Understanding & Using Identifier (IMSI) Rotation
The IMSI is a unique number assigned by your mobile carrier when you sign up for service. It lives on your SIM card and typically never changes. Every time your phone connects to the network, it shares this identifier, allowing anyone with network access to track everywhere you’ve been and to build a complete picture of your life over time.
Previously, this feature was only available within our Obscura service, but due to strong interest from our customers, our team has been working hard to make it available to more people.
What Is Identifier Rotation?
Cape’s Identifier Rotation automatically rotates your IMSI on a daily basis, and also allows you to change your IMSI on-demand at the tap of a button within the Cape app. By making your IMSI ephemeral, Cape protects you from tracking over time. Your daily behavioral patterns, like your commute to work, gym routine, and more, would be scattered among constantly changing IMSIs.
Rotating the IMSI also strengthens existing Cape protections like Network Lock, which was designed to defend against SS7 and other signaling attacks that allow remote location tracking and interception of phone calls and texts. Daily IMSI rotation effectively nullifies this attack, as the adversary would be targeting an IMSI that you no longer use.
How Does IMSI Rotation Work?
To accomplish this, Cape provides each subscriber with a set of seven unique IMSI values per week from a large pool of reserved numbers. Once Identifier Rotation is enabled, your phone's IMSI will automatically cycle to a different one every 24 hours, giving you a completely new network identity each day.
After seven days, your old set is retired, and you’ll be assigned a new set of seven IMSIs for the following week. IMSI value sets come from a shared pool that cycles through different Cape customers week after week. This means that each IMSI value has associated with it a tangled history of activity, making it much harder for anyone to track you.
You can also choose to rotate your IMSI manually from the app, which you may use in high-risk moments like crossing a border or attending a protest. When you manually rotate, your device simply cycles to the next IMSI in your weekly set.
Device Compatibility
While Cape's cellular service works on a wide range of devices, Identifier (IMSI) Rotation requires specific hardware capabilities.
| Device Family | IMSI Rotation Status |
|---|---|
|
Google Pixel (Pixel 4 and newer)
|
✅ Supported Fully compatible (Stock Android & GrapheneOS).
|
|
Apple iPhone (XS through 17)
|
✅ Supported |
|
Samsung Galaxy (All Models)
|
❌ Not Available Cape Service works, but IMSI Rotation is not yet supported.
|
|
Motorola (All Models)
|
❌ Not Available Cape Service works, but IMSI Rotation is not yet supported.
|
General Requirements
In addition to the specific model requirements above, your device must meet the two standard requirements for Cape service:
- It must be eSIM compatible.
- It must be carrier-unlocked.
How to check if your device is unlocked →
See our full list of Cape compatible devices here →
How to Start Using Identifier Rotation
Identifier Rotation is now available as an Experimental Feature within the Cape app.
If you’re a Cape subscriber, here’s how to turn it on:
- Update the Cape app to the latest version
- Enable Feature: Open the Cape app and go to Account → Features. Select "Identifier Rotation" and enable it.
- Upgrade eSIM: You'll be prompted to activate a new eSIM with ID rotation capability.
-
Prep Your Phone: Follow the steps shown in the app:
- Turn ON Wi-Fi.
- Turn OFF your existing Cape eSIM in your phone settings.
- Finalize: After your upgraded eSIM is activated, go back to the app and toggle IMSI ON. You should be set.
Note: During each rotation, your modem will reboot, and your phone will briefly lose service for about 30–60 seconds. You’ll be able to see the current IMSI value of your device in the app.
How to Verify Your IMSI
On Android:
Dial *#*#4636#*#*, select Phone Information, and check your IMSI.
Or search for “Cape Roaming” or "SIM Toolkit" on your device (it will look like an additional app). Then tap Cape Roaming → Read IMSI.
On iPhone:
Go to Settings → Cellular → [Your Cape eSIM] → SIM Applications → Cape Roaming and select "Read IMSI".
Important Notes
- GrapheneOS: IMSI Rotation works with GrapheneOS.
- Changing the Rotation Schedule: Right now, the feature is automated to rotate every 24 hours from the moment you enable it. If you want to change the scheduled rotation time, you can just toggle Identifier Rotation off, and toggle it back on. The new 24-hour cadence will re-start from the moment you toggle the feature back on.
- International Usage: IMSI rotation can be used while travelling international.