> 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/api-versioning.md).

# API versioning

IDlayr versions the public API at the **major level only** — `/v1/`, `/v2/`, etc. The version sits in the URL path; there is no header- or content-type-based version negotiation. A major bump only happens when a breaking change to the API contract is unavoidable.

## What's a breaking change

The version applies to the **API contract** — the shape of requests and responses, the set of endpoints, the meaning of `error_code` values. A change is breaking only if a valid integration against the prior major could stop working as a result. Additive changes are not.

| Breaking — requires a new major                                       | Non-breaking — ships within the current major                 |
| --------------------------------------------------------------------- | ------------------------------------------------------------- |
| Removing or renaming a field on a response                            | Adding any new field to a response                            |
| Adding a new required field to a request                              | Adding a new optional field to a request                      |
| Changing the type of an existing field                                | Adding a new endpoint                                         |
| Removing an endpoint                                                  | Adding a new optional query parameter                         |
| Changing the semantics of any field                                   | Adding a new `error_code` value                               |
| Tightening validation in a way that rejects previously-accepted input | Loosening validation, or rejecting previously-malformed input |

## Implications for your integration

Two practical rules follow. Both are about staying robust to additive change.

**Avoid pinning to the payload shape.** We strongly discourage pinning client code to a specific payload shape — IDlayr may add new fields to responses or callbacks at any time within the same major. Tolerate fields you don't recognise; parse what you need and ignore the rest. Code generators with strict modes (rejecting unknown fields) tend to break on additive platform changes — configure them to tolerate unknown fields where possible.

**Tolerate new `error_code` values.** The catalogue grows additively within a major. Switch on the codes your integration handles explicitly; route unknown codes to a generic-error branch rather than crashing.

## API versioning is separate from SDK versioning

The HTTP API version (`/v1/`) and the mobile SDK version (e.g. `IDlayrKit 2.4.1`) are independent. Major bumps are scheduled independently; an SDK upgrade does not change the API contract, and an API major bump does not force an SDK upgrade. See [SDK versioning](/get-started/sdks/versioning.md) for the SDK side.

## URL design

Within a major, IDlayr applies a few URL conventions consistently:

* **Resource-based.** URLs name resources (`/v1/sim-swap/checks/{check_id}`), not actions (`/v1/check-sim`).
* **Family namespaces.** Products that share a mechanism are grouped under a single prefix — for example, `/v1/number-verification/secure-sna-checks/`, `…/reverse-sms-checks/`, `…/discovery-checks/`. This mirrors CAMARA's convention for related products and lets the reference docs present the family as one section.
* **Kebab-case** for path segments; **snake\_case** for JSON field names.

## Legacy v0.x

**New integrations should use v1.** The legacy v0.1 and v0.2 endpoints are closed to new adopters — they're maintained for existing integrations and in-flight migrations only, not as a starting point.

Existing v0.x integrations remain operational on **security-only maintenance** — limited to vulnerabilities flagged by IDlayr's internal SAST tooling or Vanta findings. No new features land on v0.x, and no functional bug fixes outside that scope.

For migration mechanics — the rename map, the per-product breaking changes, suggested order — see the [v0.x to v1 migration guide](/guides/migration.md).


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