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Documentation Index

Fetch the complete documentation index at: https://launchdarkly-preview.mintlify.app/llms.txt

Use this file to discover all available pages before exploring further.

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Overview

This topic documents how to get started with the Vercel SDK, and links to reference information on all of the supported features.
LaunchDarkly’s SDKs are open source. In addition to this reference guide, we provide source, API reference documentation, and a sample application:
ResourceLocation
SDK API documentationSDK API docs
Supported SDK VersionsVercel edge SDK
GitHub repositoryLaunchDarkly Vercel SDK
If you are using Vercel SDK version 1.2.0 or later, you can use the Vercel SDK by itself. The Vercel SDK sends events back to LaunchDarkly directly, however, you do need to configure the SDK to enable sending events. To learn more, read Configuration. If you are using an older version of the Vercel SDK, it is designed to be used with one of the LaunchDarkly client-side SDKs as follows:
  • The Vercel SDK gets all flags at the edge for a given context, and bootstraps them onto a cached payload
  • The client-side SDK initializes the bootstrapped payload
  • The client-side SDK evaluates the flags and sends events back to LaunchDarkly
Configure the Vercel integration to use this SDK successfully. To learn more, read Vercel.The Vercel integration is only available to customers on select plans. To learn more, read about our pricing. To upgrade your plan, contact Sales.
This topic covers how to get started with LaunchDarkly’s Vercel SDK.

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Get started

After you complete the Install a Vercel integration process in an existing project, follow these instructions to start using the LaunchDarkly Vercel SDK:
If you are already using Vercel’s Flags SDK, you can use that with your LaunchDarkly feature flags, your Vercel integration, and Vercel’s @flags-sdk/launchdarkly LaunchDarkly adapter. To learn how, read LaunchDarkly Flags SDK Example in Vercel’s documentation.

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Install the SDKFirst, install the Vercel SDK as a dependency in your application using your application’s dependency manager. Here’s how:

    yarn add @launchdarkly/vercel-server-sdk
Next, import the LaunchDarkly client in your application code: 
    import { init } from '@launchdarkly/vercel-server-sdk'
    import { createClient } from '@vercel/edge-config'

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Initialize the client

After you install and import the SDK, create an edge client using your Edge Config ID. Then, initialize an LDClient using your LaunchDarkly client-side ID and this edge client. Here’s how: 
    const edgeConfigClient = createClient(process.env.EDGE_CONFIG)
    const ldClient = init('example-client-side-id', edgeConfigClient)

    await ldClient.waitForInitialization()
The Vercel SDK requires a client-side ID. Client-side IDs are specific to each project and environment. They are not secret, and you can include them in code. Do not embed a server-side SDK key into an edge application.You can find client-side IDs in Project settings, on the Environments list. To learn more about key types, read Keys.
If you are using the Vercel SDK version 1.2.0 or later, you can optionally configure sending events during initialization. This enables Experimentation and metrics use cases. To learn more, read Experimentation and metric events. Here’s how: 
    const ldClient = init('example-client-side-id', edgeConfigClient, { sendEvents: true });
    await ldClient.waitForInitialization();

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Evaluate a flag

After you initialize the client, wait for the waitForInitialization function to resolve. When waitForInitialization is resolved, the client can serve feature flags. Using the client, you can check which variation a particular context will receive for a given feature flag. In your Vercel Edge application, place the variation code so that it is invoked as needed. Here is an example: 
    const ldContext = {
      kind: 'org',
      key: 'example-organization-key',
      someAttribute: 'example-attribute-value',
    }
    const flagValue = await ldClient.variation('example-flag-key', ldContext, true)

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Bootstrap flags with Next.js

If you are using Next.js with Vercel, you can bootstrap feature flags on the Root Layout for use in the LaunchDarkly React Web SDK. To bootstrap flags, specify the root layout’s runtime with a value of edge and pass the flags to a client component that initializes the LaunchDarkly React SDK.The Vercel SDK’s GitHub repository contains an example application that takes advantage of bootstrapping flags from the edge for use in the LaunchDarkly React Web SDK.

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Promises and async

All asynchronous SDK methods that return a Promise are compatible with then/catch or async/await. You can use either.

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Shut down the client

If you send events, you must flush those events before your worker exits to ensure that they are sent back to LaunchDarkly. To learn more, read Flushing events. Shut down the client when your application terminates. To learn more, read Shutting down.

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Supported features