Troubleshooting Skype for Business (Lync)

This article is a collection of useful resources to help you in troubleshooting Skype for Business (Lync).

SfB/Lync Log File Locations

Windows Client Logs

SfB 2016: %userprofile%\AppData\Local\Microsoft\Office\16.0\Lync\Tracing
Lync 2013/SfB 2015: %userprofile%\AppData\Local\Microsoft\Office\15.0\Lync\Tracing
Lync 2010: %userprofile%\tracing

Log File: Lync-UccApi-#.UccApilog

Web App Logs

Add ?sl=1&log=full to the end of your meet url to enable detailed logging

Log location: %userprofile%\AppData\Local\Microsoft\LWAPlugin\Tracing and look for a file name
Log file name: LWAJSPersistent#.log

Lync Server Logs

Lync 2010/2013 tracing – C:\WindowsTracing


Lync Windows Client Cache

Its often a useful troubleshooting step to delete the Lync client side cache, in particular when dealing with address book issues. You can find the client cache folders as follows. Its safe to delete the entire sip_<user>@<domain> folder. Note that to do this you will need to exit the Lync client.

SfB 2016


Lync 2013/SfB 2015


Lync 2010



Address Book Cache

Deleting Address Book Server Side Cache

Its often a useful troubleshooting step to delete the address book server side cache when dealing with address book issues. This step would be used if deleting the users client cache hasn’t helped. After deleting the server side cache, it would be advisable to delete the users client cache, then re-test.

  1. Navigate to \\<Lync File Share>\<#>-WebServices-<#>\ABFiles\00000000-0000-0000-0000-000000000000\00000000-0000-0000-0000-000000000000
  2. Delete all files within this directory
  3. Open Lync/SfB PowerShell
  4. Optionally, run Update-CsUserDatabase – This synchronizes data between AD and Lync backend DB (rtcab). This step should not be necessary under normal circumstances and may take some time to complete. Look for Event Log 21010 – “Synchronization pass completed successfully. Address Book web service backend data partition” to confrm
  5. Run Update-CsAddressBook – This writes changes in backend DB to the address book files
  6. Check the file share location to confirm files have been re-created


Address Book URL’s

Make sure that you can browse to the following URL’s. You should receive an authentication challenge.

https://<internal or external web services URL>/abs/handler
https://<internal or external web services URL>/abs/handler/GroupExpansion/Service.svc

Lyncdiscover URL

Mobility MCX Service URL

Web Apps

Service URL –

If the result is successful, you should see the XML content in your browser.

Edge Replication Service

https://<Edge Internal>:4443/ReplicationWebService

Lync Troubleshooting Tools

This is a collection of tools that I regularly use when troubleshooting a Lync client or server issue.


Thanks to the LinkedIn community for expanding on this list. When time permits I will elaborate further on all the troubleshooting tools mentioned.


  1. slight correction though trivial
    there should be a / in the path after the second % sign.

    Lync 2013: %userprofile%AppDataLocalMicrosoftOffice15.0LyncTracing
    Lync 2010: %userprofile%tracing


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