---
title: "Tasks"
description: "Tasks are individual building blocks of a Run."
---

> A Task is a resumable unit of a Run that can be retried, resumed and is logged.

## Tasks vs regular code

In the `run()` function you can use regular code and you can use Tasks.

```ts
client.defineJob({
  id: "new-user",
  name: "Run when a new user signs up",
  version: "0.0.1",
  trigger: eventTrigger({
    name: "new.user",
    schema: z.object({
      userId: z.string(),
    }),
  }),
  integrations: {
    resend,
  },
  run: async (payload, io, ctx) => {
    // regular code, not a Task
    // the inputs/outputs of this function are not sent to the Trigger.dev platform
    const user = await prisma.user.findUnique({
      where: { id: payload.userId },
      select: { email: true, name: true },
    });
    if (!user) throw new Error(`User not found: ${payload.userId}`);

    // Integration functions are Tasks
    await io.resend.sendEmail("Welcome email", {
      to: user.email,
      from: "jane@acme.inc",
      subject: "Welcome!",
      html: welcomeEmail(user.name),
    });

    // built-in io functions are Tasks
    await io.wait("wait", 60 * 60 * 3); // wait for 3 hours

    // You can wrap your own code in a Task, for retrying, resumability and logging
    const response = await io.runTask("my-task", { name: "My Task" }, async () => {
      return await longRunningCode(payload.userId);
    });

    return response;
  },
});
```

## The benefits of Tasks

Tasks are a powerful concept that gives you a lot of benefits:

- **Resumability** – Runs can exceed the maximum timeout on serverless platforms. If a Run exceeds this limit, it will be re-run. When it is re-run, any completed Tasks return their original output and they aren't re-run. Read more about [Resumability](/documentation/concepts/resumability).
- **Retryable** – If a Task fails, it will be retried. You can configure how (or if) a Task is retried. Full details in the [io SDK reference](/sdk/io).
- **Logging** – Tasks are logged, so you can see what happened in a Run. Find out more about [viewing runs](/documentation/guides/viewing-runs).

## Subtasks

A Task can have multiple subtasks, and so on. This is useful for breaking down a large Task into smaller Tasks. We currently support nesting 5 levels deep.

## Task Keys

The first param of all Tasks is a `key`. This is a unique identifier for the Task inside that Run. It is used for resumability and logging. It is also used to identify the Task in the [Viewing Runs Dashboard](/documentation/guides/viewing-runs).

## References

<CardGroup cols={2}>
  <Card title="Resumability" icon="clock" href="/documentation/concepts/resumability">
    Runs can be very long-running. Learn how we handle this.
  </Card>
  <Card title="Integrations" icon="grid-2" href="/documentation/concepts/integrations">
    Integrations utilize Tasks.
  </Card>
  <Card title="`io` SDK Reference" icon="wrench" href="/sdk/io">
    The `io` object allows you to easily run a Task yourself.
  </Card>
  <Card title="Viewing Runs Dashboard" icon="globe" href="/documentation/guides/viewing-runs">
    View all Runs for a Job, all the way down to individual Tasks.
  </Card>
</CardGroup>
