schema

arkenv() accepts a schema that maps environment variable names to validators. Core uses the ArkType DSL (and compiled type() values). Standard mode accepts a map of Standard Schema validators.

Declarative map

Pass a map of ArkType strings (or nested objects). This is an EnvSchema: each value is validated against ArkEnv's ArkType scope before parsing.

import arkenv from "@arkenv/core";

export const env = arkenv({
  NODE_ENV: "'development' | 'production' | 'test' = 'development'",
  HOST: "string.host = 'localhost'",
  PORT: "number.port = 3000",
  DATABASE_URL: "string",
});

Compiled type()

Build the schema once with type() when you reuse it across runtimes or packages.

import arkenv, { type } from "@arkenv/core";

export const Env = type({
  PORT: "number.port = 3000",
  DATABASE_URL: "string",
});

export const env = arkenv(Env);

See Reusing schemas.

Standard Schema maps

With @arkenv/standard, every value must be a Standard Schema validator (Zod, Valibot, and others). ArkType DSL strings fail.

import arkenv from "@arkenv/standard";
import * as z from "zod";

export const env = arkenv({
  PORT: z.int().min(0).max(65535),
  DATABASE_URL: z.url(),
});

Inferring types

Infer<T> works for declarative maps, compiled ArkType types, and Standard Schema values.

import arkenv, { type Infer } from "@arkenv/core";

const schema = {
  DATABASE_URL: "string",
  PORT: "number.port = 3000",
} as const;

export const env = arkenv(schema);
export type Env = Infer<typeof schema>;

Client and server schemas

Framework packages enforce public prefixes on a flat schema:

• Flat: one schema; public prefixes decide client exposure
• Optional recipe: two modules with extends when names must stay off the client type graph

Details: Client vs. server, @arkenv/nextjs, @arkenv/nuxt.

Next steps