# Introduction

Overview of Workers IO and how to get access.

Workers IO helps teams ship reliable software faster. You define the behavior your users depend on, then run it across many realistic scenarios before release, without manually thinking through every path, timing edge, retry, or service failure yourself.

## Things we can help test

- Product workflows that users depend on.
- Retry and timeout behavior.
- Network delays, loss, and blocked dependency paths.
- External service failures and unusual responses.
- Race conditions and ordering bugs.
- Long-running workflows that depend on timers, polling, leases, or scheduled work.

## What is required from you

Most teams start with three files:

- A workload that describes the user behavior or system workflow you care about.
- Fault models under `.workers/fault/` for conditions the workflow should survive.
- Mock file at `.workers/external-mocks.json`, if the workflow depends on outside services.

You can run the same workload from the web UI or from the `wio` CLI.

## Install the CLI

```bash
npm install -g @workersio/cli
wio auth login
```

Then list your connected projects:

```bash
wio projects ls
```

## Next

Read the [Quickstart](/docs/quickstart/) to run your first simulation.