---
title: FatalError
description: Throw to mark a step as permanently failed without retrying.
type: reference
summary: Throw FatalError in a step to mark it as permanently failed and prevent retries.
prerequisites:
  - /docs/foundations/errors-and-retries
related:
  - /docs/api-reference/workflow/retryable-error
---

When a `FatalError` is thrown in a step, it indicates that the workflow should not retry a step, marking it as failure.

You should use this when you don't want a specific step to retry.

```typescript lineNumbers
import { FatalError } from "workflow"

async function fallibleWorkflow() {
    "use workflow"
    await fallibleStep();
}

async function fallibleStep() {
    "use step"
    throw new FatalError("Fallible!") // [!code highlight]
}
```

## API signature

### Constructor

`new FatalError(message)`

| Parameter | Type     | Description        |
| --------- | -------- | ------------------ |
| `message` | `string` | The error message. |

### Properties

<TSDoc
definition={`
interface FatalError {
  /** The error message. */
  message: string;
  /** Always true. Marks the error as non-retryable. */
  fatal: boolean;
}
export default FatalError;`}
/>

### Static methods

#### `FatalError.is(value)`

Type-safe check for `FatalError` instances. Preferred over `instanceof` because it works across module boundaries and VM contexts.

```typescript
import { FatalError } from "workflow"
declare const error: unknown; // @setup

if (FatalError.is(error)) {
  // error is typed as FatalError
}
```