Microsoft 365 uses 40 prefixes for Microsoft 365 Common and Office Online.
Short answer
Common: Microsoft 365 apps, sign-in (Entra ID) and services shared by the others.
Prefixes
What changed
No prefixes added or removed since we started tracking this list. Changes appear here the day after the provider publishes them.
Allowlist formats
nginx (first 5 prefixes)
allow 13.107.140.6/32; allow 13.107.18.15/32; allow 13.107.6.171/32; allow 13.107.6.192/32; allow 13.107.9.192/32; deny all;
iptables (first 5 prefixes)
iptables -A INPUT -s 13.107.140.6/32 -j ACCEPT iptables -A INPUT -s 13.107.18.15/32 -j ACCEPT iptables -A INPUT -s 13.107.6.171/32 -j ACCEPT iptables -A INPUT -s 13.107.6.192/32 -j ACCEPT iptables -A INPUT -s 13.107.9.192/32 -j ACCEPT
Generate the full list from the CSV, and refresh it on a schedule: providers add and retire prefixes often.
Sources
- Microsoft 365: published IP ranges · checked 5 Nov 2026
- Microsoft 365 documentation