# Webhooks Overview

Product: Client Account API
Guides follow API reference 0.3.0 and event reference 0.2.0.
Canonical page: https://docs.sandbox.axiym.io/client-account-api/webhooks/overview

Webhooks let Axiym notify your service when Client Account API resources
change. Use webhooks to track client onboarding and availability, deposits,
withdrawals, conversions, registered external accounts, and posted Axiym
account balance movements without continuously polling every resource.

## How it works

1. **Register an HTTPS endpoint.** Create a subscription with
   `POST /webhooks/subscriptions`. See
   [Registration and Management](/client-account-api/webhooks/registration-management).
2. **Receive events.** Axiym sends an HTTP `POST` with a JSON event envelope to
   each active subscription endpoint.
3. **Verify the signature.** Every delivery is signed with Ed25519. Verify it
   before trusting the payload. See
   [Verifying Webhook Signatures](/client-account-api/webhooks/verifying-signatures).
4. **Acknowledge delivery.** Return a `2xx` response after your system has
   safely persisted or queued the event.

Webhook subscriptions are endpoint-level. The current API does not expose
per-event subscription filters. An active subscription receives every event
emitted for your partnership, including event types outside this Client Account API
reference. Ignore unknown event types safely. Validate the event type and
payload shape before routing it, and correlate resource identifiers with
your records.

## Event catalogue

The Client Account API emits events for clients, deposits, withdrawals, conversions,
registered external accounts, and Axiym accounts. External-account events use the
`destination.*` prefix and describe their review and availability.
See [Events](/client-account-api/webhooks/events) for event names, the shared webhook
envelope, and the fields delivered in `data`. Use `client.activated` for client
availability; `client.onboarding-finished` is a deprecated legacy activation
event.

## Route events to the client

Subscriptions belong to your partnership. Client resource events include
`data.clientId`; use it with your stored resource identifiers to route the
event and retrieve current state through `/clients/{clientId}/...`.

Dispatch by event `type` before expecting client fields. The `subscription.test`
event has no `clientId`, and events from other products may have a different
payload. Handle test deliveries separately and ignore unknown event types safely.

## Delivery and retries

Axiym treats any `2xx` response as accepted. If the endpoint returns a non-2xx
status or the connection fails, Axiym retries the delivery.

* Up to 4 attempts per event: the initial delivery plus 3 retries.
* Exponential backoff between retries: about 1 second, then 2 seconds, then 4
  seconds.
* After the final attempt, the event is not delivered again automatically.

Deliveries can repeat or be missed if all attempts fail. Your receiver must be
idempotent and de-duplicate events by `id`. Do not rely on webhook delivery order as the only
source of state; fetch the resource from the API when you need the latest
authoritative state where available.

Keep handlers fast. A common pattern is to verify the signature, persist or
enqueue the event, return `2xx`, and process the business logic asynchronously.

## Security

Webhook deliveries include these headers:

| Header        | Description                                         |
| ------------- | --------------------------------------------------- |
| `X-Signature` | Base64 Ed25519 signature of the raw request body.   |
| `X-Key-Id`    | Public key identifier used to verify the signature. |
| `X-Algorithm` | Signature algorithm. Expected value: `Ed25519`.     |

Use `GET /webhooks/public-keys/{publicKeyId}` to retrieve the public key for
the `X-Key-Id` value. Signature verification must use the raw HTTP request body,
before JSON parsing or re-serialization.

**Source IP addresses.** The published contract does not define a source-IP
allowlist. Do not rely on fixed addresses; confirm any network restrictions
with Axiym for your environment.

## Related pages

* [Webhook Registration and Management](/client-account-api/webhooks/registration-management)
* [Verifying Webhook Signatures](/client-account-api/webhooks/verifying-signatures)
* [Events](/client-account-api/webhooks/events)