One of the oldest principles of estate law is that to be valid, a will must be signed by the testator. This is true whether the will was a formal will that had a signature, was witnessed and notarized. The signature had to be made by the testator.
Even if the will was an informal one, known as a holographic will, that the testator wrote him or herself, it still needed to be signed. Somewhere on the document, the person whose will it was supposed to be, had to sign the document.
This has been the case for centuries. However, but an appellate court in Michigan recently ruled otherwise, as the Wills, Trusts & Estates Prof Blog reported in "Unsigned Will? No problem!"
The court's decision rests on the interplay of two Michigan statutes, so it is not expected to spread to other states with different statutes.
The court decided that if the person presenting the will to the court can prove by clear and convincing evidence that it is the will of the deceased, then the court can accept the will for probate. Exactly how that can be proven without a signature is unclear.
Of course, this is not the law in any other state.
If you want to create a will outside of Michigan, then you will need to follow the appropriate legal process in your state. The best way to do that is to see an estate planning attorney who can draft a valid will for you.
Reference: Wills, Trusts & Estates Prof Blog (August 7, 2017) "Unsigned Will? No problem!"