> ## Documentation Index
> Fetch the complete documentation index at: https://docs.bango.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Idempotency

> Avoiding accidental duplications

The Bango Subscriptions API supports **idempotency**. With idempotency, the API guarantees to return the same response given a duplicate request. This helps avoid accidental duplications, especially when creating a subscription.

For example, if you make an API request to create a subscription, and then make the same API request again, the response to the second request will be identical to the response to the first request. The second request does not create a new subscription.

To use idempotency, include the header `X-RequestIdentifier` in every API request. The header must have a **globally unique value**. This lets the Bango Subscriptions API identify repeated requests.