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

# Machine Placement and Regional Capacity

<Info>
  **When you scale an app on Fly.io, where your machines land depends on regional capacity. Here's how to keep that from surprising you.**
</Info>

Let’s say you run `fly scale count` and tell it to drop 10 machines into `dfw` and 10 more into `iad`. If either of those regions is out of capacity, *the entire scale operation fails*. Nothing gets placed. It’s all or nothing.

Most of the time this just works—`dfw` and `iad` are solid bets for region choices. But some regions, like `sjc`, `gru`, and `bom`, tend to be in high demand. If you hardcode your placement into one of those and cross your fingers, you might find yourself scaling to zero.

### Where can you deploy?

Run `fly platform regions` to see the regions where Fly.io has datacenters, along with their region codes. Use those codes to set region preferences for your Machines.

### Let the scheduler help

For individual machine operations like `fly machine clone` or creating a new machine, you can give the scheduler some leeway. Instead of pinning a single region, you hand it a prioritized list or a geographic group. It tries each in order until it finds one that works.

For example:

```
fly machine clone -r "iad,dfw"
```

That says: try `iad`, then fall back to `dfw`.

### Geographic groups and aliases

You can use geographic aliases like `us`, `eu`, or `sa` to fan out across a broader area.

| Alias       | Area          |
| ----------- | ------------- |
| `apac`      | Asia-Pacific  |
| `eu`        | Europe        |
| `na`        | North America |
| `sa`        | South America |
| `us`, `usa` | United States |

### Examples:

* Try London first, then fall back to anywhere in Europe:

```
lhr,eu
```

* Try any US region first, then Europe:

```
us,eu
```

* Try any North American region first, then any South American region:

```
na,sa
```

<h3 id="scale-commands-dont-yet-do-this">
  Scale commands don't (yet) do this
</h3>

Right now, flexible placement doesn’t apply to `scale`, `deploy`, or `launch`. If you want to scale across regions with fallbacks, the supported way to do that is by cloning machines individually (or using `fly machine create`), with region preferences.

(We know that’s a bit clunky. We’re working on it.)

### Machines API support

If you're driving placement from the Machines API (`api.machines.dev`), all of this flexibility is available there: prioritized region lists, meta-regions, and `any` placement.

### A word on architecture

This only helps if your app actually works when deployed across multiple regions. That means not assuming low-latency connections between machines, and avoiding coordination patterns that only work in single-region setups.

<Info>
  Want to see where your app might run?
  Here's the [current list](/reference/regions): ams, arn, bom, cdg, dfw, ewr, fra, gru, iad, jnb, lax, lhr, nrt, ord, sin, sjc, syd, yyz.
</Info>

### Related reading

* [An Introduction to Fly Machines](/machines/overview)
* [Regions Reference](/reference/regions)
* [Fly Machines API](/machines/api)
* [Get Regions](/api/machines/platform/get-regions)