Create flag variables

3 min

See Create flag variablesCreate flag variables in the user documentation to see the available variable types, detailed examples, and step-by-step instructions for creating variables using the Feature Experimentation UI.

For a specific use-case example using an image carousel iOS, see Flag variable example with an image carouselFlag variable example with an image carousel.

Create flag variable

Use the Feature Experimentation REST API

Use the Create Variable DefinitionCreate Variable Definition endpoint.

Endpoint – POST https://api.optimizely.com/flags/v1/projects/PROJECT_ID/flags/FLAG_KEY/variable_definitions

Authentication – Include your API key in the Authorization header as a Bearer token. See Generate tokens and use the REST APIsGenerate tokens and use the REST APIs.

Request example

curl --request POST \
     --url https://api.optimizely.com/flags/v1/projects/PROJECT_ID/flags/FLAG_KEY/variable_definitions \
     --header 'accept: application/json' \
     --header 'authorization: Bearer TOKEN' \
     --header 'content-type: application/json' \
     --data '
{
  "type": "TYPE",
  "default_value": "DEFAULT_VALUE",
  "description": "VARIABLE_DESCRIPTION",
  "key": "VARIABLE_KEY"
}
'

Response example

{
  "key": "show_amounts",
  "description": "If inventory is shown, this variable controls what is displayed: available/unavailable vs the actual inventory amount.",
  "type": "boolean",
  "default_value": "false",
  "created_time": "2025-09-12T16:23:14.258485Z",
  "updated_time": "2025-09-12T16:23:14.258487Z",
  "role": "admin"
}

See the Create Variable DefinitionCreate Variable Definition endpoint reference for the full list of parameters. You can also follow the REST API cookbookREST API cookbook and see step three to create eventsstep three to create events.

Use the Feature Experimentation UI

See Create flag variablesCreate flag variables in the user documentation.

Implement variables

After you have created your variables, the next step is to create flag variationscreate flag variations. Variations let you avoid hard-coding variables in your application and let you group and reuse variable values using flag rules.