Vercel Flags

6/22/2026

Introduces Vercel Flags, a platform-native feature flagging system. Details server-side evaluation for zero performance impact, automatic flag registration from code, and the 'Precompute' pattern for static page variants. Also covers agent-native management via CLI and browser-based testing with Flags Explorer. Highlights internal usage by v0 for feature releases, AI model routing, and database migrations.

5/7/2025

Introduces the Flags Explorer for managing feature flags directly from the Vercel Toolbar, enabling session-specific overrides for testing and demos. Adds a new Experimentation category to the Vercel Marketplace, featuring integrations with providers like Statsig, which syncs flags to Vercel's Edge Config for low-latency evaluation. Updates the open-source Flags SDK with a new adapters architecture to simplify integration with various feature flag providers, including specific support for Statsig.

11/25/2024

This post details how Notion uses Vercel Flags, integrated with Statsig and Edge Config, to run hundreds of experiments per year. It highlights the benefits of seamless integration, real-time experimentation at the edge, reduced payload sizes and latency, and improved Core Web Vitals (specifically CLS). The Vercel Toolbar's role in enabling both developers and non-developers to toggle experiments is also emphasized.

8/1/2024

This post details how Beyond Menu integrated Hypertune with Vercel's Edge Config to achieve zero-latency reads for feature flags and A/B tests. This involved syncing Hypertune's Hyperlang configurations into Edge Config, allowing the Hypertune SDK to initialize and fetch updates directly from Edge Config. This approach addresses challenges with traditional feature flag SDKs in serverless/edge environments, such as unreliable updates, initialization bottlenecks, and layout shifts in the browser. The integration also leverages type-safe auto-generated clients from Hypertune for compile-time error checking and improved developer experience.

7/26/2024

Introduces the new Flags SDK for Next.js and SvelteKit, which acts as an abstraction layer between applications and feature flag providers. It emphasizes server-side evaluation, the concept of feature flags as functions, and the inability to pass arguments on the call side to ensure consistent flag resolution and simplify migration and deletion. The post details basic flag declaration, progressions of usage with tradeoffs (hardcoded values vs. redeployments), and integration with the Vercel Toolbar for overrides. It also touches upon precomputing flags for static pages and using Edge Middleware for routing.

5/24/2024

This post details the integration of Vercel Flags with Vercel Web Analytics and logs, allowing for analysis of feature flag impact on page views and custom analytics events. It also introduces a new experimental design pattern for working with flags in Next.js and SvelteKit to improve server-side experimentation.

5/23/2024

This post introduces deeper integrations for feature flags within Vercel's Developer Experience Platform. Key contributions include: 1. Overriding feature flags directly from the Vercel Toolbar via an API Route and DOM scanning, with overrides stored in encrypted cookies. 2. Integration with Vercel Web Analytics and Runtime Logs to filter and break down data by feature flags, providing context for debugging and analysis. 3. A "feature flags as code" design pattern using `@vercel/flags/next` and `@vercel/flags/react` to enable server-side experimentation and precompute flag values for routing decisions in Middleware, aiming to eliminate client-side "jank".

3/6/2024

Introduces the ability to override feature flags directly from the Vercel Toolbar, integrating with external providers (LaunchDarkly, Optimizely, Statsig, Hypertune, Split) and custom setups. This feature allows for session-specific flag overrides to improve QA and development workflows. Implementation involves rendering flag values via a script tag (e.g., using `@vercel/flags/react`) and defining flag metadata via an API route (e.g., `.well-known/vercel/flags/route.ts`). Overrides are respected by reading the `vercel-flag-overrides` cookie.

6/27/2023

This post introduces an integration with LaunchDarkly to leverage Vercel Edge Config for low-latency, global feature flags. It details how LaunchDarkly configurations can be synced to Edge Config and consumed via a new `@launchdarkly/vercel-server-sdk` package. The integration enables near-instant flag updates without redeployments, with Edge Config lookups typically returning in under 15ms. A code example demonstrates bootstrapping the LaunchDarkly client from Edge Config for conditional UI rendering.

4/6/2023

Introduces Vercel Edge Config, a globally distributed, ultra-low latency data store for configuration data, optimized for fast reads and infrequent writes. This enables dynamic data storage alongside functions, with data replicated to all Vercel regions for instant availability. It allows for near-zero latency experimentation (0ms to 10ms lookups) and dynamic changes without new deployments. Integrates with experimentation tools like LaunchDarkly, Statsig, and Split. Also details dynamic routing with Edge Middleware using Edge Config for blocking IPs/user-agents and advanced security rules.

3/23/2023

This post details the implementation of a zero-CLS A/B testing engine using Next.js and Vercel Edge Config. It introduces a system for creating type-safe experiments, pre-rendering experiment variations using dynamic routes and `getStaticPaths`/`getStaticProps`, and serving experiments to users via Next.js Middleware rewrites powered by Edge Config. The engine ensures users remain in their experiment bucket using cookies and captures events with a React Context. It also addresses the challenge of long build times by generating a limited number of experiment combinations.