An IPA file is the standard package format for iOS apps. Unlike Android, iOS doesn’t let you install IPAs by simply tapping them — every IPA must be cryptographically signed with a valid Apple Developer certificate before iOS will accept it.

Why You Need a Signing Certificate

iOS enforces mandatory code signing at the kernel level. When you tap an app icon, the OS verifies the app’s cryptographic signature before executing a single line of code. A missing or invalid signature produces an immediate rejection.

To sign an IPA, you need a developer certificate (.p12 file) registered to your device’s UDID. CertDrop provides exactly this: an individual Apple Developer certificate tied to your specific device, valid for 360 days, for $12 USDT.

Finding your UDID: Open Safari on your iPhone and visit udid.tech. Your UDID will be displayed on the page after you install the temporary profile.

Three On-Device Signing Apps

With a paid developer certificate from CertDrop, you can sign and install IPA files directly on your iPhone — no Mac, no USB cable, no computer at all.

Feather

Feather is a modern, clean on-device signing app designed specifically for paid developer certificates. Import your .p12 file and certificate password, then install any IPA directly from the Files app. Simple, fast, and fully on-device.

- Platform: iOS only (no computer required)
- Best for: Straightforward installs, clean UI

ESign

ESign is one of the most widely used on-device signing apps. Supports .p12 certificate import and installs IPAs directly from your Files app. Well-established in the iOS sideloading community.

- Platform: iOS only (no computer required)
- Best for: Users who want a mature, widely-tested tool

Scarlet

Another popular on-device signer with a polished interface. Works the same way as Feather and ESign: import your CertDrop .p12 certificate, then tap to install IPA files from your Files app.

- Platform: iOS only (no computer required)
- Best for: Users who prefer Scarlet’s interface

Step-by-Step: Installing an IPA

1. Order your certificate — Go to certdrop.app, enter your UDID and email, pay $12 USDT. Your .p12 file and password are emailed within minutes.
2. Save your .p12 to Files — Long-press the attachment in your email, save to Files app.
3. Install a signing app — Download Feather, ESign, or Scarlet onto your iPhone.
4. Import your certificate — Open your signing app, tap "Import Certificate", browse to your .p12 file, enter your password.
5. Install your IPA — Save the IPA to Files app, open it in your signing app, tap Install.
6. Launch your app — The app appears on your home screen and opens immediately.

What UDID Is and How to Find It

UDID stands for Unique Device Identifier — a 25-character alphanumeric string that identifies your specific iPhone or iPad. Apple uses it to bind developer certificates to specific physical devices. Your UDID does not change unless you replace your device.

1. Open Safari on your iPhone
2. Go to udid.tech
3. Tap the button to download a configuration profile
4. Install the profile in Settings when prompted
5. Your UDID appears on the udid.tech page

How Signing Works

When a signing app processes your IPA, it replaces the existing signature with yours, embeds your provisioning profile (authorising your UDID), and cryptographically signs the binary with your private key. The result is an IPA that iOS recognises as trusted. The whole process takes a few seconds and happens entirely on your device.

Note on IPA sources: Stick to app-specific communities, developer GitHub pages, and sources with visible reputation. A tampered IPA can contain malicious code.