UDID Checker

Read the UDID of the iPhone or iPad you are holding, without a Mac and without handing it to a device list somebody else owns. This UDID checker verifies the signature your device puts on its answer, shows the identifier once, and stores nothing anywhere — no database, no cookie, no analytics.

How to use UDID Checker

  1. Open this page in Safari on the iPhone or iPad itself — iOS lets no other browser install the profile this needs.
  2. Tap “Get my UDID” and allow the one-time configuration profile to download.
  3. Open Settings, tap the “Profile Downloaded” row near the top, read what it says it will do, then tap Install.
  4. Safari reopens here with the UDID on screen, checked against the signature your device applied to it.
  5. Copy the value, then delete the profile from Settings → General → VPN & Device Management.

About UDID Checker

Registering a test device with Apple is a small job with an unforgiving failure mode. A development or ad-hoc provisioning profile is a signed list of the devices a build may run on, keyed by UDID, and an identifier that is wrong by a single character produces a build that simply refuses to install — with an error message that mentions none of it. So the number matters, and where it came from matters.

The awkward part is that reading it requires a round trip. Apple gives iOS no way to hand a UDID to a web page, so a browser-based checker must use the over-the-air profile flow: Safari installs a small profile, the device signs the attributes that profile asked for, and it posts them once to the URL inside it. Most UDID sites take that response and pull the value out with a regular expression, without ever checking the signature the device went to the trouble of applying — and quite a few of them exist to accumulate the resulting list, because a UDID paired with an email address is what a resigning service needs to sell somebody a sideloaded app. That is the part worth caring about: not that a number passed through a web server, but whether anybody kept it.

This one is built to make that round trip as small as it can be. The profile requests three attributes rather than the seven the format allows, and the exact bytes are readable on the page before anything is installed. The signed response is verified properly — the content digest is recomputed and compared against the digest the device signed, and the signature is checked with the certificate carried inside the message — so a value that cannot be authenticated is labelled as such instead of being shown as though it were confirmed. Whichever route the reading comes back on, the page strips it from the address bar the moment it arrives, so it never reaches browser history, and nothing is written down at either end. There is also a private-link mode that returns it in the URL fragment, the part browsers never transmit, so it reaches no request log at all — offered rather than forced, because it depends on the device preserving that part of the address through the hand-off and Apple documents no guarantee that it will.

None of which beats a cable. If the device is in front of a computer, Finder, Xcode or the Apple Devices app will show the same identifier with nothing installed and nothing transmitted, and those steps are on this page too — a tool that only tells you about the method that needs it is not being straight with you. What is worth remembering either way is that a UDID is not a secret: it identifies a device, so it should not be posted publicly, but knowing one grants no access to the phone, its data or its Apple account.

Frequently asked questions

What is a UDID, and how is it different from a serial number?

The Unique Device Identifier is a 40-character hexadecimal string on hardware older than the iPhone XS, and an 8-character block, a hyphen and a 16-character block on everything since — an iPhone 15 always reports the second form. It is what a provisioning profile lists to decide which devices a build may run on. A serial number is shorter, printed on the box, and used for warranty and support; Apple’s device registration will not accept one in place of a UDID.

Why does a website need to install a profile just to read it?

Because iOS exposes no JavaScript API for the UDID and never has. Apple removed the ability for apps to read it in 2013, and web pages never had it. The only route Apple provides is the over-the-air profile flow — the device signs its own attributes and posts them back — so every site that shows you a UDID in a browser works this way, whether it explains that or not.

Is installing the profile safe?

This one asks for three values and nothing else: the UDID, the model identifier and the iOS build number. It requests no serial number, IMEI, MAC address or device name, sets up no VPN, installs no certificate and enrols nothing — and you can read the exact bytes on the page before you install it. The general rule is worth learning anyway: read the install sheet iOS shows you, and cancel if it mentions a VPN, an MDM enrolment, a Wi-Fi network or a certificate to trust.

Why does iOS say the profile is “Not Signed” in red?

That label means the profile carries no cryptographic signature from a paid Apple certificate. It is a statement about provenance, not behavior — it says nothing at all about what the profile does. A signed profile that enrols your device in someone’s MDM is far more dangerous than an unsigned one that reads three values and disappears. Judge the payload listed on the install sheet, not the badge above it.

Why does the install sheet say “Device Enrolment Challenge”?

Because the payload that asks a device for its UDID is the same one an MDM server uses for the opening handshake of an enrolment, so iOS names it that way in both cases. What differs is the server’s reply: an MDM server answers with an enrolment profile that stays on the device, while this answers with a redirect and installs nothing. The full list under Contains should read exactly two lines — Device Enrolment Challenge and Consent Notice. Anything more than that, on any site, is worth cancelling over.

Is my UDID stored on the server?

No. There is no database, no cache and no cookie holding it. The value passes through the server between reading the request and writing the redirect that sends you back here, and the page then removes it from the address bar so it stays out of your browser history too. On the standard route it does appear once in the web host’s request log, the way it does on every service of this kind; private-link mode hands it back in the URL fragment — the part browsers never transmit — so it reaches no log at all, at the cost of depending on your device preserving that part of the address. Both routes are offered and neither stores anything.

Can I get the UDID without installing anything at all?

Yes, and it is the better option whenever a computer is to hand. On a Mac, connect the device, open Finder, select it in the sidebar and click the grey line under its name until the UDID appears. In Xcode, use Window → Devices and Simulators and read the Identifier field. On Windows, the Apple Devices app shows it when you click the serial number. Nothing is installed and nothing is transmitted on any of those routes.

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