FortiGate Next Generation Firewall utilizes purpose-built security processors and threat intelligence security services from FortiGuard labs to deliver top-rated protection and high performance, including encrypted traffic.
This article describes how to block only Google and Facebook chats, while allowing the rest of navigation and features such as email, video, browsing etc.

1) Enable SSL Inspection profile as Deep Inspection.

2) Application Control, blocked signatures:

- All Facebook.Messenger signatures depending on what is desired to block: Image, Video, Voice, VoIP.
- Google Hangouts.
- Google Talks.
- QUIC for workstations using Google Chrome.

3) CASI (Cloud Access Security Inspection, introduced in FortiOS 5.4) profile.

4) Block Google Hangouts & chat.

5) Block Facebook chat.