If you're using a Developer-signed IPA, you'll need your device's UDID before signing. UDID stands for Unique Device Identifier — a 40-character hex string that uniquely identifies a single iPhone or iPad. Apple uses it to control which devices a Developer or Ad-Hoc certificate can install on.

Method 1: get.udid.io (no computer needed, easiest)

This is the fastest way and the one most signing services recommend:

  1. Open https://get.udid.io in Safari on your iPhone (not Chrome — Safari is required for OTA profile install).
  2. Tap "Tap to find UDID" and "Allow" when iOS asks to download a configuration profile.
  3. Open Settings when prompted, tap "Profile Downloaded" → "Install".
  4. You'll be redirected back to the site showing your UDID, IMEI, and serial.
  5. Copy the UDID and send it to your signing provider.

After getting your UDID, remove the configuration profile from Settings → General → VPN & Device Management — it's no longer needed.

Method 2: Finder (Mac) or iTunes (Windows)

Connect your iPhone to a computer via cable, then:

  • macOS Catalina or later: open Finder → click your device in the sidebar → click the device name area below the iPhone image. The serial number toggles to UDID on each click.
  • Windows / older Mac: open iTunes → click the device → click the serial number to cycle through serial / UDID / ECID.

This method requires no profile install and is the most "official" route.

Method 3: Xcode (developers)

If you have Xcode installed:

  1. Plug in your device.
  2. Open Xcode → Window → Devices and Simulators.
  3. Select your device — the UDID is shown under "Identifier".

UDID vs IDFA vs IDFV — quick clarification

Apple has multiple identifiers; only UDID matters for signing:

  • UDID — hardware-level, fixed, used by Apple for cert provisioning
  • IDFA — Identifier for Advertisers, user-resettable, for ad attribution
  • IDFV — Identifier for Vendor, per-app-developer, for analytics

When a signing service asks for your "device ID", they always mean UDID.

Privacy note

Your UDID is a permanent device fingerprint. Only share it with signing providers you trust. A reputable signing service uses your UDID solely to add it to the provisioning profile and discards it after signing — it shouldn't be retained beyond that.