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League of Legends error

d3dx9_43.dll is missing: a DirectX file Windows hasn't installed yet

League clientWindows

The message

The program can't start because d3dx9_43.dll is missing from your computer.

What it means

A DirectX file League needs isn't on the PC yet, so the match won't start. Riot sees it mostly on new computers.

What to try first

Run Windows Update until it has nothing left to install, then restart and launch League.

Is it you or Riot? If lots of players are hitting this at once, it's probably the servers. Check League server status before you start reinstalling things.

Why a new PC gets this

The DLL named in the message, d3dx9_43.dll, is part of DirectX. Riot's error table says the error turns up mostly on new computers and stops players from starting a match. Its explanation is simple: Windows Update delivers the file, and a fresh PC often hasn't run through all of its updates yet.

How to fix it

  1. Finish Windows Update. Open Settings, then Windows Update (on Windows 10 it's inside Update & Security), and keep installing and restarting until there's nothing left. Then launch League.
  2. Install the file by hand. If updates don't bring it in, Riot's fallback is Microsoft's DirectX End-User Runtime Web Installer. Get it from Microsoft's own download site and run it, then restart before you queue again.

If League then fails with a different graphics message, the Unknown DirectX error page is the next stop.

Other wordings of the same error

  • d3dx9_43.dll is missing
  • d3dx9_43.dll missing League
  • d3dx9_43.dll not found
  • The program can't start because d3dx9_43.dll is missing

Source: Riot Games Player Support, League Error Codes and Solutions, updated May 19, 2025. Riot's steps are paraphrased here, not copied; checked September 25, 2026.