This guide explains the differences between LaunchDarkly’s SDKs and LaunchDarkly’s REST API and associated client libraries, and when you should use each.
LaunchDarkly uses different credentials for integrating your application (SDK credentials) and for managing your account and resources programmatically (REST API access tokens).
Use an SDK credential (SDK key, mobile key, or client-side ID) when you initialize a LaunchDarkly SDK in your application to evaluate feature flags and send analytics. Use an API access token when you call the LaunchDarkly REST API (for example, to create or update flags, manage members, or build integrations).
SDK credentials and API access tokens are separate and are not interchangeable. You cannot use an SDK credentials to authenticate to the REST API, and you cannot use an API access token to configure an SDK.
The following table compares SDK credentials and REST API access tokens:
As a LaunchDarkly customer, you must set up an SDK to integrate LaunchDarkly with your code.
When your application starts up, your code should initialize the LaunchDarkly SDK you’re working with. When a customer encounters a feature flag in your application, your code should use the SDK to evaluate the feature flag and retrieve the appropriate flag variation for that customer. We provide client-side, server-side, mobile, edge, and AI SDKs in a variety of languages to support your use case and tech stack.
The SDKs are specialized for the tasks of evaluating feature flags in your application and generating analytics events based on those evaluations. Constraining the SDKs to these use cases lets us keep them relatively small and easy to embed in your application.
To get started, read Setting up an SDK. To determine which type of SDK to use, read Choosing an SDK type. When you’re ready to begin your implementation, read Implementation guidelines for LaunchDarkly SDKs.
To configure a LaunchDarkly SDK, you need either an SDK key, a mobile key, or client-side ID for your SDK. These keys provide access to retrieve the flag data needed for evaluations, and to send analytics events. Which type of SDK you use in your application determines which key you need when you configure the SDK.
The keys are specific to each project and environment. You can view, copy, and reset SDK credentials from the SDK keys page under Settings.
To view or copy an SDK key, mobile key, or client-side ID:
LaunchDarkly SDKs are updated periodically. To learn more, read Versioning policy. To find the currently supported version of all SDKs, read Supported versions.
To learn more about a particular LaunchDarkly SDK, read the SDK reference guide for the SDK at Client-side SDKs, Server-side SDKs, or Edge SDKs. Each reference guide documents how to get started with the SDK, and links to information on the supported features, the SDK API documentation, the SDK’s GitHub repository, and sample applications that use the SDK.
As a LaunchDarkly customer, you’re never required to use the REST API or its associated client libraries. If you want to, you can perform all of the functions available in the REST API through the LaunchDarkly user interface (UI).
However, you may find it convenient to perform your feature management programmatically, rather than through the UI. For example, with the LaunchDarkly REST API you can perform the following:
To get started, read The LaunchDarkly API.
We do not recommend using the REST API to evaluate feature flags in your application’s code. For that, use the LaunchDarkly SDKs. The SDKs include features like caching of flag values and streaming of updates that you won’t receive automatically when using the REST API to evaluate flag values. To learn more, read Getting started with SDKs and Comparing LaunchDarkly’s SDKs and REST API.
To use the REST API, you need an API access token. You can generate access tokens in the Organization settings, from the Authorization page. Depending on your use case, you may prefer a personal access token or a service token. To authenticate to the LaunchDarkly API, add an Authorization header with your access token to your requests. To learn more, read API access tokens.
The LaunchDarkly REST API is updated frequently, to support the latest features in the LaunchDarkly product. If breaking changes to the API are required, we release a new version. To set the API version for each request, add an LD-API-Version header to the request. To learn more, read Versioning.
To get started using the LaunchDarkly API, read the tutorial Using the LaunchDarkly REST API. To learn more, read the API documentation.
Periodically, we auto-generate client libraries in several common languages based on the OpenAPI specification of our REST API. The client libraries allow you to make calls to the LaunchDarkly REST API endpoints directly from the language you’re already working in. To learn more, read OpenAPI and client libraries. To access the client libraries directly, visit the collection of client libraries on GitHub.
Outside of the official LaunchDarkly REST API, we occasionally provide supplemental API endpoints. These API endpoints:
To learn more about the currently available supplemental public APIs, read:
This guide discussed several ways you can interact with LaunchDarkly, including through the LaunchDarkly SDK, the LaunchDarkly REST API, client libraries, and other publicly available APIs. Understanding which of these options to use when helps you streamline the implementation of your application.