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Last edited: May 01, 2024
FullStory SDK Requirements

The FullStory integration requires the LaunchDarkly JavaScript SDK version 2.24 or higher, or the React Web SDK version 2.27 or higher.


This topic explains how to set up and use the LaunchDarkly FullStory integration. The integration sends LaunchDarkly flag evaluations as FullStory page properties.

FullStory combines analytics with high-fidelity session replay and intelligent diagnostics so you can fix issues impacting your customers' experience, even if the issues are not reported by customers.

To learn more about the use case for this integration, read LaunchDarkly + FullStory: Targeted User Observability on the LaunchDarkly blog.

Set up the integration

The code below can be modified to fit your setup.

Here's how to get started:

  • Install and configure the FullStory client
  • Use the setVars API to send the evaluated flags to FullStory page properties

In the example below, evaluatedSessionFlags is a two-level map. The first key is the url path. The second key is the flag key. The final values are based on the return value of the feature flag:

// instantiate the path to flags mapping object outside of the Inspector
const evaluatedSessionFlags: { [path: string]: { [flagKey: string]: unknown } } = {};
const fsInspector: LDInspection {
type: 'flag-used',
name: 'fullstory-inspector',
method: (key: string, detail: LDEvaluationDetail) => {
// FullStory attaches getCurrentSessionURL and setVars to the window object.
if (window.FS === undefined || typeof window.FS.getCurrentSessionURL !== 'function') {
const url = window.FS.getCurrentSessionURL(true);
if (url === undefined) {
evaluatedSessionFlags[url] = {
[key]: detail.value,
const arrayOfFlags = Object.keys(evaluatedSessionFlags[url]).map(
(flagKey) => `${flagKey}=${JSON.stringify(evaluatedSessionFlags[url][flagKey], null, 1)}`,
if (typeof window.FS.setVars === 'function') {
window.FS.setVars('page', { ldflags: arrayOfFlags }, {integration:"launchdarkly"});
const options = { inspectors: [fsInspector] };
const client = LDClient.initialize('client-side-id-123abc', context, options);