Client Logs & Diagnostics
When Teams breaks, the logs tell the story. Learn to collect client logs, clear the cache, use self-help diagnostics, and troubleshoot installation, updates, and client health.
When Teams breaks
Client logs are like a flight recorder on an aeroplane.
When something goes wrong — a crash, a failed sign-in, a frozen meeting — the logs capture exactly what happened. You collect them, read the story, and fix the problem.
Clearing the cache is like rebooting your brain — it clears out stale data that might be causing issues. Self-help diagnostics are like a doctor’s automated health check — you type your symptoms and it runs tests automatically.
Collecting client logs
Desktop client logs (Windows)
Method 1: Keyboard shortcut
- Press Ctrl + Alt + Shift + 1 in the Teams client
- Logs are saved to the Downloads folder as a .zip file
Method 2: Manual collection
- Navigate to:
%appdata%\Microsoft\Teams\(classic) or%localappdata%\Packages\MSTeams_*\LocalCache\(new Teams) - Key log files:
logs.txt— main application logmedia-stack\*.blog— media quality logs (audio/video)skylib\*.blog— signalling logs
What logs contain
| Log Type | Information | Use Case |
|---|---|---|
| Application logs | App errors, feature loading, API calls | Crashes, feature failures, performance issues |
| Media logs | Audio/video codec, packet loss, jitter, device info | Call quality troubleshooting |
| Auth logs | Sign-in attempts, token refresh, SSO events | Sign-in failures, authentication issues |
| Network logs | Connection attempts, DNS resolution, proxy traversal | Network connectivity issues |
Scenario: Jaylen collects logs for VP Rivera
VP Rivera at RemoteFirst reports that Teams “crashes every time I try to join a meeting.” Jaylen’s approach:
- Ask VP Rivera to press Ctrl + Alt + Shift + 1 during the next crash attempt
- Collect the .zip file from Downloads
- Open logs.txt — look for ERROR or FATAL entries near the crash timestamp
- Check media-stack logs — any codec initialization failures?
- Check auth logs — is the token expired or failing to refresh?
Finding: Auth log shows repeated token refresh failures → SSO token expired → VP Rivera’s device hasn’t synced with Entra ID in 30+ days. Fix: Re-authenticate the device + clear the cache.
Clearing the Teams client cache
Cache issues are one of the most common causes of Teams client problems. Clearing the cache resolves:
- Stale user profiles
- Corrupted meeting data
- Login loops
- UI glitches
- Presence sync issues
How to clear the cache
New Teams (Windows):
- Close Teams completely (check system tray)
- Press Win + R → type
%localappdata%\Packages\MSTeams_8wekyb3d8bbwe\LocalCache\Microsoft\MSTeams - Delete all files and folders in this directory
- Relaunch Teams
Classic Teams (if still in use):
- Close Teams completely
- Press Win + R → type
%appdata%\Microsoft\Teams - Delete contents of: Cache, blob_storage, databases, GPUCache, IndexedDB, Local Storage, tmp
- Relaunch Teams
Exam tip: Clearing the cache does NOT delete messages, files, or settings — those are stored server-side. It only removes locally cached data. Teams re-downloads everything on next launch.
Self-help diagnostics
Microsoft 365 admin center → Help & Support → type the issue → Run tests
Self-help diagnostics are automated troubleshooting tools that check for common issues:
| Diagnostic | What It Checks |
|---|---|
| Teams meeting connectivity | DNS, certificates, meeting URL validity, user permissions |
| Teams sign-in | Licence assignment, service status, auth configuration |
| Teams presence | Presence status sync, Outlook integration |
| Teams calendar | Calendar sync between Teams and Exchange |
| Teams call quality | Recent call quality data for a specific user |
| Teams device provisioning | Resource account configuration, licence assignment |
How to use diagnostics
- Go to M365 admin center → Help & Support → type your issue
- Select the relevant diagnostic test (or the system suggests one)
- Enter the affected user’s email address
- The diagnostic runs automated checks and returns results with recommendations
Scenario: Jaylen uses diagnostics for a sign-in issue
A new hire at RemoteFirst can’t sign in to Teams. Jaylen runs the “Teams sign-in” diagnostic:
Input: newhire@remotefirst.com
Results:
- ✅ User exists in Entra ID
- ✅ Teams service is healthy
- ❌ No Teams licence assigned — user has an E1 licence but Teams isn’t enabled
- ✅ Authentication configuration is correct
Fix: Assign the Teams licence. Problem solved in 2 minutes instead of 30 minutes of manual investigation.
Client health in the admin center
Teams admin center → Teams devices → Health (for managed devices)
For organisation-wide client health:
- Client version distribution — how many users are on which version
- Client errors — aggregated error patterns
- Update compliance — are users on the latest version?
Troubleshooting installation and update issues
| Issue | Likely Cause | Fix |
|---|---|---|
| Teams won’t install | Insufficient permissions, antivirus blocking | Run as admin, add Teams to AV exclusions |
| Updates stuck | Corrupted update cache | Clear update cache, reinstall |
| New Teams won’t activate | Update policy set to “Not enabled” | Change update policy to allow new Teams |
| Teams crashes on launch | Corrupted cache or conflicting software | Clear cache, check GPU drivers, disable hardware acceleration |
| Teams runs slowly | Too many cached conversations, old hardware | Clear cache, check system requirements |
🎬 Video walkthrough
Flashcards
Knowledge Check
VP Rivera at RemoteFirst reports that Teams freezes every time she joins a meeting. Jaylen suspects corrupted local data. What should he try FIRST?
A new hire at RemoteFirst can't sign in to Teams. Jaylen wants to quickly identify the cause. What should he use?
Next up: Copilot & Meeting Troubleshooting — the final module: troubleshooting Copilot and AI features, sign-in issues, and meeting join problems.