Target anonymous visitors

An anonymous visitor is anyone using your app without being signed in: a marketing-page reader, a trial user before signup, or any app that doesn’t use Bridge auth at all. Flags still work for them, including percentage rollouts and A/B tests, because the SDK manages identity for you.

The anonymous ID

On first load, the SDK generates an anonymous ID (a UUID prefixed anon_) and persists it in the browser, so the same visitor presents the same identity on every page view and every return visit. With Bridge auth enabled, the signed-in identity takes over automatically, and the SDK reports the previous anonymous ID alongside the user ID so pre-login activity can be linked to the signed-in user.

Stable bucketing

Percentage rollouts need to answer “is this visitor in the 10%?” the same way every time. That’s what stable bucketing means: the SDK hashes the flag key together with the visitor’s identity into a bucket number from 0 to 99, and a rule with a rollout percentage passes when the bucket falls below it. Because the hash inputs never change for a given visitor and flag, the same visitor always lands in the same bucket:

• No flicker: a visitor doesn’t flip between the old and new experience across page loads or sessions.
• Sticky ramps: a visitor who’s in at 10% stays in as you ramp to 25%, 50%, 100%. Nobody gets re-rolled.
• Consistent everywhere: the same hash runs on the server and in the SDK, so both sides agree when you propagate context to your backend.

Where persistence is configured

By default the anonymous ID is stored in localStorage under the key bridge.anon_id, so it survives across sessions. If you need different behavior, the advanced createBridgeFlags API accepts an identity option:

• tracking: 'persistent': localStorage, survives across sessions (the default)
• tracking: 'session': sessionStorage, one browser tab/session
• tracking: 'none': in-memory only, forgotten on reload
• storage: your own IdentityStorage implementation (e.g. cookie-backed)
• storageKey: a different storage key than bridge.anon_id

Most apps never touch this; the default <BridgeProvider> wiring uses persistent tracking.

Example: roll out to 20% of visitors

Create a flag new_landing in Control Center (your admin dashboard at app.thebridge.dev) and give it a rule with a rollout percentage of 20 and no attribute conditions. Then read it like any other flag:

import { useFlag } from '@nebulr-group/bridge-react/flags';

function Landing() {
  const landing = useFlag('new_landing', false);

  return landing.value ? <NewLanding /> : <OldLanding />;
}

Every visitor, signed in or not, gets bucketed by their stable identity: roughly 20% see the new page, and each individual visitor keeps seeing the same version. Ramping to 50% or 100% later is a Control Center edit, not a deploy.

A rollout can also sit behind attribute conditions (say, 20% of visitors whose locale = sv), because the percentage applies after the rule’s conditions match. And a multi-variant flag (string/number/JSON) splits traffic into experiment arms with the same stickiness, which is how you run A/B tests on visitors who have never signed in.