> For the complete documentation index, see [llms.txt](https://docs.idlayr.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.idlayr.com/get-started/concepts/access-models.md).

# API access models

IDlayr products fall into two access models. The distinction determines whether you need a mobile SDK on the device, whether the end user needs to be on cellular data, and what credentials your backend needs.

## Device APIs (device-to-backend)

The end user's device participates in the verification flow over the cellular data path, and the IDlayr **mobile SDK is required** to pin the request to the cellular interface and observe the carrier's response. These products require:

* The mobile SDK (iOS — `IDlayrKit`; Android — `idlayr-sdk-android`).
* A Cloudsmith entitlement token to fetch the SDK at build time.
* An OAuth2 access token minted by your backend and passed to the SDK at runtime.
* An active cellular data connection on the device at the moment of verification — Wi-Fi breaks the trust path.

**Products in this category:** Secure SNA, Discovery.

Both use Number Verification 1.0 (NV 1.0), which depends on the carrier attributing the active data session to a phone number. NV 2.1 — which uses carrier entitlement servers to widen coverage — is in active rollout; endpoints are tagged with their NV version on the API reference.

## Backend APIs (backend-to-backend)

Server-to-server only. Your backend calls the IDlayr API and receives a result. The end user's device may participate in the user-facing UX (in Reverse SMS the user sends an SMS), but **there is no IDlayr SDK on the device** — no Cloudsmith entitlement, no platform-specific code.

* No IDlayr mobile SDK.
* No Cloudsmith entitlement token.
* No cellular-data constraint.
* Works from any channel — native app, mobile web, desktop, IVR, server-only flows.

**Products in this category:**

* **SIM Swap** and **Eligibility** — pure backend products with no device-side step.
* **Reverse SMS** — backend integration; the device-side step is your app opening the native SMS composer via a standard `sms:` URL scheme. No SDK, no IDlayr code on the device.

## When you need both

Combining a device API (e.g. Secure SNA for device-and-number trust) with a backend API (e.g. SIM Swap to detect a recent SIM change) closes attack vectors neither product can close alone.


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