Introduction

Vibe Flags is an open-source feature flag library for the browser. It runs entirely client-side — no backend, no accounts, no API keys. Add one <script> tag and declare flags in plain HTML.

Why Vibe Flags?

Most feature flag tools (LaunchDarkly, Unleash, PostHog) are built for production rollouts at scale. They require servers, SDKs, dashboards, and accounts.

Vibe Flags takes a different approach. It's built for:

• Prototyping and vibe-coding — try multiple UI variants without touching git
• AI-assisted development — flags are plain HTML that any LLM can read and write
• Static sites and demos — no backend needed, works offline
• Learning and experimentation — zero setup, instant feedback

How it works

1. You add flag components to your HTML (<vibe-flags-boolean>, <vibe-flags-select>)
2. Each flag self-registers when it connects to the DOM
3. The <vibe-flags-toolbar> discovers all flags and renders toggle controls
4. Flag state is persisted in localStorage — values survive page refreshes

No build step. No framework required. No JavaScript to write.

Key features

• ~11KB gzipped with zero runtime dependencies
• Web Components — works in any framework or plain HTML
• Boolean and select flags — toggles and multi-option switches
• Draggable toolbar — floating panel that auto-discovers all flags
• localStorage persistence — state survives refreshes and syncs across tabs
• URL overrides — share exact flag states via query parameters
• React integration — dedicated hooks and components
• TypeScript — full type safety and imperative store API
• AI-friendly — plain HTML API that LLMs understand natively

What it's not

Vibe Flags is not a replacement for production feature flag systems. It doesn't have:

• Server-side evaluation
• User targeting or percentage rollouts
• Audit trails or team permissions
• Analytics or A/B testing

If you need those things, see the Comparison page. For everything else, Vibe Flags gets you running in 30 seconds.