N.W.
As some of the other posters have said, beware of the ones advertized, but the government site https://www.annualcreditreport.com/cra/index.jsp
is good you can use it once a year and it is linked so that you are directed to each of the 3 services one after the other as soon as you finish getting the report from one it sends you on to the next one. As long as you don't click yes to any of the money charging offers while on each site, there is no charge.