---
title: Configuration
description: Every environment variable, binding, and endpoint of the server, with its default and the platforms it applies to.
sidebar:
    label: Configuration reference
---

The server reads its configuration from the Worker's environment on Cloudflare and from `process.env` on every other platform. It checks the values on each request. An invalid value fails the request with a `500` error, and the server logs `Invalid server configuration:` followed by the reason.

## Server variables

| Variable                         | Required | Default | Description                                                                                                          |
| -------------------------------- | -------- | ------- | -------------------------------------------------------------------------------------------------------------------- |
| `TURBO_TOKEN`                    | Yes      | None    | The bearer token that every client sends. Can't be empty.                                                            |
| `BUCKET_OBJECT_EXPIRATION_HOURS` | No       | `720`   | How long to keep an artifact, in whole hours. At least `1`. Also the KV TTL. See [Retention and expiry](/retention). |

## Cloudflare bindings

Bindings exist only on Cloudflare Workers.

| Binding    | Type         | Description                                                          |
| ---------- | ------------ | -------------------------------------------------------------------- |
| `KV_STORE` | KV namespace | Stores artifacts in [Workers KV](/storage/kv). Wins over `R2_STORE`. |
| `R2_STORE` | R2 bucket    | Stores artifacts in [R2](/storage/r2).                               |

## S3 variables

Setting `S3_BUCKET` turns on [S3-compatible storage](/storage/s3). The server uses it only when no custom adapter and no binding is configured.

| Variable               | Required    | Default                                                   | Description                                                                                    |
| ---------------------- | ----------- | --------------------------------------------------------- | ---------------------------------------------------------------------------------------------- |
| `S3_BUCKET`            | Yes, for S3 | None                                                      | The bucket name. Can't be empty.                                                               |
| `S3_ENDPOINT`          | Yes, for S3 | None                                                      | The S3 API URL, such as `https://s3.us-east-1.amazonaws.com`. The server uses only its origin. |
| `S3_REGION`            | No          | `AWS_REGION`, then `AWS_DEFAULT_REGION`, then `us-east-1` | The signing region. Use `auto` for R2.                                                         |
| `S3_ACCESS_KEY_ID`     | No          | `AWS_ACCESS_KEY_ID`                                       | The access key ID.                                                                             |
| `S3_SECRET_ACCESS_KEY` | No          | `AWS_SECRET_ACCESS_KEY`                                   | The secret access key.                                                                         |
| `S3_SESSION_TOKEN`     | No          | `AWS_SESSION_TOKEN`, when both keys come from `AWS_*`     | A session token for temporary credentials.                                                     |
| `S3_FORCE_PATH_STYLE`  | No          | `false`                                                   | `true` sends requests to `<endpoint>/<bucket>` instead of `<bucket>.<endpoint>`.               |

The `AWS_*` fallbacks come from the process environment. The server reads no AWS profiles or SSO sessions.

## Build and platform variables

| Variable       | Applies to             | Description                                                                                                                 |
| -------------- | ---------------------- | --------------------------------------------------------------------------------------------------------------------------- |
| `NITRO_PRESET` | Build                  | The build target, such as `node_server` or `aws_lambda`. Defaults to `cloudflare_module`. See [Choose a platform](/deploy). |
| `PORT`         | Node.js, Bun, and Deno | The port to listen on. Defaults to `3000`.                                                                                  |
| `HOST`         | Node.js, Bun, and Deno | The address to bind to.                                                                                                     |
| `CRON_SECRET`  | Vercel                 | The secret that Vercel sends with cron requests. See [Vercel](/deploy/vercel).                                              |

A [custom adapter](/storage/custom-adapter) can read any other variable you define.

## Endpoints

| Endpoint                                | Auth         | Description                                                                        |
| --------------------------------------- | ------------ | ---------------------------------------------------------------------------------- |
| `GET /`                                 | None         | Redirects to this documentation.                                                   |
| `GET /ping`                             | None         | Answers `pong`. Use it as a health check.                                          |
| `/v8/artifacts/...`                     | Bearer token | The Remote Cache API. The [API reference](/api) documents every operation.         |
| `POST /internal/delete-expired-objects` | Bearer token | Runs the expiry task. See [Retention and expiry](/retention#run-expiry-on-demand). |

Responses under `/v8` allow requests from any origin, so a browser can call the API. Errors return a JSON body with a `code` and a `message`, such as `{"code":"unauthorized","message":"Missing or invalid bearer token"}`.