piwik.js: Cross domain tracking

[anonymous-matomo-user]

(ticket description updated by @mattab)

The goal of this ticket is to be able to measure a unique user across several domain names, by having Piwik.js automatically forwarding the User ID for this user in the URL as a query parameter.

Details

First party cookie by design will be only created and available in this domain where they were created. To allow for accurate cross-domains reporting, we need a way to persist the UUID (unique identifier) in the first party cookie from one domain to another domain.

The solution is to implement a mechanism that automatically decorates DOM elements within the page, which are links, and will add a GET Parameter to links, with the User ID.

Note: this feature has been available in Google universal analytics forever, and is well documented here: Universal analytics cross domain tracking. (this is a must read!)

Maybe in Piwik we can support the following methods:

• 'Decorate Utility Method'
• 'Decorating HTML Links'
• 'Cross Domain Auto Linking'
• Linker parameters are only valid for 2 minutes after they are created. Avoids user being assigned to wrong user id when sharing URLs with others.

Notes

• we probably should implement User ID Accurate User Detection cross devices: User ID (set in JS and all other clients) #3490 first
• tracking unique users across websites will only accurately track users that clicked from one website to another. If user visits both websites independently, he will be assigned two different User IDs.
• Will not be done in MVP:
  • Tracking Across iFrames
  • Decorating HTML Forms

[robocoder]

Cross-domain linking works by the referring site adding parameters to the URL which the receiving site parses. (It's a little trickier with form submissions, but also doable.)

The main limitation is that first party cookies cannot be shared across different top level domains, i.e., x.com and y.com.

If we implement this feature, I propose:

• site would use setDomains('y.com')
• copy the idsite, uuid (from the visitor cookie), referring URL and timestamp (from the referral conversion cookie), and (maybe) custom variables
• setAllowLinker(true) (or perhaps a more obvious name to enable this feature, so as to not confuse with enableLinkTracking)

[robocoder]

Maybe: tracker.enableCrossDomainLinker( boolCopyCookies );

[mattab]

tracker.enableCrossDomainsLinker (with a "s") maybe?

was your idea to pass the parameters, automatically on all clicks to domains that were specified in setDomains('y.com') ?

I think it's a must have indeed (especially with Ecommerce sites).

[robocoder]

I envision it being automatic.

[mattab]

Notes
In GA it used to be done with:

_gaq.push(['_setDomainName', 'none']);
_gaq.push(['_setAllowLinker', true]);

Update 2014: In Universal analytics it is done this way:

ga('require', 'linker'); // Load the plugin.

// