@vercel/flags

4.0.1

Patch Changes

d4108c8: - expose clearDedupeCacheForCurrentRequest to allow clearing the cache of a deduped function for the current request

4.0.0

Major Changes

bc7944e: BREAKING CHANGES The general purpose encrypt and decrypt functions were replaced by dedicated functions, and it is now required to return version information from the flags discovery endpoint. See the Upgrade Guide for upgrade instructions.

Minor Changes

bc7944e: Add createFlagsDiscoveryEndpoint helper functions when creating the /.well-known/vercel/flags endpoint for Next.js App Router and SvelteKit.

3.2.0

Minor Changes

701f3c2: feat: provide precompute patterns for SvelteKit

3.1.2

Patch Changes

b79a84a: Pass the defaultValue to the adapter's decide function

3.1.1

Patch Changes

6955b68: emit reduced console info when falling back to defaultValue during development
cf532da: Update package.json and tsup.config.js for flags package

3.1.0

Minor Changes

76feb16: Add mergeProviderData function to @vercel/flags.

This function allows merging ProviderData from multiple sources.

This is handy when you declare feature flags in code, and want to extend those definitions with data loaded from your feature flag provider.

import { verifyAccess, mergeProviderData, type ApiData } from '@vercel/flags';
import { getProviderData } from '@vercel/flags/next';
import { NextResponse, type NextRequest } from 'next/server';
import { getProviderData as getStatsigProviderData } from '@flags-sdk/statsig';
import * as flagsA from '../../../../flags-a'; // your feature flags file(s)
import * as flagsB from '../../../../flags-b'; // your feature flags file(s)

export async function GET(request: NextRequest) {
  const access = await verifyAccess(request.headers.get('Authorization'));
  if (!access) return NextResponse.json(null, { status: 401 });

  const providerData = await mergeProviderData([
    // expose flags declared in code first
    getProviderData({ ...flagsA, ...flagsB }),
    // then enhance them with metadata from your flag provider
    getStatsigProviderData({ consoleApiKey: '', projectId: '' }),
  ]);

  return NextResponse.json<ApiData>(providerData);
}

Patch Changes

2713ea7: Handle undefined values
- fix: Fall back to defaultValue when a feature flag returns undefined
- fix: Throw error when a flag resolves to undefined and no defaultValue is present
The value undefined can not be serialized so feature flags should never resolve to undefined. Use null instead.

Fix exports
- fix: Export Identify and Decide types

3.0.2

Patch Changes

708d5e2: generatePermutations: infer options of boolean flags

3.0.1

Patch Changes

7e21d4f: add metadata to package.json

3.0.0

Major Changes

db89f0d: - BREAKING CHANGE removed all unstable_ prefixes, e.g. unstable_flag is now flag
- BREAKING CHANGE removed getPrecomputationContext, use dedupe instead (see below)
- BREAKING CHANGE moved all provider functions to dedicated packages
  - @vercel/flags/providers/launchdarkly → @flags-sdk/launchdarkly
  - @vercel/flags/providers/statsig → @flags-sdk/statsig
  - @vercel/flags/providers/split → @flags-sdk/split
  - @vercel/flags/providers/hypertune → @flags-sdk/hypertune
  - @vercel/flags/providers/optimizely → @flags-sdk/optimizely
  - @vercel/flags/providers/happykit → @flags-sdk/happykit
- BREAKING CHANGE changed .run({}) behavior
See flags-sdk.com for the latest APIs.
db89f0d: remove unstable_ prefixes

Minor Changes

db89f0d: @vercel/flags/next: Added a dedupe function

dedupe is a middleware-friendly version of React.cache. It allows ensuring a function only ever runs once per request.
```
import { dedupe } from '@vercel/flags/next';

let i = 0;
const runOnce = dedupe(async () => {
  return i++;
});

await runOnce(); // returns 0
await runOnce(); // still returns 0
```
This function is useful when you want to deduplicate work within each feature flag's decide function. For example if multiple flags need to check auth you can dedupe the auth function so it only runs once per request.

