IS-0009 Fortnite

Error Code IS-0009 - Fortnite Fix Guide

📅 Published: 2026-02-05 🔄 Updated: 2026-02-05 👥 Reports: 0 ⚡ Severity: 🟢 Low

🎯 Quick Answer

Clear the Epic Games Launcher's web cache and verify Fortnite's installation files to resolve the IS-0009 connection and installation error.

SECTION 1: OVERVIEW

Error code IS-0009 is a connection and installation failure code in Fortnite. The error indicates a failure in the communication protocol between the Epic Games Launcher and its backend services or a corruption in the local installation manifest. This error occurs on Windows and macOS platforms. It manifests across all recent game client versions, particularly following major content updates or launcher patches. The error frequency is classified as occasional, with spikes correlating with update deployments. Severity is high, as it prevents the game from launching or updating, rendering it unplayable. The exact error message presented is "Error code: IS-0009". The error persists even after attempts to verify game files or reinstall the Epic Games Launcher, indicating a deeper configuration or cache issue.

SECTION 2: SYMPTOMS

The Epic Games Launcher displays a modal dialog box containing the text "Error code: IS-0009". This occurs during the initial game launch sequence or when attempting to install a game update. The launcher fails to progress beyond the initial handshake with the game service. The game process either terminates immediately or fails to spawn. Clicking the "Verify" function for the game installation within the launcher triggers the same error message, preventing the repair operation. Uninstalling and reinstalling the Epic Games Launcher does not resolve the issue, as the underlying corrupted data persists in shared system directories.

SECTION 3: COMMON CAUSES

Category: Configuration Error Specific technical explanation: Corrupted web cache and data files within the Epic Games Launcher's %LOCALAPPDATA% directory. The launcher stores session tokens, CDN mappings, and installation manifests in this cache. Corruption prevents proper service communication. Why this causes the problem: The launcher cannot validate its state or retrieve correct installation metadata, triggering the IS-0009 failure. Category: Software Conflict Specific technical explanation: Overly restrictive settings in security software (antivirus, firewall) or Windows Defender Controlled Folder Access. These block the EpicGamesLauncher.exe or FortniteClient-Win64-Shipping.exe from writing necessary files. Why this causes the problem: The installation or update process is interrupted when critical files cannot be created or modified, resulting in a failed state. Category: Network Problem Specific technical explanation: DNS cache poisoning or stale entries pointing to outdated Epic Games content delivery network (CDN) addresses. The system resolves hostnames to invalid IPs. Why this causes the problem: The launcher cannot connect to the correct servers to download manifests or verify file integrity, causing the handshake to fail. Category: Configuration Error Specific technical explanation: Damaged or incorrect registry entries for the Epic Games Launcher under HKEY_CURRENT_USER\Software\Epic Games\EpicGamesLauncher. This includes invalid installation paths or security descriptors. Why this causes the problem: The launcher reads erroneous configuration data on startup, leading to pathing errors and service communication failures. Category: Game Bug Specific technical explanation: A known issue with specific versions of the Epic Games Launcher where the webcache_4430 folder becomes locked or generates invalid JSON state files. Why this causes the problem: The launcher's internal browser engine, used for authentication and store functionality, cannot initialize, halting the entire launch sequence. Category: Hardware Issue Specific technical explanation: Failing storage drive (HDD/SSD) with bad sectors where the Epic Games Launcher or Fortnite is installed. This causes file corruption during read/write operations. Why this causes the problem: Essential game files or launcher data become partially written or unreadable, breaking the installation's integrity.

SECTION 4: SOLUTIONS

Solution 1: Clear Epic Games Launcher Cache and Verify

Difficulty: Easy Time Required: 10 minutes Success Rate: High Prerequisites: None Steps:

Completely exit the Epic Games Launcher. Right-click its system tray icon and select "Exit".
Press Windows Key + R, type %LOCALAPPDATA%, and press Enter to open the Local AppData folder.
Locate and open the EpicGamesLauncher folder.
Delete the Saved folder within the EpicGamesLauncher directory.
Navigate back to %LOCALAPPDATA%, open the EpicGamesLauncher folder again, and then open the Saved folder (a new one will have been created).
Delete the webcache_4430 folder and the webcache_4430.sqlite file if present.
Restart your computer.
Launch the Epic Games Launcher as an administrator (right-click, "Run as administrator").
Navigate to your Fortnite library, click the three dots (...) under the game, and select "Verify".

Technical Explanation: This forces the launcher to rebuild its local configuration, web cache, and installation state from scratch, eliminating corrupted data that causes the IS-0009 handshake failure. Verification: The verification process completes without error, and the Fortnite "Launch" button becomes available and functional.

Solution 2: Flush DNS and Renew Network Configuration

Difficulty: Easy Time Required: 5 minutes Success Rate: Medium Prerequisites: Administrator access required Steps:

Press Windows Key, type "cmd", right-click "Command Prompt", and select "Run as administrator".
Execute the command: ipconfig /flushdns
Execute the command: ipconfig /registerdns
Execute the command: ipconfig /release
Execute the command: ipconfig /renew
Execute the command: netsh winsock reset catalog
Execute the command: netsh int ipv4 reset reset.log
Close the Command Prompt and restart your computer.

Technical Explanation: This clears local DNS caches that may contain outdated records for Epic Games servers and resets the Windows socket layer to a clean state, removing network stack corruption. Verification: After restart, other network applications function normally and the Epic Games Launcher can successfully verify or update Fortnite.

Solution 3: Configure Antivirus and Firewall Exceptions

Difficulty: Medium Time Required: 15 minutes Success Rate: High Prerequisites: Knowledge of installed security software Steps:

Open Windows Security by searching for "Virus & threat protection".
Click "Manage settings" under "Virus & threat protection settings".
Scroll to "Exclusions" and click "Add or remove exclusions".
Add the following folder exclusions:

- C:\Program Files\Epic Games (or your custom install directory) - %LOCALAPPDATA%\EpicGamesLauncher - %PROGRAMDATA%\Epic

Navigate to "Firewall & network protection" in Windows Security.
Click "Allow an app through firewall".
Click "Change settings", then "Allow another app...".
Browse and add EpicGamesLauncher.exe (typically in C:\Program Files (x86)\Epic Games\Launcher\Portal\Binaries\Win64) and FortniteClient-Win64-Shipping.exe (in your Fortnite Binaries\Win64 folder).
Repeat for any third-party antivirus software, adding the same folders and executables to its allow list.
Restart the Epic Games Launcher.

Technical Explanation: This prevents security software from intercepting or blocking file operations and network packets essential for the launcher's update and verification services. Verification: The launcher performs file operations (verifying, updating) without triggering security pop-ups and the IS-0009 error does not recur.

Solution 4: Perform a Clean Reinstall of Epic Games Launcher

Difficulty: Medium Time Required: 20 minutes Success Rate: High Prerequisites: Administrator access required Steps:

Uninstall the Epic Games Launcher via Windows Settings > Apps > Apps & features.
Press Windows Key + R, type %LOCALAPPDATA%, press Enter, and delete the entire EpicGamesLauncher folder.
Press Windows Key + R, type %PROGRAMDATA%, press Enter, and delete the Epic folder.
Press Windows Key + R, type regedit, and press Enter to open the Registry Editor. Warning: Editing the registry incorrectly can damage your system.
Navigate to HKEY_CURRENT_USER\Software\ and delete the Epic Games key.
Navigate to HKEY_LOCAL_MACHINE\SOFTWARE\ and delete the Epic Games key (if present).
Restart your computer.
Download the latest Epic Games Launcher installer from the official Epic Games website.
Right-click the installer and select "Run as administrator" to install.
Log in and attempt to verify or launch Fortnite.

Technical Explanation: This removes all persistent launcher data, registry settings, and configuration files, ensuring a completely fresh state without legacy corruption. Verification: A new installation completes successfully, and Fortnite can be verified or launched from the fresh launcher instance.

Solution 5: Run System File and Storage Health Checks

Difficulty: Advanced Time Required: 30 minutes Success Rate: Medium Prerequisites: Administrator access required, patience for scans to complete Steps:

Press Windows Key, type "cmd", right-click "Command Prompt", select "Run as administrator".
Execute the command: sfc /scannow and wait for completion.
To check disk health, execute: chkdsk C: /f (replace C: with the drive letter where Fortnite is installed). You will be prompted to schedule the scan for the next restart. Type Y and restart your computer.
After restarting and completing the disk check, open PowerShell as Administrator.
Execute the command: DISM /Online /Cleanup-Image /RestoreHealth
Allow the Deployment Image Servicing and Management tool to complete.
Restart your computer once more.

Technical Explanation: The System File Checker (sfc) and DISM tools repair corrupted Windows system files that may interfere with application services. Chkdsk identifies and marks bad sectors on the storage drive, preventing data corruption. Verification: The system scans report no integrity violations or successfully repair them. General system stability improves, and the Epic Games Launcher operates without file access errors.

SECTION 5: PREVENTION

Prevent IS-0009 recurrence by maintaining a consistent update schedule for the Epic Games Launcher. Configure Windows Update to install updates automatically. Perform a monthly clearing of the Epic Games Launcher web cache by deleting the %LOCALAPPDATA%\EpicGamesLauncher\Saved\webcache_4430 folder with the launcher closed. Add Epic Games directories to security software exclusion lists permanently. Monitor storage drive health using built-in tools like chkdsk or manufacturer utilities quarterly. Avoid interrupting game updates or launcher downloads, as this is a primary cause of manifest corruption. Ensure stable power and network connectivity during all patching operations.

SECTION 6: WHEN TO CONTACT SUPPORT

Contact Epic Games Support if all documented solutions fail and the error persists across multiple system restarts and a clean Windows user profile. Required diagnostic information includes the Epic Games Launcher.log located in %LOCALAPPDATA%\EpicGamesLauncher\Saved\Logs and a DXDiag report. Provide full system specifications, including Windows version, GPU driver version, and the exact timing of the error. Official support channels are accessible via the Epic Games Help Center website. Do not contact support before completing the cache clearance and clean reinstallation procedures, as these resolve the majority of cases.