# Browser SDKs

The following items apply only to the following SDKs:
- Javascript Client SDK 
- React SDK
- Vue SDK

## Send events only for variation

Avoid sending spurious events when allFlags is called. Sending evaluation events for allFlags will cause flags to never report as stale and may cause inaccuracies in guarded rollouts and experiments with false impressions.

**Implementation**

- **MUST** Set `sendEventsOnlyForVariation: true` in the SDK options

**Validation**

- **Pass** calls to allFlags do not generate evaluation/summary events

## Bootstrapping strategy defined and implemented
Prevent UI flicker by rendering with known values before the SDK connects and retrieves flags. To learn more about bootstrapping, read [*Bootstrapping*](https://launchdarkly.com/docs/sdk/features/bootstrapping).

**Implementation**

- **SHOULD** Enable `bootstrap: 'localStorage'` or bootstrap from a server-side-SDK

**Validation**

- **Pass** if under offline/slow network the first paint uses bootstrapped values with no visible flash of wrong content.

<div class="page-metadata"><table class="page-metadata-table" aria-label="Page metadata"><thead><tr><th scope="col">Last modified</th><th scope="col">Last reviewed</th><th scope="col">Review due</th></tr></thead><tbody><tr><td><time datetime="2026-03-19">2026-03-19</time></td><td><time datetime="2026-02-13">2026-02-13</time></td><td><time datetime="2026-05-14">2026-05-14</time></td></tr><tr><td>Last commit: <a href="https://github.com/launchdarkly-labs/ps-flag-book/commit/d319a7d">d319a7d</a></td><td></td><td></td></tr></tbody></table></div>