Yes & No. The first thing to know is that guidelines may vary by state. The second is that things like signed witnesses are greatly preferred and generally req

Yes & No. The first thing to know is that guidelines may vary by state. The second is that things like signed witnesses are greatly preferred and generally required to grant a will automatic legitimacy, but not strictly required for a will to hold up in court [1], and then only if the will is challenged anyway. An unwitnessed[2] will of this sort is usually termed a hollographic will. Most states recognize these, most other states will recognize them if they were created in a state that does so. Such a will has to clearly express the intent to act as such based on its language and it has to be clear that it came from the deceased. Traditionally that would mean handwritten but courts are slowly adapting to the digital age-- they key thing is the ability to attribute authorship to the deceased. Even putting all of that aside, just about any document from the deceased attesting to the deceased wishes can be used as an instrument for disposing of an estate, at least so long as it doesn't conflict with any other document that meets that state's probate requirements as a will. In short, if beneficiaries agree on the issue then all is generally fine no matter the document. If they don't, the courts have to settle things and they give preference first to witnessed documents but make an honest effort to adhere to the wishes of the deceased as expressed in other ways. (Even witnessed speech acts by the deceased are admissable) [1] source: a close relative practices family law and deals with this type of mess all of the time, even when they're the one that made the will & organized its signing and witnessing. [2] "Witness" has a legal definition which itself may vary by jurisdiction by it usually included a requirement to sign the document, not merely be present to attest to things at some later point. (Notarization is a good idea as well but generally not required)