Before you can register your ECID, you must extract it from your device. You can use several methods depending on your operating system and available tools. Method 1: Using Finder or iTunes (Mac and Windows)
This error occurs when you mistakenly paste the ECID instead of the UDID into the Apple Developer portal’s device registration form. Remember: the developer portal accepts only the 40‑character UDID, not the raw ECID. Obtain your UDID via Xcode, Finder, or iTunes as described above.
If you prefer an all-in-one device management suite, tools like 3uTools (Windows) or iMazing (Mac/Windows) display your ECID on their primary dashboard. Open the software and connect your device. Look at the main device details screen. Find the field labeled .
Locate the field and click it once; it will change to the UDID .
field twice. It will cycle through the UDID and then display your On Mac (via Finder): Connect your device and open
Open (macOS Catalina or later) or iTunes (Windows/earlier macOS). Click on the device icon to open the Summary tab.
Apple buries this info, but as noted by iDownloadBlog , it’s easy to uncover using a computer:
Platforms like or similar utilities require you to register your ECID to unlock features for your specific hardware.