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# TypeScript serde layer

> Learn how to enable the TypeScript serde layer in Fern SDK generator to transform API field names to camelCase and validate requests at runtime.

Fern's TypeScript SDK generator includes an optional serde layer that determines whether the generated SDK matches your original API naming conventions (snake\_case vs. camelCase, case-sensitive fields) or follows TypeScript conventions. This serde layer is controlled by the `noSerdeLayer` option.

By default, the serde layer is **disabled** (`noSerdeLayer: true`), meaning field names are preserved exactly as they appear in your API specification.

## When to enable the serde layer

**`generators.yml`**

```yaml title="generators.yml" {7}
groups:
  ts-sdk:
    generators:
    - name: fern-typescript-sdk
      version: 3.95.1
      config:
        noSerdeLayer: false # Enable serde layer
```

When you turn on the serde layer, (`noSerdeLayer: false`), the TypeScript SDK generator includes custom serialization code that:

* Transforms all property names from your API to camelCase
* Validates requests and responses at runtime
* Supports complex types like `Date` and `Set`.

Enable the serde layer when you want idiomatic TypeScript conventions and don't have case-sensitive field conflicts. Keep it disabled when your API has fields that differ only by casing or when you need exact field name preservation.

## Additional configuration options

Several configuration options work alongside an enabled serde layer:

* `skipResponseValidation` disables the serde layer's runtime validation while keeping its transformation features
* `allowExtraFields` permits properties not defined in your schema.
* `useBigInt` enables custom JSON handling to preserve large number precision.

These options only take effect when the serde layer is enabled (`noSerdeLayer: false`), as they require the custom serialization infrastructure.

**`generators.yml`**

```yaml title="generators.yml" {7-10}
groups:
  ts-sdk:
    generators:
    - name: fern-typescript-sdk
      version: 3.95.1
      config:
        noSerdeLayer: false           # Enable serde layer
        skipResponseValidation: true  # Disable runtime validation errors
        allowExtraFields: true        # Allow undefined fields in responses
        useBigInt: true               # Preserve precision for large numbers
```

For the complete list of all TypeScript configuration options, go to [TypeScript configuration](/learn/sdks/generators/typescript/configuration).

> Learn how to enable the TypeScript serde layer in Fern SDK generator to transform API field names to camelCase and validate requests at runtime.