Do these 3 things before closing this tab:
1Repair Windows errors before they cause bigger problems2Fix the driver behind crashes, sound loss and screen glitches3Clear out junk files and repair common Windows errorsLeague of Legends Error 004 means a patch failed; it does not identify one specific cause. Riot’s guidance points to the client, permissions, installation-drive storage, firewall or network access, and game files. Work through the checks below from least disruptive to most disruptive, retrying the patch after each relevant change.
What League of Legends Error 004 means
The message reads: “Patching failed and we’re not sure why. Please restart the client to try patching again. (Error code 004).” Riot says the error occurs when League fails during a patch. Possible contributing issues include Riot Client permissions, insufficient available storage on the game’s installation drive, or trouble reaching the network services needed to download and install the update. The code alone does not show which one is responsible. (Riot Games Player Support, Error Code 004, July 15, 2026; Riot error-code reference)
Try these fixes in order
After a step that changes something, reopen or retry the patch so you can tell whether it helped. Riot does not publish a required free-space amount or a success rate for these fixes.
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Fully restart Riot Client
Close the Riot Client, including its system-tray instance, then reopen it and try patching again. A window close alone may leave the client running in the background.
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Restart your PC
Restart Windows, then launch Riot Client and retry. Riot notes that a restart can clear temporary issues, release locked files, and finish pending Windows updates.
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Run Riot Client as administrator
Permissions can prevent patch files from being applied. Use Riot’s platform-specific instructions to run the client with administrator privileges: Riot’s Error Code 004 guide.
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Check free space on the installation drive
Find the drive where League is installed and check its available space. If it is nearly full, free some space and restart the client before retrying. Riot does not state a numeric minimum for resolving Error 004, so there is no supported basis for a fixed GB target.
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Check firewall access
A firewall may block Riot Client communications with Riot’s servers. Review Riot’s firewall guidance and make sure the required game and client connections are allowed. Do not leave your firewall disabled as a workaround: Riot firewall and connection guidance.
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Troubleshoot your connection if the patch cannot download
Use Riot’s PC Connection Troubleshooting Guide if the client cannot reach the network or the download will not start. If you are on Wi-Fi, testing an existing wired Ethernet connection may improve patch download speed and quality; it is an optional diagnostic, not a guaranteed Error 004 fix. Riot’s patching guide also discusses public DNS as a possible option when a launcher does not start downloading, but it is not a universal remedy: Riot installing and patching guide.
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Run League’s full repair
Open League of Legends, select the gear icon, then choose Initiate Full Repair. Riot’s general patching guidance says the process may take from five minutes to over 30 minutes, depending on how many files need repair. This checks and repairs game files; it is distinct from reinstalling and is not an Error 004-specific success guarantee. (Riot installing and patching guide)
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Reinstall League if the earlier steps fail
Reinstalling is a later troubleshooting step because it takes more time than restarting, checking settings, or repairing files. Follow Riot’s uninstall and reinstall instructions: Riot’s Error Code 004 guide.
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Send Riot Player Support a ticket with logs
If Error 004 remains after the troubleshooting steps, submit a ticket to Riot Player Support and attach the requested logs. Logs can give support more detail than the error code alone. Use the support link and log instructions in Riot’s Error Code 004 guide.
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When the code keeps returning
Do not assume repeated Error 004 messages prove a particular cause. Riot’s cited guidance does not give a fix-success percentage or a universal disk-space threshold. If restarting, permissions, storage, connection checks, and repair do not resolve the patch, use Riot’s later reinstall and support steps rather than relying on an unsupported diagnosis.
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