User properties

User properties enable you to capture, manage, and analyze specific data about a user. You can use them to create filters or cohorts, which can then be used in insights, feature flags, and more.

How to set user properties

The recommended way to set user properties is to include them when capturing an event:

posthog.capture(
    'event_name', 
    { 
        $set: { name: 'Max Hedgehog'  },
        $set_once: { initial_url: '/blog' },
    }
)

You can also set user properties when you call the identify method:

posthog.identify(
  'distinct_id',  // Replace 'distinct_id' with your user's unique identifier
  { email: 'max@hedgehogmail.com', name: 'Max Hedgehog' } // optional: set additional user properties
);

User property values can be strings, booleans, numbers, objects, or arrays. For objects and arrays, you can use HogQL to access nested properties in the PostHog app.

Note that user properties are set in the order the events are ingested, and not according to event timestamps. Since we typically ingest events as soon as we receive them, you only need to take this into consideration when you're importing historical data.

What is the difference between set and set_once?

When using set, it will replace any value that may have been set on a person for a specific property. In contrast, set_once will only set the property if it has never been set before.

set is typically used for properties that may change over time – e.g., email, current plan, organization name. set_once is typically only used for information that is guaranteed to never change – e.g., the first URL a user visited, or the date a user first logged in.

For example:

posthog.capture(
    'event_name', 
    { 
        $set: { name: 'Max Hedgehog'  },
        $set_once: { initial_url: '/blog' },
    }
)
posthog.capture(
    'event_name', 
    { 
        $set: { name: 'Mr. Fox'  },
        $set_once: { initial_url: '/pricing' },
    }
)
// name: 'Mr. Fox'
// initial_url: '/blog'

How to remove user properties

Similarly to how you set properties, you can use $unset to remove properties with any event and including an array of properties keys:

posthog.capture(
    'event_name', 
    { 
        $unset: ['email'],
    }
)

How to view user properties

To view properties for a particular user, go to Persons & Groups in the PostHog app. Then, click on any person in the list to view their properties.

On a user's property list, you can add properties to them by clicking the "New property" button, then adding a key, type, and value. You can also delete a custom property for a user by clicking the red garbage bin icon on the right side of property listing.

Person display name

The person display name is the name that is shown in the PostHog UI. The person properties that are used as the display name can be configured in Project Settings.

Default user properties

The following properties are automatically set for all users when using the posthog-js library or JavaScript snippet:

GeoIP Properties

By default, the GeoIP plugin is turned on for all PostHog projects. This adds the following properties to all events.