There's nothing like the law for providing tricky, complicated answers to simple questions. With a promise to provide as straightforward an answer as possible, let's look into one of those seemingly simple questions. In the United States, are last wills and testaments a matter of public record, accessible to anybody? Wills, of course, are documents prepared to control the disposition of property after an individual's death. As such they're a matter of keen interest to heirs, potential heirs, and anyone else with an interest in how any individual has chosen to divvy up his property. Wills also provide a complete picture as of a certain point in time, a snapshot, of the entire holdings of the estate of the decedent, so they're also going to be of interest to the taxman, creditors, and any other claimants to the assets of the estate. For public figures wills can be a gold mine of more qualitative information for researchers and biographers. Before a will is filed with the local probate court it is in no way a public document.
At the death of the testator, the will is filed with the probate court, and at the point the will becomes a matter of public record -- theoretically. Unfortunately, "public record" does not necessarily and automatically mean "free access". Probate law is state law. So in the United States, probate law takes 50 different rules, with 50 different basic sets of rules and regulations. Probate law is one of those areas that has stubbornly resisted attempts at standardization. Therefore, states are going to differ in how they'll allow access to will.
To make it more complicated, some individual Probate Courts on a district or municipal level will have their own access rules. These individual jurisdictions can place significant restrictions on access to these documents, in the interests of maintaining a level of privacy for the decedent and the family. There may be no restrictions whatsoever. If there are, the good news is that wills are in the class of "public records", and that means the courts are compelled to provide some kind of procedural avenue to gain access to the filed documents. You may need to file a request, you may have to wait a few weeks, and you may even need to justify your reasons for reviewing the document.