Summary: Neon injects branch-scoped variables like DATABASE_URL into deployed functions automatically. Set your own variables with --env at deploy time or in neon.ts, and pull branch variables locally with neon env pull.

Neon-injected variables and how to set your own secrets.

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.

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.

Note: 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). The @neon/ai-sdk-provider handles this routing for you.

Note: 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.)

For type-safe access, the @neon/env package ships parseEnv. It takes your neon.ts config and returns a typed env object validated against the services the config declares:

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.

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

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

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

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:

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:

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.

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:

neon env pull

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

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.

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