### How has client count changed across different Vault versions? ((#logic-improvements))

Client counts have been available via the usage metrics UI since Vault 1.6. We
have made continual improvements to the Vault client count computation logic
provided in the Vault UI and API. 

| Version | Interface | Accuracy improvement
| :-----: | --------- | --------------------
| 1.6     | N/A       | Introduced client counts as a metric
| 1.8     | All       | Eliminated wrapped tokens and control groups and counts active identity entities at usage instead of create time
| 1.9     | All       | Improved non-entity token tracking and local auth mount computation logic
| 1.10    | API       | Supported data export for unique clients contributing to the client count aggregate for a selected billing period
| 1.10    | UI        | Displayed clients per auth mount within a namespace
| 1.11    | API       | Supported unique client export for selected billing periods
| 1.11    | UI        | Displayed month over month calculations for client count

The latest GA version of the Vault binary always contains the most updated
version of the client count computation logic.

### How has the usage metric UI changed across different Vault versions? ((#ui-improvements))

| Version | UI improvement
| :-----: | -----------------------------
| 1.9     | The dashboard added the ability to export client count data for all namespaces and tabs for **Current month** and **Monthly history** that list the top ten namespaces by client count
| 1.10    | Added attribution of clients per authN mount to the **Current month** and **Monthly history** tabs
| 1.11    | Added the ability to view changes in client counts month over month, the running client total, and new monthly clients.

### Are there any known client count issues in the UI/API? ((#uiapi-ki))

**Yes**.

| Version | Client count issue
| :-----: | -----------------------------
| 1.9     | Billing period cannot be computed for start and end dates that fall in the middle of a month
| 1.10    | KMIP clients are not provided.
| 1.10    | Data on the **Current month** tab does not take the billing period into account.

### What happens to client count when I upgrade? ((#what-happens-at-upgrade))

**Vault will only reflect the number of active unique clients since the upgrade**.

We recommend upgrading **before** your next billing period begins so that the
usage metrics UI correctly reflects all clients for the current billing period.

<Warning heading="Time your upgrade appropriately">
  If your billing period falls on either side of a Vault upgrade, the compute
  logic may be different across the billing period, which will change client
  count results and create noisy data.
</Warning>

<Tabs>
  <Tab heading="Upgrading from Vault 1.8">
    Vault 1.9 introduced changes to non-entity token and local auth mount logic
    for client counting that affects anyone upgrading from v1.8 to a newer
    version:
    <ul>
      <li>
        Any <b>non-entity tokens</b> created before the upgrade will receive an
        artificial client ID the next time the token authenticates to Vault. As
        result, the token will be counted as a new client, but will not be
        recounted on subsequent connections.
      </li>
      <li>
        Any <b>local auth mounts</b> created before the upgrade will continue to
        count as a unique client, but new mounts created after the upgrade will
        receive an artificial client ID to avoid duplication in the client count.
      </li>
    </ul>
  </Tab>

  <Tab heading="Upgrading from Vault 1.6">
    As of v1.7, Vault forbids users from creating two aliases from the same authN
    mount under a single entity. Additionally, Vault 1.9 forbids mapping multiple
    service accounts under different namespaces to a single entity.

    Each unique combination of authN mount, namespace, and alias, will be counted
    as a distinct client.
  </Tab>
</Tabs>