcupid are free. They sell you on tweaks that 1) ALLOW YOU TO SPY IN SECRET onto other profiles undetected, & 2) HIDE YOU FROM STALKERS...

A 3rd item they sell you EXPANDS YOUR MAILBOX.

You have to watch you data amount. Every time you send a HELLO to some one it counts as 1 message and you are allotted 300. So it can go fast. You must watch you items sent & items received closely to not run out. Its much easier than all that sounds. I never have more than about 50 items on count. IF YOU START AN ONGOING CONVERSATION, those count much slower.

So now you know. Just remember, BUYER BEWARE. This site can be glorious at times and the rest... ITS A FREAKIN LOONEY BIN.