How to Configure TCP MSS in Windows via Regedit

This guide explains how to configure the Transmission Control Protocol Maximum Segment Size (TCP MSS) for a specific network adapter in Windows using the Registry Editor (Regedit). By identifying your network adapter’s unique interface identifier and adding the proper registry parameter, you can manage the maximum payload size of TCP packets, prevent packet fragmentation, and improve network stability across your connections.

Step 1: Identify the Network Adapter GUID

Before opening the Registry Editor, you must find the Globally Unique Identifier (GUID) of the target network adapter:

  1. Press Win + R, type powershell, and press Enter.

  2. Run the following command:

    Get-NetAdapter | Select-Object Name, InterfaceDescription, InterfaceGuid

  3. Locate your active network adapter and copy the value shown under InterfaceGuid (including the curly braces {}).

Step 2: Open the Registry Editor

  1. Press Win + R, type regedit, and press Enter.
  2. Click Yes if prompted by User Account Control (UAC).

Step 3: Navigate to the Interface Registry Key

In the Registry Editor address bar, navigate to the following path:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces

Expand the Interfaces folder to reveal a list of subkeys corresponding to your system’s network adapter GUIDs. Click on the subkey that matches the GUID you identified in Step 1.

Step 4: Configure the MSS Parameter

  1. Select the target GUID key in the left pane.
  2. In the right pane, right-click an empty area, select New, and choose DWORD (32-bit) Value.
  3. Name the new value MSS and press Enter.
  4. Double-click the newly created MSS entry.
  5. Under Base, select Decimal.
  6. In the Value data field, enter your desired segment size in bytes (for example, enter 1460 for standard Ethernet with a 1500 MTU, or 1452 for PPPoE connections).
  7. Click OK to save the value.

(Note: Windows derives the MSS automatically from the MTU if an MTU DWORD value is defined; setting MSS explicitly overrides this calculation for the specified interface.)

Step 5: Apply the Changes

To make the new configuration active:

  1. Close the Registry Editor.
  2. Disable and re-enable your network adapter via Network Connections (ncpa.cpl), or restart your computer.