# Neon Functions environment variables

## Neon-injected variables

Neon injects connection strings, credentials, and service URLs automatically at runtime. You don't declare these in `neon.ts` or pass them at deploy time. They're resolved from the branch the function is deployed to. This is why a function doesn't configure Postgres, the AI Gateway, or Object Storage itself: enable the service, and its credentials are there in `process.env`.

Each variable is present only when its service is enabled on the branch. `DATABASE_URL` and `DATABASE_URL_UNPOOLED`, for example, are undefined on a functions-only branch with no Postgres database.

| Variable                                     | Service             | Description                                                                                                              |
| -------------------------------------------- | ------------------- | ------------------------------------------------------------------------------------------------------------------------ |
| `DATABASE_URL`                               | Postgres            | Pooled connection string. Use this for most queries.                                                                     |
| `DATABASE_URL_UNPOOLED`                      | Postgres            | Direct connection string. Use for migrations, `LISTEN`/`NOTIFY`, and multi-round-trip transactions.                      |
| `NEON_BRANCH`                                | Core                | Branch name (e.g. `main`, `preview/foo`). Present on all branches.                                                       |
| `NEON_AUTH_BASE_URL`                         | Managed Better Auth | Base URL for Managed Better Auth.                                                                                        |
| `NEON_AUTH_JWKS_URL`                         | Managed Better Auth | JWKS endpoint for verifying Managed Better Auth JWTs. See [Authentication](/guides/neon-functions-authentication).       |
| `NEON_DATA_API_URL`                          | Data API            | Base URL for the Neon Data API (PostgREST). Present when the Data API is provisioned on the branch.                      |
| `NEON_AI_GATEWAY_TOKEN`                      | AI Gateway          | Gateway bearer token.                                                                                                    |
| `NEON_AI_GATEWAY_BASE_URL`                   | AI Gateway          | Gateway host root. Append a dialect route, e.g. `/v1` for Chat Completions or `/openai/v1` for the OpenAI Responses API. |
| `AWS_ACCESS_KEY_ID`, `AWS_SECRET_ACCESS_KEY` | Object Storage      | S3-compatible credentials for the branch's buckets.                                                                      |
| `AWS_ENDPOINT_URL_S3`, `AWS_REGION`          | Object Storage      | S3 endpoint and region. The `AWS_*` names mean the AWS SDKs work with no setup.                                          |

These variables are branch-scoped: each branch injects its own values. A function deployed to a preview branch connects to that branch's database, not the default branch's.

:::callout{intent="note" title="Two AI Gateway endpoints"}
`NEON_AI_GATEWAY_BASE_URL` is the bare gateway host: append a dialect path yourself. Use `/openai/v1` for the OpenAI **Responses API** and `/v1` for **Chat Completions** (see [Chat completions](/guides/ai-gateway-chat-completions)). The [`@neon/ai-sdk-provider`](/guides/neon-functions-agents) handles this routing for you.
:::

:::callout{intent="note" title="Local pull vs. deployed runtime"}
A deployed function gets credentials injected automatically for every service enabled on its branch, so you don't ship a `.env`. For local development, `neon env pull` writes the branch's core variables plus credentials for any services you **declare in `neon.ts`**, which can be a subset. Declare a service (`auth: true`, `dataApi: true`, `aiGateway: true`, `buckets: { ... }`) to pull its credentials locally and to get type-safe access. (Outside a `neon.ts` workflow, `neon env pull` still writes the branch's core variables — see the [`env` command](/guides/apis-sdks-cli-env).)
:::

For type-safe access, the [`@neon/env`](https://www.npmjs.com/package/@neon/env) package ships `parseEnv`. It takes your `neon.ts` config and returns a typed env object validated against the services the config declares:

```typescript
import { parseEnv } from '@neon/env';
import config from './neon';

const env = parseEnv(config);
env.postgres.databaseUrl;          // DATABASE_URL
env.postgres.databaseUrlUnpooled;  // DATABASE_URL_UNPOOLED
env.auth.baseUrl;                  // NEON_AUTH_BASE_URL (only when auth: true)
env.auth.jwksUrl;                  // NEON_AUTH_JWKS_URL (only when auth: true)
```

TypeScript narrows the shape based on your config: `env.auth` is only present when `auth: true` is set in `neon.ts`.

