# Usage limits

A usage limit watches one resource a computer uses over a rolling window. When the computer reaches the limit's threshold, the limit notifies you or pauses the computer.

## Set a limit

Each limit has four parts:

| Part      | What it is                                                         |
| --------- | ------------------------------------------------------------------ |
| Metric    | What is measured, from the list below.                             |
| Window    | The rolling period usage is added up over, from an hour to a year. |
| Threshold | The amount of the metric, in that window, that triggers the limit. |
| Action    | What happens when the computer reaches it.                         |

| Metric             | What it counts                                   |
| ------------------ | ------------------------------------------------ |
| Active CPU         | CPU time the computer's code executes            |
| Provisioned CPU    | vCPUs the computer holds, over time              |
| Active memory      | Memory the computer holds while awake, over time |
| Provisioned memory | Memory the computer is given, over time          |
| Disk               | Storage the computer holds, over time            |
| Egress             | Data the computer sends out                      |
| Exports            | Data exported from the computer's filesystem     |

| Action  | What it does                                                                               |
| ------- | ------------------------------------------------------------------------------------------ |
| Notify  | Sends you a notification, once per window.                                                 |
| Suspend | Pauses the computer until its usage falls back under the threshold as the window rolls on. |

A computer can have up to five limits, each a different metric and window: for example, a notification when it sends 10 GiB in a day and a pause when it uses 100 hours of active CPU in a week.

## When limits are checked

Usage is checked periodically, not as it happens, so a computer can pass its threshold before the check that acts on it. Treat a limit as a safeguard rather than an exact cap.

Limits count resources, not money. To see what a computer costs, see [Pricing](https://elios.ai/pricing).

## Next steps

* [Computers](/computer/concepts/computers): what a computer pays for while it works, idles and freezes
* [Networking](/computer/concepts/networking): choose where computers can connect