Why do so many think that MacKeeper is free?
Yes, it is free to download and try.
https://mackeeper.com/buy-now-benso...mzb&guid=df987123-3388-11e8-9e38-0e846d25c658
Only $14.95 for a month, or $4.95/month, if you sign up for 2 years...
Oh, then you have to put up with paying for software - which does very little that you can't get for free somewhere else.
Bad history with MacKeeper, and Zeobit software (Sorry, now "Kromtech Alliance Corporation") - and the company has done very little to dispel that impression.
Short wiki article
I think that you will not find too many folks who are often here that will have much good to say about MacKeeper (other than those who work for MacKeeper, if that makes you more comfortable)