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Overview

FlagSync’s client-side SDKs are designed for single-user contexts like web and mobile apps:

JavaScript

User segment targeting rule creationFor browser-based apps (e.g., SPAs, vanilla JS).

React

User segment targeting rule creationFor React-based web applications.
Need another language or framework? Contact FlagSync Support to explore adding it to our roadmap.

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Avoid Flickering During SDK Initialization

When using feature flags in web applications, rendering a page with default flag values before the SDK initializes can cause a “flicker” as content updates. To prevent this, consider these strategies:
  • Initialize Early: Prioritize the SDK initialize to evaluate flags sooner, minimizing delays.
  • Delay Rendering: Hide the page (e.g., set body to display: none, or use the waitForReady prop in the React SDK) until the SDK signals readiness, then show the correct content.
    SDK initialization time, usually 30-50 milliseconds, depends on flag count and ruleset complexity.
  • Bootstrap Flags: Provide initial flag values for immediate use, avoiding fetch delays.
    See Bootstrapping for details on providing initial flag values.

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Next Steps

Get started with client-side SDKs: