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docs(errors): clarify timeout error codes and related options #4856

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docs(errors): explain timeout error codes and fetch configuration
theamodhshetty Mar 3, 2026
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docs(errors): drop unsupported timeout code note
theamodhshetty Mar 6, 2026
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31 changes: 31 additions & 0 deletions docs/docs/api/Errors.md
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Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,37 @@ import { errors } from 'undici'
| `ResponseExceededMaxSizeError` | `UND_ERR_RES_EXCEEDED_MAX_SIZE` | response body exceed the max size allowed |
| `SecureProxyConnectionError` | `UND_ERR_PRX_TLS` | tls connection to a proxy failed |

## Timeout-related errors

The timeout errors below are controlled by dispatcher/client options:

| Error code | When it is thrown | Related option |
| ---------- | ----------------- | -------------- |
| `UND_ERR_CONNECT_TIMEOUT` | A connection could not be established before the connection timeout elapsed. | [`connect.timeout`](/docs/docs/api/Client.md#parameter-connectoptions) |
| `UND_ERR_HEADERS_TIMEOUT` | The full response headers were not received before the headers timeout elapsed. | [`headersTimeout`](/docs/docs/api/Client.md#parameter-clientoptions) |
| `UND_ERR_BODY_TIMEOUT` | While reading the response body, no new data arrived before the body timeout elapsed. | [`bodyTimeout`](/docs/docs/api/Client.md#parameter-clientoptions) |
| `UND_ERR_SOCKET` | A generic socket-level failure happened (including some timeout-related socket errors). | Inspect `error.socket` and adjust your dispatcher/client socket settings. |

### Configuring timeouts for `fetch`

If you are using `fetch` (including Node.js built-in `fetch`), configure timeouts
through the global dispatcher:

```js
import { Agent, setGlobalDispatcher, fetch } from 'undici'

setGlobalDispatcher(new Agent({
connect: { timeout: 10_000 }, // connection phase
headersTimeout: 15_000, // wait for response headers
bodyTimeout: 30_000 // wait between response body chunks
}))

await fetch('https://example.com/data')
```

You can inspect timeout error codes from `error.code` or (for wrapped fetch
errors) from `error.cause?.code`.

Be aware of the possible difference between the global dispatcher version and the actual undici version you might be using. We recommend to avoid the check `instanceof errors.UndiciError` and seek for the `error.code === '<error_code>'` instead to avoid inconsistencies.
### `SocketError`

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