Overview

Flag Evaluation Flow

FlagSync evaluates flags using the same logic flow across SDKs:

Is the SDK ready?

If not, the SDK returns the defaultValue (e.g., false) or control string.

// Before SDK is ready
const one = client.flag('flag-one', false); // false (defaultValue)
const two = client.flag('flag-two'); // "control"
await client.waitForReady();

Client-side SDKs can bootstrap via LocalStorage or from an initial flag set, using those values until the SDK initializes with server data.

Does the flag key exist?

If the flag key isn’t found, the SDK returns the defaultValue or control.

// Unknown flag, returns true (defaultValue)
const value = client.flag('foobarbaz', true);

If the flag key was included in the bootstrapped values, this value will be returned.

Is the flag disabled?

If disabled: The default “off” variant is returned, halting further evaluation.
If enabled: The algorithm proceeds to targeting and rollout checks.

Explore Flags: All Users to learn about default variants.

Does the flag have Targeting Rules?

See Targeting for evaluation logic.
See Flags: User Segments to learn about targeting rules.

Does the flag have a Percentage Rollout?

See Rollouts for evaluation logic.
See Flags: Percentage Rollouts to learn about rollouts.

Fallback

Returns the “on” variant if no rules or percentages apply.

See Flags: All Users to learn about default variants.

Flow Diagram

Next Steps

Dive deeper into the flag evaluation process:

Learn targeting logic in Targeting.
Explore rollout evaluation in Rollouts.
Start with Quickstart: SDK

TargetingLearn how FlagSync applies targeting rules during flag evaluation.

Getting Started

CLI

Client-Side

Server-Side

Flag Evaluation Flow

Flow Diagram

Next Steps

​Flag Evaluation Flow

​Flow Diagram

​Next Steps

Flag Evaluation Flow

Flow Diagram

Next Steps