There are various synonyms that can be used instead of "witness to" depending on the context you want to convey. For instance, "observe" refers to seeing an event or action without necessarily being involved in it. On the other hand, "experience" denotes undergoing or encountering something directly. In addition, "see" might be used to indicate having visual comprehension of an occurrence or development. Similarly, testify implies providing evidence or a statement regarding an event that one has seen or been involved with, while "attest" communicates verifying or confirming the authenticity of something. Moreover, "certify" might be used to convey formally attesting to the truth or accuracy of something.