Get the tool from the Microsoft Download Center .

You cannot use a 2019 offline installer to install Office 2021. The version must match your product key or Microsoft 365 subscription exactly.

If you’re managing a business environment, you’ll likely use the .

Or for fully silent (no UI):

If you need only the core apps, Microsoft offers (one‑time purchase) as an offline installer via the same ODT method described above. Specify <Product ID="HomeStudent2019Retail"> in the XML.

If you have a standard Microsoft 365 retail subscription, you can easily download a complete disk image (often an .IMG or .ISO file) directly from your account dashboard.