Once every year, you're guaranteed free access to your credit report via annualcreditreport.com, from each of the three credit reporting bureaus (TransUnion, Equifax and Experian). These reports, however, will not include your credit score, unless you choose to pay for it. Credit Karma and Credit Sesame both offer the opportunity to see your credit score for free.
The free credit score model, used by the two companies, grants you access to your credit score, in exchange for viewing loans, debt consolidation services and credit card offers, from their advertising partners. These offers are very likely ones that you qualify for, based on the preferences and information you share when you sign up.
While the credit scores available from the two sites, come from one (or two) of the credit bureaus, there is no guarantee that lenders will use the exact same score(s) to evaluate your creditworthiness - lenders may use a FICO or VantageScore, from another bureau, which could be different. The figures from Credit Karma and Credit Sesame are nonetheless a great way to educate yourself on your creditworthiness, monitor and improve your credit for free.
In addition to your credit score, Credit Sesame and Credit Karma, offer their own analysis of your credit, based on the information found on your credit report(s), from the same bureau(s) from which your score(s) is drawn. In both instances, you will again be served ads, with this analysis. Both companies also offer a "recommendations section. While these may be valuable suggestions for improving your credit, keep in mind that the recommendations are geared towards selling you products from their advertising partners.
The two sites are not driven solely by ads. Each also offers paid services. To see your credit scores from more than one bureau for example, Credit Sesame requires paid membership. Based on the tier selected, additional services like public records monitoring, identity theft restoration and identity theft insurance, may also be included in the package.
Credit Karma offers scores from two bureaus for free, but charges for direct access to your credit report. Considering that the company provides free analysis of the information found in the report, and given the yearly option to access your report for free, purchasing a credit report from Credit Karma, may not be necessary.
Neither site sells your information to third parties, but you may be added to email listservs, when you sign up. Credit Sesame automatically opts you in; with Credit Karma, it's incumbent on the user to sign up for promotional emails.
As long as you're comfortable viewing advertisements in exchange for access to your credit score, these websites both provide valuable information for free. Moreover, the information is updated monthly. Unlike the free credit report you access once a year from a credit-reporting bureau, these services give you constant up-to-date access to your score. That monitoring ability - plus the analysis of your credit report - can alert you when a change to your report necessitates an inquiry with the relevant credit bureau.