## User-defined variables

Each deployment carries its own snapshot of user-defined variables. To change one, deploy again.

### At deploy time

Pass `--env KEY=VALUE` to `neon functions deploy`. The flag is repeatable:

```bash
neon functions deploy hello --src functions/hello.ts --env RESEND_API_KEY=re_...
```

Neon injects variables like `DATABASE_URL`, `NEON_AI_GATEWAY_*`, `AWS_ACCESS_KEY_ID`, `AWS_SECRET_ACCESS_KEY`, `AWS_ENDPOINT_URL_S3`, and `AWS_REGION` when the matching service is enabled on the branch. These are defaults, not reserved names: if you define a variable with the same name, your value overrides the injected one.

A deploy doesn't wipe variables set by earlier deploys. The `--env` flags you pass are merged into the existing set:

- `--env KEY=value` adds or updates `KEY`
- `--env KEY=` (empty value) deletes `KEY`
- Variables you don't mention carry over unchanged

### In neon.ts

Declare variables under the function's `env` field. Values are resolved when `neon deploy` runs, so you can read from `process.env` to avoid hardcoding secrets:

```typescript title="neon.ts"
import { defineConfig } from "@neon/config/v1";

export default defineConfig({
  functions: {
    hello: {
      name: "My first function",
      source: "./functions/hello.ts",
      env: {
        RESEND_API_KEY: process.env.RESEND_API_KEY!,
      },
    },
  },
});
```

Load a `.env` file before running `neon deploy` to make secrets available during config evaluation:

```bash
neon deploy --env .env.production
```

The file isn't forwarded to the function directly. Only variables declared in the `env` field are deployed; `--env` only controls what `process.env` contains when `neon.ts` is evaluated.

## Pull variables locally

`neon link` and `neon checkout` pull the branch's Neon-injected variables into a local `.env` file automatically (pass `--no-env-pull` to skip). To re-pull at any time:

```bash
neon env pull
```

By default this writes to `.env` if it exists, otherwise `.env.local`. Use `--file` to write to any file:

```bash
neon env pull --file .env.preview
```

To pull from a different branch, switch with `neon checkout`; it pulls the new branch's variables as part of the switch.

`env pull` writes only the Neon-managed variables and preserves every other line in the file. That's the core variables `DATABASE_URL`, `DATABASE_URL_UNPOOLED`, and `NEON_BRANCH`, plus the variables for any service you **declare in `neon.ts`**: the Managed Better Auth URLs, the Neon Data API URL, the AI Gateway credentials (`NEON_AI_GATEWAY_TOKEN`, `NEON_AI_GATEWAY_BASE_URL`), and the Object Storage credentials (`AWS_*`). It also writes a public invocation URL for each Neon Function as `NEON_FUNCTION_<SLUG>_BASE_URL` (origin only, matching `NEON_AUTH_BASE_URL` and `NEON_AI_GATEWAY_BASE_URL`), so code running locally can call your deployed functions by reading their URLs from the environment. These variables are local-only: they aren't injected into a deployed function's runtime. To call one function from another at runtime, pass the target URL explicitly (for example as a `--env` variable) or read the incoming request's `Host` header.

## Constraints

| Constraint                   | Value  |
| ---------------------------- | ------ |
| Max variables per deployment | 1,000  |
| Max total size               | 64 KiB |

## Need help?

Join our [Discord Server](https://neon.com/discord) to ask questions or see what others are doing with Neon. For paid plan support options, see [Support](/guides/postgres-introduction-support).

## Related pages

- [AI tools for Agents](./ai-agents-on-neon-index.md)
- [APIs & SDKs](./apis-sdks-index.md)
- [Changelog](../changelog.md)
- [Integrating with Neon](./building-on-neon-index.md)
- [Lakebase Postgres](./postgres-index.md)
- [Managed Better Auth](./auth-index.md)
- [More](./more-index.md)
- [Neon AI Gateway](./ai-gateway-index.md)
- [Neon community](./community-index.md)
- [Neon documentation](./neon-docs-index.md)

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