dedupe is also useful to optimistically generate a random visitor id to be set in a cookie, while also allowing each feature flag to access the id. You can call a dedupe'd function to generate the random id within your Edge Middleware and also within your feature flag's decide functions. The function will return a consistent id.
```
import { nanoid } from 'nanoid';
import { cookies, headers } from 'next/headers';
import { dedupe } from '@vercel/flags/next';

/**
 * Reads the visitor id from a cookie or returns a new visitor id
 */
export const getOrGenerateVisitorId = dedupe(
  async (): Promise<{ value: string; fresh: boolean }> => {
    const visitorIdCookie = (await cookies()).get('visitor-id')?.value;

    return visitorIdCookie
      ? { value: visitorIdCookie, fresh: false }
      : { value: nanoid(), fresh: true };
  },
);
```
Note: "once per request" is an imprecise description. A deduped function actually runs once per request, per compute instance. If a dedupe'd function is used in Edge Middleware and in a React Server Component it will run twice, as there are two separate compute instances handling this request.

Note: This function acts as a sort of polyfill until similar functionality lands in Next.js directly.

2.7.0

Minor Changes

fb50709: Adds support for using feature flags in Pages Router.

The same feature flag declared for App Router can now also be used in Pages Router. Feature flags need to be used server-side.

Note that your implementation of the actual feature flag needs to be compatible with Pages Router if you plan on using it inside of Pages Router. This means you can not call functions like headers() and cookies() which are not available in Pages Router. You can instead rely on the headers and cookies arguments passed to your decide function as decide({ headers, cookies }).

Dynamic usage example

export async function getServerSideProps({ req }) {
  const showFreeDeliveryBanner = await showFreeDeliveryBannerFlag(req);
  return { props: { showFreeDeliveryBanner } };
}

Precomputed usage example

import { bannerFlags, showFreeDeliveryBannerFlag } from './flags';
import type {
  GetStaticPaths,
  GetStaticProps,
  InferGetStaticPropsType,
} from 'next';
import { unstable_generatePermutations as generatePermutations } from '@vercel/flags/next';

export const getStaticPaths = (async () => {
  const codes = await generatePermutations(bannerFlags);

  return {
    paths: codes.map((code) => ({ params: { code } })),
    fallback: 'blocking',
  };
}) satisfies GetStaticPaths;

export const getStaticProps = (async (context) => {
  const showFreeDeliveryBanner = await showFreeDeliveryBannerFlag(
    context.params!.code as string,
    bannerFlags,
  );

  return { props: { showFreeDeliveryBanner } };
}) satisfies GetStaticProps<{ showFreeDeliveryBanner: boolean }>;

87503b6: Return createdAt and updatedAt as part of the provider data for those that support it

2.6.3

Patch Changes

69f8df0: use defaultValue when an async decide function throws
65d3d73: add MIT license

2.6.2

Patch Changes

80e0737: Add Next.js 15 compatibility.

Uses the async versions of headers and cookies to avoid warnings during development.

2.6.1

Patch Changes

9c379a8: add pagination to LaunchDarkly provider

2.6.0

Minor Changes

7b9aa17: evaluate flags once per request only by reusing the result
b049c26: add SvelteKit support

Patch Changes

c12f4d4: Deprecates FlagsReporter and injectFlags.

Web Analytics now automatically detects flags present in the DOM, so these are no longer necessary.

You can safely remove FlagsReporter and any calls to injectFlags.
1be4799: add no-store to LaunchDarkly provider

2.5.1

Patch Changes

3a68cf7: Simplify middleware usage

BREAKING CHANGE: unstable_precompute now returns code directly

Before

const values = await unstable_precompute(precomputeFlags, context);
const code = await unstable_serialize(precomputeFlags, values);

After

This can now be done in a single function call.

const code = await unstable_precompute(precomputeFlags, context);

Other notes

unstable_precompute conceptually calls unstable_evaluate and unstable_serialize to generate the code.

This can also be done manually if you need access to values:

const values = await unstable_evaluate(precomputeFlags, context);
const code = await unstable_serialize(precomputeFlags, values);

It's also possible to get the value of a specific flag in middleware based on the precomputation:

// flags.ts
export const showBanner = flag({
  /* ... */
});
export const precomputeFlags = [showBanner /* ... */];

// middleware.ts
const code = await unstable_precompute(precomputeFlags, context);
const banner = showBanner(code, precomputeFlags);

2.5.0

Minor Changes

1003c29: add experimental @vercel/flags/next pattern for working with feature flags in Next.js

2.4.0

Minor Changes

c132300: Add reportValue function to report resolved flags
5911721: add HappyKit provider
bf47adb: Provide a the unstable_getFlagsProps and unstable_setGlobalFlagsAnalyticsKeys functions that can be used to integrate with Vercel Analytics

2.3.0

Minor Changes

be714bd: add hypertune provider

2.2.1

Patch Changes

6f401cc: update README

2.2.0

Minor Changes

a6883ad: Add Optimizely provider
af787a9: Include Experiments from Statsig in getStatsigData

Patch Changes

ae3f59c: Fix pagination for Statsig provider in getStatsigData

2.1.2

Patch Changes

b22ab52: support undefined as authHeader in verifyAccess for Pages Router compatibility
155d5ac: make overrideEncryptionMode optional in ApiData type

2.1.1

Patch Changes

6b79659: expose ApiData type

2.1.0

Minor Changes

abae5af: Add verifyAccess to allow skipping encryption on the .well-known/vercel/flags endpoint

2.0.0

Major Changes

59befe1: Unify encrypt and decrypt functions

BREAKING CHANGE Replace the existing calls to any encrypt* or decrypt* functions like encryptApiData, encryptOverrides, encryptValues or decryptApiData, decryptOverrides, decryptValues with encrypt or decrypt

1.1.2

Patch Changes

9ff283b: Fix auto-import showing @vercel/flags/* as option

1.1.1

Patch Changes

80a1acc: Fix type export for providers

1.1.0

Minor Changes

1f4fb18: Add Statsig and Split providers and update exports in package.json

1.0.0

Major Changes

c1e29ea: BREAKING CHANGE: VERCEL_FLAGS_SECRET env var has been renamed to FLAGS_SECRET
- Rename your VERCEL_FLAGS_SECRET environment variable to FLAGS_SECRET in your project settings on vercel.com
- Pull down the latest environment variables using vercel env pull .env.local

0.2.1

Patch Changes

794b711: prevent xss

0.2.0

Minor Changes

11a4bb6: add LaunchDarkly provider

0.1.9

Patch Changes

1808b9c: fix auto-import in vs code defaulting to wrong path

0.1.8

Patch Changes

91f801d: add JSDoc to FlagDefinitionsType, FlagValuesType and FlagOverridesType

Package detail

readme

changelog

@vercel/flags

4.0.1

Patch Changes

4.0.0

Major Changes

Minor Changes

3.2.0

Minor Changes

3.1.2

Patch Changes

3.1.1

Patch Changes

3.1.0

Minor Changes

Patch Changes

3.0.2

Patch Changes

3.0.1

Patch Changes

3.0.0

Major Changes

Minor Changes

2.7.0

Minor Changes

2.6.3

Patch Changes

2.6.2

Patch Changes

2.6.1

Patch Changes

2.6.0

Minor Changes

Patch Changes

2.5.1

Patch Changes

2.5.0

Minor Changes

2.4.0

Minor Changes

2.3.0

Minor Changes

2.2.1

Patch Changes

2.2.0

Minor Changes

Patch Changes

2.1.2

Patch Changes

2.1.1

Patch Changes

2.1.0

Minor Changes

2.0.0

Major Changes

1.1.2

Patch Changes

1.1.1

Patch Changes

1.1.0

Minor Changes

1.0.0

Major Changes

0.2.1

Patch Changes

0.2.0

Minor Changes

0.1.9

Patch Changes

0.1.8

Patch Changes

0.1.7

Patch Changes

0.1.6

Patch Changes

0.1.5

Patch Changes

0.1.4