If you’re interested in a particular charity organization, you can look them up on Charity Navigator. They pull information from the charity’s IRS filings as well as their website to rate various aspects. They give a breakdown of things like the fraction of funds spent on administrative costs, privacy policies, fundraising efficiency, etc.
They also provide the contact information and website for the charity. This way you know you’re donating to the actual charity and not a scammer impersonating them.