Evaluation

Evaluation routes are public API routes for customer applications. Snapshot routes require FeatureGate-issued server runtime keys. POST /v1/evaluate accepts either a server runtime key or a publishable browser client key.

Use this page for integration guidance and exact generated request and response details. The standalone reference pages are still available for deep links: POST /v1/evaluate, GET /v1/snapshot, and GET /v1/snapshot/stream.

Authentication

Send the key as a bearer token. Server runtime keys are scoped to a single environment and carry only the runtime scopes you grant them: runtime:snapshot and/or runtime:evaluate.

Browser client keys can use only client:evaluate. They must be called from an allowed Origin and can evaluate only flags explicitly exposed to clients in that environment.

Use server runtime keys for backend applications and the server TypeScript SDK. Use publishable client keys only from browser code. Client keys are not accepted by /v1/snapshot or /v1/snapshot/stream, and they never expose targeting rules or full environment snapshots.

Evaluate

POST /v1/evaluate resolves one or more flags for a given context in a single round trip. Use it from servers when you do not want to hold a local snapshot, or through the browser and React SDKs when you need client-side checks for exposed flags.

curl https://api.featuregate.dev/v1/evaluate \
-H "Authorization: Bearer fg_sk_test_0123456789abcdef0123456789abcdef0123456789abcdef" \
-H "Content-Type: application/json" \
-d '{
  "evaluations": [
    { "key": "new-checkout", "defaultValue": false }
  ],
  "context": {
    "user": { "id": "user_123" },
    "account": { "plan": "pro" }
  }
}'

curl -X POST https://api.featuregate.dev/v1/evaluate \
  -H "Authorization: Bearer fg_sk_test_0123456789abcdef0123456789abcdef0123456789abcdef" \
  -H "Content-Type: application/json" \
  -d '{
  "evaluations": [
    {
      "key": "new-checkout",
      "defaultValue": false
    }
  ],
  "context": {
    "user": {
      "id": "user_123"
    },
    "account": {
      "plan": "pro"
    }
  }
}'

{
  "evaluation": {
    "projectId": "project_example",
    "environment": {
      "id": "env_example",
      "key": "production",
      "name": "Production"
    },
    "results": [
      {
        "key": "new-checkout",
        "type": "boolean",
        "value": true,
        "reason": "targeting_match"
      }
    ]
  }
}

When called with a browser client key, the request must include an Origin that exactly matches the key's allowed-origin list. Unexposed flags behave like missing flags and return the caller-provided default.

Snapshot and ETags

Use GET /v1/snapshot for local evaluation. Snapshot responses include an ETag and support If-None-Match, so unchanged snapshots collapse to a cheap 304.

/v1/snapshot/stream is an optional invalidation channel, not the source of truth. The SDK still reconciles against the snapshot endpoint.

curl -X GET https://api.featuregate.dev/v1/snapshot \
  -H "Authorization: Bearer fg_sk_test_0123456789abcdef0123456789abcdef0123456789abcdef"

{
  "snapshot": {
    "version": "snapshot_version_example",
    "projectId": "project_example",
    "environment": {
      "id": "env_example",
      "key": "production",
      "name": "Production"
    },
    "flags": []
  }
}

curl -X GET https://api.featuregate.dev/v1/snapshot/stream \
  -H "Authorization: Bearer fg_sk_test_0123456789abcdef0123456789abcdef0123456789abcdef"

{
  "projectId": "project_example",
  "version": "snapshot_version_example",
  "generatedAt": "2026-06-18T00:00:00.000Z",
  "environment": {
    "id": "env_example",
    "key": "production",
    "name": "Production"
  }
}