Validators

ArkType, Zod, and Valibot can all describe an environment variable. ArkEnv ships two engines that share arkenv(), fail-fast errors, and the framework plugins. You pick the one that matches the schemas you already write.

Shared options (env, coerce, and the rest) apply to both. toJsonSchema is on @arkenv/standard only. ArkType already exposes JSON Schema. The engines differ in schema style and peer dependencies.

Pick the engine that matches the schema library you write, then follow the cookbook below.

Side by side

The same keys, three declaration styles. Zod 4.2+ does not need z.coerce, and Valibot does not need v.transform(Number); ArkEnv coerces first.

import arkenv from "@arkenv/core";

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

Install either stack the same way you would any env schema: one validation package, then framework plugins if you need them.

ArkType engine:

npm install @arkenv/core arktype

Standard Schema engine (Zod):

npm install @arkenv/standard zod

Standard Schema engine (Valibot):

npm install @arkenv/standard valibot @valibot/to-json-schema

When each fits

ArkType itself implements Standard Schema. If you already depend on ArkType, stay on @arkenv/core rather than wrapping ArkType types through @arkenv/standard.

Packaging

Engines are separate packages so peer dependencies stay honest. Framework plugins stay single packages with /standard subpaths (@arkenv/nextjs/standard, @arkenv/vite-plugin/standard, and so on) instead of a second npm package per host.

JSON Schema and coercion

Standard Schema and Standard JSON Schema are orthogonal specs: one is about validation, the other about converting a type to JSON Schema. A value can implement one, both, or neither.

ArkEnv's pre-coercion step for @arkenv/standard prefers Standard JSON Schema v1 on the value (~standard.jsonSchema.input / .output). When a library keeps conversion outside the schema, use a first-class subpath or the optional toJsonSchema escape hatch.

See Coercion and parsing.

A one-file Env.assert(process.env) works for a hello-world Node script. ArkEnv adds env-specific errors, automatic coercion, a CLI, and framework plugins that keep server secrets out of the client graph. See Why ArkEnv? for DIY, Varlock, T3 Env, znv, Envalid, and related tools.

Cookbooks