# Relay locations and regions

> Explore the available Relay regions, and learn how to select the best one for your players.

As a developer using Relay, you can allow players to select a [Relay server](./relay-servers.md) from a list of available regions.

By selecting the closest Relay server, the player can minimize the potential latency and guarantee the smoothest possible experience for their session.

The following table has the Relay regions available across the globe:

## Americas, Europe

| Identifier           | Location       |
| -------------------- | -------------- |
| `us-east1`           | South Carolina |
| `us-central1`        | Iowa           |
| `us-west1`           | Oregon         |
| `southamerica-east1` | Sao Paulo      |
| `europe-north1`      | Finland        |
| `europe-central2`    | Poland         |
| `europe-west4`       | Netherlands    |

## Asia, Australia

| Identifier             | Location  |
| ---------------------- | --------- |
| `asia-southeast1`      | Singapore |
| `asia-northeast1`      | Tokyo     |
| `asia-south1`          | Mumbai    |
| `australia-southeast1` | Sydney    |

## How region selection works

Typically, you don't need to specify a region in an allocation request:

* The [Multiplayer Services SDK](/mps-sdk.md) defaults to using [Quality of Service (QoS)](./qos.md) measurements to select a region.
  * You can use `WithRelayNetwork` with [`RelayNetworkOptions`](https://docs.unity3d.com/Packages/com.unity.services.multiplayer@latest?subfolder=/api/Unity.Services.Multiplayer.RelayNetworkOptions.html) to configure a region by name.
* If you omit the region from the `POST /v1/allocate` HTTP request, the service uses the origin network address as a heuristic to pick a region.
* If none of the previous are possible, the service defaults to `us-central1`.

Passing an explicit region identifier overrides this behavior. It's recommended you programmatically check this value against the region listing response and not hardcode any values.

## Fallback for retired regions

Retired regions are not visible in the regions listing endpoint.
Explicit requests to retired regions are automatically redirected to a replacement region; refer to the previous tables for mappings.