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Anonymous tracking

Anonymous tracking is a tracker feature that enables anonymizing various user and session identifiers to support user privacy in case consent for tracking the identifiers is not given.

On mobile, the following user and session identifiers can be anonymized:

  • Client-side user identifiers:
    • userId in the Session context entity
    • IDFA identifiers (appleIdfa and appleIdfv for iOS, androidIdfa for Android) in the Platform context entity
    • userId, domainUserId, networkUserId, ipAddress if they are set in Subject
  • Client-side session identifiers: sessionId and previousSessionId in Session entity.
  • Server-side user identifiers: network_userid and user_ipaddress event properties.

On web, the following identifiers can be anonymised:

  • Web client-side user identifiers: domain_userid in the event, also present as userId in the Session context entity.
  • Web client-side session identifiers: domain_sessionid and domain_sessionidx in the event, which are also present in the Session entity as sessionId, and sessionIndex.
  • Server-side identifiers: network_userid and user_ipaddress event properties.

There are several levels to the anonymisation depending on which of the three categories are affected:

1. Full client-side anonymisation​

In this case, we want to anonymise both the client-side user identifiers as well as the client-side session identifiers. Here the Session entity is not configured: no session information will be tracked at all.

const TrackerConfiguration()
    .userAnonymisation(true)
    .sessionContext(false)
    .platformContext(true) // only relevant for mobile

On web, setting userAnonymisation stops any user identifiers or session information being stored in cookies or localStorage. This means that domain_userid, domain_sessionid, and domain_sessionidx will be anonymised. These properties are already not present in any mobile events.

On mobile, setting userAnonymisation affects properties in the Session and Platform entities. In this example, the Platform entity is enabled. The appleIdfv Platform property would be anonymised, as well as appleIdfa/androidIdfa if your app is configured to track those.

2. Client-side anonymisation with session tracking​

This setting disables client-side user identifiers but tracks session information.

const TrackerConfiguration()
    .userAnonymisation(true)
    .sessionContext(true)
    .platformContext(true) // only relevant for mobile

Enabling both userAnonymisation and sessionContext means that events will have the Session context entity, but the userId property will be anonymised to a null UUID (00000000-0000-0000-0000-000000000000). The sessionId and sessionIndex are still present, as are domain_sessionid and domain_sessionidx for web events. As above, if the Platform context entity is enabled, the IDFA identifiers will not be present.

3. Server-side anonymisation​

Server-side anonymisation affects user identifiers set server-side. In particular, these are the network_userid property set in server-side cookie and the user IP address (user_ipaddress). You can anonymise the properties using the serverAnonymisation flag in EmitterConfiguration:

const EmitterConfiguration()
    .serverAnonymisation(true)

Setting this will add a SP-Anonymous HTTP header to requests sent to the Snowplow collector. The Snowplow pipeline will take care of anonymising the identifiers.

On mobile, serverAnonymisation and userAnonymisation are separate. This means you can anonymise only the server-side identifiers without also anonymising the client-side identifiers.

On web, serverAnonymisation is effectively a subset of userAnonymisation. If serverAnonymisation is enabled, this will also set userAnonymisation to true (even if set to false in your TrackerConfiguration).