The Client Server version mismatch League of Legends error is one of the most common issues players face after updates. It usually appears when you try to queue or log in, and it prevents you from playing entirely.

The good news? This error is almost always fixable.

In this guide, you’ll learn what causes the Client Server version mismatch League of Legends error, how to fix it step by step, and how to prevent it from happening again.

What is the Client Server version mismatch League of Legends error?

The Client Server version mismatch League of Legends error happens when your game client version does not match the version running on Riot’s servers.

This means:

• Your game is outdated, or
• The update didn’t install correctly, or
• Riot servers are on a different patch version

Because League of Legends is an online game, both client and server must match exactly. If they don’t, access is blocked.

Try these quick Client Server version mismatch League of Legends error fixes first

Before going into advanced solutions, try these simple steps:

• Restart the Riot Client
• Restart your PC
• Log out and log back in
• Check if the client updates automatically
• Close all Riot processes in Task Manager

In many cases, these steps alone fix the Client Server version mismatch League of Legends error.

How to fix the Client Server version mismatch League of Legends error (Advanced)

If the error continues, follow these solutions in order.

1. Force the client to update

Sometimes the client does not check for updates correctly.

1. Open Riot Client
2. Log out of your account
3. Close the client completely
4. Reopen and log back in

This forces a version check and update.

2. End all Riot processes

Background processes can block updates.

1. Press Ctrl + Shift + Esc
2. Find:
   • Riot Client
   • LeagueClient.exe
3. End all related tasks
4. Restart the client

3. Use Riot Repair Tool (formerly Hextech Repair Tool)

The Riot Repair Tool (RRT) is Riot’s official fix tool.

What it does:

• Repairs corrupted files
• Forces updates
• Fixes patch issues

How to use:

• Download the tool
  • Windows
  • MAC (ARM64)
  • MAC (INTEL)
• Select Force Repatch
• Run the repair

4. Run full repair from client

You can repair the game directly.

1. Open League Client
2. Click the Settings (gear icon)
3. Select Full Repair
4. Wait until it finishes

This ensures your files match the current server version.

5. Allow League of Legends Through Windows Defender Firewall

Sometimes the Client Server version mismatch League of Legends error happens because your firewall blocks the client from connecting properly.

1. Open Windows Security
2. Go to Firewall & network protection
3. Click Allow an app through firewall
4. Click Change settings
5. Find and allow:
   • Riot Client
   • League of Legends
6. Make sure both Private and Public boxes are checked
7. Click OK and restart your PC

This ensures your client can communicate with Riot servers without restrictions.

6. Reinstall League of Legends (Clean install)

If nothing works, do a clean reinstall.

1. Uninstall the game
2. Delete remaining Riot Games folders manually
3. Restart your PC
4. Install the game again

This removes any corrupted or outdated files causing the Client Server version mismatch League of Legends error.

7. Check Server Status

Sometimes the problem is not on your side. Check if Riot servers are:

• Updating
• Down
• Experiencing issues

If servers are mid-patch, you may need to wait. If everything is right, you will see a screen like that: 

8. Fix system time

Incorrect system time can break server communication.

• Enable automatic time sync
• Restart your computer

9. Disable VPN or Proxy

VPNs can cause region mismatch problems.

Turn off any VPN or proxy and try again.

10. Flush DNS Cache

Network issues can also cause mismatches.

1. Open Command Prompt
2. Run:
   • ipconfig /flushdns

How to prevent the Client Server version mismatch LoL error

To avoid the Client Server version mismatch League of Legends error in the future:

• Always let updates finish completely
• Avoid closing the client during patching
• Restart your client after updates
• Use repair tools occasionally
• Keep your system time correct