@g14o/env-core

@g14o/env-core

Framework-agnostic, typesafe environment variables validated with any Standard Schema library (Zod, Valibot, ArkType, and others).

Zero runtime dependencies — install only the validator you use.

Install

pnpm add @g14o/env-core zod

Peer dependencies

zod, valibot, and arktype are optional peers — install the validator you use. Ranges follow Standard Schema v1 support on each major line (arktype ^2.0.0, valibot ^1.0.0, zod ^4.0.0). typescript (>=5) is optional but recommended for typed env definitions.

Usage

import { createEnv } from "@g14o/env-core";
import * as z from "zod";

export const env = createEnv({
  clientPrefix: "PUBLIC_",
  server: {
    DATABASE_URL: z.url(),
    OPEN_AI_API_KEY: z.string().min(1),
  },
  client: {
    PUBLIC_API_URL: z.url(),
  },
  runtimeEnv: process.env,
  emptyStringAsUndefined: true,
});

On the server, all variables are validated and readable. On the client, only client keys are validated; accessing a server key throws with the exact variable name.

Import the same env object in server and client code — no separate client export is required.

How client protection works

createEnv returns a Proxy around the validated environment object (on both server and client):

• Server: the proxy is transparent — all validated server and client keys are readable.
• Client: only client schemas are validated at import time (missing server vars in process.env do not throw).
• Client access: any property that is not a declared client key throws with the exact name, e.g. DATABASE_URL or typos like NOT_DECLARED.
• Interop: __esModule and $typeof are ignored so bundlers and React do not trigger false positives.

Valibot

import { createEnv } from "@g14o/env-core";
import * as v from "valibot";

export const env = createEnv({
  clientPrefix: "PUBLIC_",
  server: {
    DATABASE_URL: v.pipe(v.string(), v.url()),
  },
  client: {
    PUBLIC_API_URL: v.pipe(v.string(), v.url()),
  },
  runtimeEnv: process.env,
});

ArkType

import { createEnv } from "@g14o/env-core";
import { type } from "arktype";

export const env = createEnv({
  server: {
    DATABASE_URL: type("string.url"),
  },
  clientPrefix: "PUBLIC_",
  client: {
    PUBLIC_API_URL: type("string.url"),
  },
  runtimeEnv: process.env,
});

Strict runtime mapping (bundler-friendly)

When your framework only inlines env vars you reference explicitly, use runtimeEnvStrict:

import { createEnv } from "@g14o/env-core";
import * as z from "zod";

export const env = createEnv({
  server: { DATABASE_URL: z.url() },
  clientPrefix: "NEXT_PUBLIC_",
  client: { NEXT_PUBLIC_API_URL: z.url() },
  runtimeEnvStrict: {
    DATABASE_URL: process.env.DATABASE_URL,
    NEXT_PUBLIC_API_URL: process.env.NEXT_PUBLIC_API_URL,
  },
});

Overriding default error handler

import { createEnv } from "@g14o/env-core";

export const env = createEnv({
  // ...
  // Called when schema validation fails.
  onValidationError: (issues) => {
    console.error("Invalid environment variables:", issues);
    throw new Error("Invalid environment variables");
  },
  // Called when a server variable is accessed on the client.
  onInvalidAccess: (variable) => {
    console.error("Invalid access to server variable:", variable);
    throw new Error("Invalid access to server variable");
  },
});

Tell when we're in a server context

import { createEnv } from "@g14o/env-core";

export const env = createEnv({
  // ...
  // Tell when we're in a server context
  isServer: typeof window === "undefined", // or straight up `true` or `false`
});

Skip validation

skipValidation bypasses both schema validation and the client-access proxy. Only use it when exposing the picked keys acceptable for the current runtime.

import { createEnv } from "@g14o/env-core";

export const env = createEnv({
  // ...
  // Tell the library to skip validation and return picked runtime values only
  skipValidation: true,
});

Options

Option	Description
server	Server-only variables (validated on server; throw on client access)
client	Client-safe variables (validated on server and client)
clientPrefix	Optional prefix required on all client keys (type + runtime)
runtimeEnv	Record to read values from (e.g. process.env)
runtimeEnvStrict	Explicit per-key mapping; mutually exclusive with runtimeEnv
emptyStringAsUndefined	Treat "" as undefined before validation
isServer	Override server detection (default: typeof window === "undefined")
onValidationError	Hook when schema validation fails; may throw custom error, otherwise default InvalidEnvironmentVariablesError is thrown
onInvalidAccess	Hook when a server key is accessed on the client; may throw custom error, otherwise default server-access error is thrown
skipValidation	Bypasses both schema validation and the client-access proxy. Only use it when exposing the picked keys acceptable for the current runtime (default: false)

Security

Server values are never validated or exposed on the client. Importing a single env.ts that defines server schemas still ships those names to the client bundle. For sensitive names, split into env/server.ts and env/client.ts.

License

MIT