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Records analytics events from a client SDK.

POST
/v1/client/events
 
curl --request POST \
  --url https://eval.featureflip.io/v1/client/events \
  --header 'Authorization: <Authorization>' \
  --header 'Content-Type: application/json' \
  --data '{ "events": [ { "type": "Evaluation", "flagKey": "example", "userId": "example", "variation": "example", "timestamp": "2026-04-15T12:00:00Z", "metadata": { "additionalProperty": "example" }, "prerequisiteKey": "example" } ] }'

The client-surface counterpart of POST /v1/sdk/events, for SDKs that authenticate with a client key. The mobile SDKs (Swift, Android, Flutter) use this to report track() calls. Server SDKs keep using /v1/sdk/events.

Flag evaluations do not arrive here: this API evaluates on a client SDK’s behalf and records those evaluations itself, on evaluate and identify. Both sources feed the same analytics.

Because a client key is public by design, this endpoint is rate limited per client IP, limits the size of a request, and caps the number of events in one request. An event that exceeds one of the following per-event limits is discarded on its own; the rest of the batch is still recorded, and the response is unchanged:

  • its timestamp sits far outside the present;
  • its flagKey is longer than 256 characters;
  • it is a Custom event introducing more than 50 distinct event keys in one request. Repeats of a key already in the request are always recorded, so this bounds how many distinct event names a single batch can introduce, not how many events it may carry.

Authorizations

Section titled “ Authorizations ”

Request Body

Section titled “ Request Body ”

Batch of events to record.

object
events
required
Array<object>
nullable
object
type
required
string
Allowed values: Evaluation Impression Identify Custom
flagKey
required
string
nullable
userId
string
nullable
variation
string
nullable
timestamp
string format: date-time
metadata
object
key
additional properties
prerequisiteKey
string
nullable

Responses

Section titled “ Responses ”

202

Section titled “ 202 ”

Events were accepted for processing.

400

Section titled “ 400 ”

The batch exceeds the maximum number of events per request.

Media type application/json
object
type
string
nullable
title
string
nullable
status
integer format: int32
nullable
detail
string
nullable
instance
string
nullable
key
additional properties
Example generated 
{
  "type": "example",
  "title": "example",
  "status": 1,
  "detail": "example",
  "instance": "example"
}

401

Section titled “ 401 ”

Client SDK key is missing or invalid.

Media type application/json
object
type
string
nullable
title
string
nullable
status
integer format: int32
nullable
detail
string
nullable
instance
string
nullable
key
additional properties
Example generated 
{
  "type": "example",
  "title": "example",
  "status": 1,
  "detail": "example",
  "instance": "example"
}

413

Section titled “ 413 ”

The request body is larger than this endpoint accepts.

Media type application/json
object
type
string
nullable
title
string
nullable
status
integer format: int32
nullable
detail
string
nullable
instance
string
nullable
key
additional properties
Example generated 
{
  "type": "example",
  "title": "example",
  "status": 1,
  "detail": "example",
  "instance": "example"
}