Get Experiment Assignment

REST reference for POST /experiments/assignments/{experiment_key} — the server-side variant assignment endpoint. Sticky on visitor_id, optionally records an impression.

Return the server-side variant assignment for a visitor in a single A/B or multivariate experiment, identified by its experiment key. Bucketing is deterministic on visitor_id and is sticky across calls. Tracking an impression is the default — pass track_impression: false to read without recording. The browser SDK and this endpoint converge on the same variant for the same visitor.

See the Server-Side Experimentation guide for end-to-end recipes.

Path Parameters

experiment_key*string

The experiment's stable key. Surfaced in the dashboard under each experiment's setup tab.

Request Body

application/json

Visitor + optional page context for eligibility.

TypeScript Definitions

Use the request body type in TypeScript.

token*string

The experiment token (exp_*) for the experiment settings holding this experiment. Available from the dashboard.

visitor_id*string

Stable identifier for the visitor — typically the Ours visitor id from your browser cookie, or your own server-side user id if you keep the same id consistent across browser and server.

Length1 <= length <= 400

context?|

Optional page context for URL + query-param eligibility. Variant bucketing is deterministic on visitor_id regardless of context.

track_impression?|

When true (default), an $experiment_impression event is enqueued and the visitor's experiment_assignments map is updated. Set to false to read the assignment without recording an impression — useful for in-test diagnostics.

Response Body

`application/json`

curl -X POST "https://example.com/experiments/assignments/string" \  -H "Content-Type: application/json" \  -d '{    "token": "string",    "visitor_id": "string"  }'

{  "success": true,  "in_experiment": true,  "experiment_id": "string",  "experiment_key": "string",  "experiment_name": "string",  "variant_id": "string",  "variant_name": "string",  "is_control": true,  "type": "string",  "redirect": "string"}

{  "success": false}

{  "success": false}

{  "success": false}

{  "success": false}

Get Experiment Assignment

Path Parameters

Request Body

Response Body

200application/json

400application/json

401application/json

404application/json

500application/json

`application/json`

`application/json`

`application/json`

`application/json`

`application/json`