# Choose SDK or HTTP API [#choose-sdk-or-http-api] Choose the SDK when your application can import TypeScript packages. Choose the HTTP API when the calculation should run on the server or the caller cannot import TypeScript packages. The SDK's root, AU and schema entrypoints also support browser callers; those calculations run on the caller's device. ## Choose by environment [#choose-by-environment] | Environment | Choose | Why | | ------------------------------------------------ | --------------- | --------------------------------------------------------------------------------------------------------------- | | Server-side TypeScript application | Plain SDK | You get typed calculator inputs and reports without HTTP transport. | | TypeScript application that wants typed failures | Safe SDK | You get `TaxKit.safe.calculate` result values. | | Effect application | Effect SDK | You can compose `calculateRunRequest`, `calculateReportRequest` and `calculateReport` with services and layers. | | Browser application | HTTP API or SDK | HTTP sends the request to the server; the browser-safe SDK calculates on the device. | | Non-TypeScript backend | HTTP API | You can use JSON and generated OpenAPI reference. | | Generated endpoint contract | HTTP API | OpenAPI owns endpoint shape and status codes. | ## Recommended paths [#recommended-paths]

On the device

On a server

Where will the caller run?

Server-side TypeScript

Effect application

Browser

Another language

Where should the browser calculation run?

Use the plain SDK

Use the Effect SDK

Use the HTTP API

 The HTTP API calls the calculator service directly. The SDK calls the same service in-process. Keep tax logic in the shared calculator and rule packages. ## Next steps [#next-steps] * Use [Plain SDK](/sdk/plain-sdk) for most server-side TypeScript apps. * Use [Effect SDK](/sdk/effect-sdk) for in-process Effect composition. * Use the API section when you need HTTP endpoint details.