With feature flags, developers can implement staged rollouts, focused releases, remote configuration, A/B testing, and quickly turn off features as needed, regardless of where they are running the feature flags. However, when using feature flags on the client side of a website or application, there are technical aspects to consider, particularly with Javascript SDKs. Local evaluation involves sending the feature flagging payload directly to the browser, while remote evaluation requires a network call to a service to determine which features should be enabled for a user. Both methods have pros and cons, including speed and security considerations. To address these concerns, GrowthBook offers features such as payload encryption, secure attribute hashing, and hiding experiment names, which can help protect sensitive data and ensure the integrity of feature flagging. Remote evaluation is slower than local evaluation but provides complete control over feature flag states and enables more dynamic lookups based on user identifiers. Ultimately, using feature flags on the client side adds valuable functionality to a site or application.