However, there is a crucial technical detail you need to understand before clicking any download links:

Always download directly from Apple’s official support portal. Ignore third-party sites promising “iTunes 13”, “iTunes 10.13.99”, or “iTunes for unsupported Macs.” They are vectors for malware.

Note: macOS version 10.13.99 does not exist as an official Apple release. The final version of macOS High Sierra is 10.13.6. This article addresses the user intent behind the search (finding the last compatible iTunes for older macOS versions) and corrects the version number while providing safe download solutions. Published by TechLegacy | Updated: 2026

| Error Message | Solution | |---------------|----------| | “iTunes requires macOS 10.13.6 or later” | Your OS is too old (e.g., 10.12 Sierra). You cannot install this version. Download iTunes 12.8.2 for Sierra instead. | | “A newer version of iTunes is already installed.” | You have a beta or corrupted version. Use AppCleaner to remove iTunes manually, then reboot and reinstall. | | “The installer encountered an error (code 2).” | Your System Integrity Protection (SIP) is blocking part of the install. Boot into Recovery Mode, disable SIP temporarily, install, then re-enable SIP. | | DMG won’t mount | Corrupt download. Delete the file, clear your browser cache, and re-download from Apple. | Finding “iTunes macOS 10.13.99 download” suggests you are committed to an older workflow. Here is a quick decision guide: