Flagship Rollout

Evaluate Cloudflare Flagship feature flags at the edge via a Workers binding. Returns boolean values or detailed evaluation metadata for targeting experiments.

API ReferenceCopy Anchor Link

GET /flags/:keyCopy Anchor Link

Evaluate a boolean flag.

key string (required, path)

Flag key.

userId string (optional)

Targeting context attribute.

default string (optional)

Fallback boolean as true or false (default false).

Example RequestCopy Anchor Link

curl "https://your-worker.workers.dev/flags/new-checkout?userId=user-42&default=false"

Success ResponseCopy Anchor Link

{
  "flagKey": "new-checkout",
  "value": true,
  "context": { "userId": "user-42" }
}

GET /flags/:key/detailsCopy Anchor Link

Same query params. Returns evaluation details (variant, reason, errorCode, etc.).

Example RequestCopy Anchor Link

curl "https://your-worker.workers.dev/flags/new-checkout/details?userId=user-42"

Error CodesCopy Anchor Link

• 400 - Missing or invalid flag key (INVALID_FLAG_KEY)
• 502 - Flag evaluation failure (FLAG_ERROR)

Use CasesCopy Anchor Link

• Learn Flagship Workers bindings and targeting context
• Gate features by user id at the edge
• Inspect evaluation reason / variant for debugging rollouts
• Prototype A/B or percentage rollouts before wiring into an app

LimitationsCopy Anchor Link

• Requires a real Flagship app_id in wrangler.json
• Demo evaluates boolean flags only
• Local wrangler dev talks to the live Flagship app for that app_id
• No dashboard UI in this Worker - evaluation API only

DeploymentCopy Anchor Link

curl "https://your-worker.workers.dev/flags/new-checkout?userId=user-42"

Local DevelopmentCopy Anchor Link

cd apps/experiments/flagship-rollout
npm install
npm run dev

curl "http://localhost:8787/flags/new-checkout?userId=user-42&default=false"

ConfigurationCopy Anchor Link

wrangler.json declares:

• Flagship binding FLAGS with app_id

Cloudflare Features UsedCopy Anchor Link

• Workers - Edge compute runtime
• Flagship - Feature flags at the edge