```js
// @noErrors
import { defineEnvVars } from '@sveltejs/kit/env';
```

## defineEnvVars

Utility for defining [environment variables](/docs/kit/environment-variables),
which are made available via `$app/env/public` and `$app/env/private`.

```js
// @errors: 7031
import { defineEnvVars } from '@sveltejs/kit/env';
import * as v from 'valibot';

export const variables = defineEnvVars({
	API_URL: {
		schema: v.pipe(v.string(), v.url())
	},
	PORT: {
		schema: (value) => {
			if (value === undefined) return 3000;
			const port = Number(value);
			if (!Number.isInteger(port)) throw new Error('PORT must be an integer');
			return port;
		}
	}
});
```

<div class="ts-block">

```dts
function defineEnvVars<
	T extends Record<string, EnvVarConfig<any>>
>(variables: T): DefinedEnvVars<T>;
```

</div>



## DefinedEnvVars

The return type of [`defineEnvVars`](/docs/kit/@sveltejs-kit-env#defineEnvVars).

<div class="ts-block">

```dts
type DefinedEnvVars<
	T extends Record<string, EnvVarConfig<any>>
> = {
	readonly [K in keyof T]: EnvVarEntry<T[K]>;
};
```

</div>

## EnvVarConfig

[Environment variables](/docs/kit/environment-variables) can be configured by exporting
a `variables` object from `src/env.ts`, using [`defineEnvVars`](/docs/kit/@sveltejs-kit-env#defineEnvVars).

<div class="ts-block">

```dts
interface EnvVarConfig<T> {/*…*/}
```

<div class="ts-block-property">

```dts
public?: boolean;
```

<div class="ts-block-property-details">

<div class="ts-block-property-bullets">

- <span class="tag">default</span> `false`

</div>

Whether the environment variable can be accessed by client-side code.
- if `true`, it can be imported from `$app/env/public`
- if `false`, it can be imported from `$app/env/private`, which is a [server-only module](/docs/kit/server-only-modules)

</div>
</div>

<div class="ts-block-property">

```dts
static?: boolean;
```

<div class="ts-block-property-details">

<div class="ts-block-property-bullets">

- <span class="tag">default</span> `false`

</div>

Whether the value is determined at build time or when the app runs.
- if `true`, the build time value is inlined into the bundle. This enables optimisations like dead-code elimination
- if `false`, the value is read from the environment when the app starts

</div>
</div>

<div class="ts-block-property">

```dts
schema?: StandardSchemaV1<string | undefined, T> | ((value: string | undefined) => T | undefined);
```

<div class="ts-block-property-details">

A [Standard Schema](https://standardschema.dev/) validator that is applied to the value when the app starts.
Alternatively, a function that returns the (possibly transformed) value, or throws an error explaining
the problem. Returning `undefined` is valid, so a function can describe an optional variable.
The validator can output any value — not necessarily a string — but public, non-static values must be
serializable by [devalue](https://github.com/sveltejs/devalue) so that they can be sent to the browser.

If omitted, the value must be set, but may be an empty string.

</div>
</div>

<div class="ts-block-property">

```dts
description?: string;
```

<div class="ts-block-property-details">

A description of the variable that will be used for inline documentation on hover.

</div>
</div></div>