What is the latest Skype for Business User-Agent string?

When using a client other than Skype for Business (formerly known as Lync) to connect with your Office 365 account, you’ll need to provide the Microsoft Lync servers with a user-agent string they recognize as an “acceptable” client. The reasoning behind this is surely to give you the best possible experience and not at all to lock out other messaging clients.

Personally, I use Pidgin with the third party plugin “pidgin-sipe” to connect with the Office 365 service. However, this will only work as long as an “acceptable” user-agent string is provided.

As of February 2021, Skype for Business identifies itself with the following user-agent string:

User-Agent: UCCAPI/16.0.13628.20000 OC/16.0.13628.20274

If you try to connect with an invalid user-agent string you’ll get the following message, which includes a link to download Skype.

CSeq: 6 REGISTER
Warning: 311 lcs.microsoft.com "http://go.microsoft.com/fwlink/?LinkID=213295"
Server: RTC/6.0

I’ll keep this information up to date as long as I have a valid Office 365 subscription.

Older entries:

*= Current User-Agent from Skype for Business 2015
This page was last updated on Monday February 01, 2021.