Getting Started

Install the dependencies
- pnpm
- npm
- yarn
- bun
pnpm add @layerfig/config
npm install @layerfig/config
yarn add @layerfig/config
bun add @layerfig/config
Zod v4 ships with the package — you don’t need to install it separately. See Compatibility.
Define your files
- Directoryapp
  - Directoryconfig
    base.json
  - Directorysrc
    …
    Directoryconfig
    index.ts
- index.ts
- base.json
```
import { ConfigBuilder, FileSource } from "@layerfig/config";

export const config = new ConfigBuilder({
  validate: (finalConfig, z) =>
    z.object({
        appURL: z.url(),
        port: z.coerce.number().check(z.int(), z.positive()),
      })
      .parse(finalConfig),
})
  .addSource(new FileSource("base.json"))
  .build();
```
```
{
  "appURL": "http://localhost:3000",
  "port": 3000
}
```

Use your type-safe config

Now, you can access the configuration anywhere in your server-side code:

import { config } from "./config";

config.appURL; // string => "http://localhost:3000"
config.port; // number => 3000

Next steps

That is a single layer. The point of Layerfig is stacking several:

Add a per-environment file on top of base.json.
Override values at runtime with environment variables.
Reference environment variables from inside your config files with slots.

Compatibility

Requirement	Detail
Zod	v4 — bundled, and re-exported as `z`
Parser packages	`@layerfig/parser-*` v6 pairs with `@layerfig/config` v3
Module formats	ESM and CommonJS on the server; ESM only for `/client`
Runtime	Any runtime with `node:fs` and `node:path` — see Deno