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Evaluate

Evaluate feature flags for a given context

Last updated: May 19, 2026

This endpoint is what the Feature Flags SDK calls under the hood. You can call it directly if you’re not using the SDK or need to evaluate flags from a language without an SDK.

Evaluate Flags

POST /v1/flags/evaluate Secret key

Evaluate all feature flags for a property and environment, applying targeting rules against the provided context.

Parameter	Type	Required	Description
propertyId (body)	string	✓	Property to evaluate flags for
environment (body)	string	✓	Environment name (e.g., production, staging)
context (body)	object		Evaluation context for targeting rules

Response

{
  "flags": {
    "new-checkout": {
      "value": true,
      "type": "boolean"
    },
    "cta-color": {
      "value": "green",
      "type": "string"
    }
  }
}

Example

bash

curl -X POST "https://api.sessionsight.com/v1/flags/evaluate" \
  -H "x-api-key: YOUR_SECRET_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "propertyId": "",
  "environment": "",
  "context": ""
}'

Context Object

The context object is used to evaluate targeting rules. Any key-value pairs can be included. They’re matched against the conditions you configure in the dashboard.

Common Fields	Type	Description
`userId`	`string`	Your user ID. Used for percentage rollouts and user targeting
`visitorId`	`string`	SessionSight visitor ID. Enables segment-based targeting
Custom fields	`string \\| number \\| boolean`	Any additional properties for targeting rules

Never send PII (emails, phone numbers, addresses, etc.) in the context object. Use opaque identifiers like user IDs instead.

Response Format

The response contains a flags object where each key is a flag key and the value includes:

Field	Type	Description
`value`	`boolean \\| string`	The evaluated flag value
`type`	`string`	Either `"boolean"` or `"string"`

Only flags that are enabled in the requested environment are returned. Disabled flags are omitted, so your SDK or code should use default values for missing keys.

How Evaluation Works

All enabled flags for the property + environment are loaded
For each flag, targeting rules are evaluated top-to-bottom against the context
The first matching rule determines the flag’s value
If no rules match, the flag’s default value is used
If the flag is disabled in this environment, it’s omitted from the response