---
title: Request ID
description: Generate or honor unique request identifiers across requests and responses
---

Logixlysia can automatically generate or retrieve unique request identifiers (Request IDs) and attach them to the request context, response headers, and log outputs.

## Basic Usage

You can enable the request ID feature using the `requestId` config option. When set to `true`, it uses the default configuration (`X-Request-Id` header and UUID v4 generator).

```ts
import { Elysia } from 'elysia'
import logixlysia from 'logixlysia'

const app = new Elysia()
  .use(
    logixlysia({
      config: {
        requestId: true
      }
    })
  )
```

## Production Preset

The `prod` preset enables `requestId` automatically by default:

```ts
const app = new Elysia()
  .use(
    logixlysia({
      preset: 'prod' // requestId is enabled automatically
    })
  )
```

## Custom Configuration

For advanced use cases, you can pass a configuration object instead of a boolean:

```ts
const app = new Elysia()
  .use(
    logixlysia({
      config: {
        requestId: {
          // Custom header name to read from / write to
          header: 'X-Correlation-Id',
          // Custom request ID generator function
          generator: () => `req-${crypto.randomUUID()}`
        }
      }
    })
  )
```

### Options

| Option | Type | Default | Description |
|---|---|---|---|
| `enabled` | `boolean` | `true` | Turn request ID generation on or off when using object configuration. |
| `header` | `string` | `'X-Request-Id'` | The header key to check on incoming requests (honoring upstream proxies) and to set on responses. |
| `generator` | `() => string` | `crypto.randomUUID` | A function that returns a unique string to use as the request ID. |

## Log Formatting

When Request ID is enabled, you can output it in your custom log format using the `{requestId}` token:

```ts
const app = new Elysia()
  .use(
    logixlysia({
      config: {
        requestId: true,
        customLogFormat: '{method} {pathname} - Request ID: {requestId}'
      }
    })
  )
```

If Request ID is disabled or not present, the token will render as an empty string.

## Error Responses

If a request fails (e.g. throws an exception), the request ID is still propagated in the response headers (like `X-Request-Id`) and is correctly logged in the HTTP error telemetry context, allowing trace correlation for failed requests.