Evaluate Experiments
Evaluates experiments and feature flags for a subject and records an exposure. Pass flag_key to evaluate one flag, or omit it to evaluate every active flag in the account and related resource scope. Requires no authentication; when a credential resolves, its authentication method, API key ID, and signed-in user ID are recorded on the exposure event.
Authorizations
An Account API key, an App API key, an account access token, an account-scoped user token, or a user OAuth token. Prepend the key or token with Bearer, for example Bearer ***************************. See Auth & API keys for how to get each one.
Headers
Pins the request to a dated API version.
"2026-10-15-1"
Query Parameters
Bucketing subject: the user, account, or anonymous ID the experiment's bucket_by assigns on. Only the identity matching bucket_by is used; when it is missing, evaluating a single flag fails and a batch omits that experiment. Subjects outside every treatment range receive control. subject[account_id] also enables account-level targeting rules. Experiment ownership comes from the top-level account_id.
Restricts batch evaluation to this related resource; omitted batches contain only unbound experiments.
Flag or experiment to evaluate — the flag_key handle or the expt_ id. Omit to return all flags the caller qualifies for.
Owning account ID. Required when evaluating by flag_key or in a batch; optional for an expt_ ID.
Set false to read an assignment without recording an exposure, such as when a client caches assignments up front and records the exposure when the arm is rendered. Omitted records the exposure.
Response
single flag evaluated
- Option 1
- Option 2
Whether the subject receives a treatment or enabled feature flag.
true
Treatment name, control, or null for an inactive flag or excluded subject.
"treatment"
Unique experiment ID, included for account experiments.
Present when evaluating a single experiment.
"checkout_redesign"

