Most of these keys are either expired, blocked by Microsoft, or meant for large organizations.
However, there are several to use Microsoft Office for free or at a significantly reduced cost. This guide outlines those legitimate methods. microsoft office free product keys
Avoid "free product keys" found on the internet. Instead, use the free web version, check your student or work eligibility, or use a legitimate free alternative like LibreOffice. Most of these keys are either expired, blocked