Bot filtering allows you to filter events by sending user agents to Optimizely with your events. Optimizely will compare the list of user agents you send to a list of known bots, and filter all user agents that are on the IAB/ABC blacklist.

## Enable bot filtering

Navigate to _Settings_ > _Advanced_ > _Bot Filtering_ in the Optimizely app to turn bot filtering on or off. For more information, see our KB article [Bot and spider filtering in Optimizely](🔗).

## Client-side JavaScript events

No additional JavaScript code is required to enable bot filtering for events sent from browsers. When you track an event by calling the JavaScript SDK’s [Activate](🔗), [Is Feature Enabled](🔗), or [Track](🔗) methods, the SDK automatically includes the user’s user agent in the outbound request. If bot filtering is enabled for your project, Optimizely applies bot filtering automatically.

## All other Full Stack events

When you track events with an SDK from somewhere other than a web browser, you must pass the user agent to be filtered with your event. You should pass it using the reserved `$opt_user_agent` attribute in the [Track](🔗), [Activate](🔗), [Is Feature Enabled](🔗), and [Get Enabled Features](🔗) functions. If bot filtering is enabled for your project and the user agent is passed in this way, Optimizely applies bot filtering.

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Note

**Enable bot filtering in Optimizely first**. Before implementing the `$opt_user_agent` attribute, navigate to _Settings_ > _Advanced_ in the Optimizely app to turn bot filtering on or off.

The example below shows how to pass the `$opt_user_agent` attribute.