---
title: fn::final
url: /docs/esc/concepts/builtin-functions/fn-final/
---
The `fn::final` built-in function marks a value as final, preventing child environments from overriding it. If a child environment attempts to override a final value, the value is not overridden and a validation warning is raised.

## Declaration

```yaml
fn::final: value
```

### Parameters

| Property | Type | Description                          |
|----------|------|--------------------------------------|
| `value`  | any  | The value to mark as final.

### Returns

The original value, marked as final so that it cannot be overridden by child environments.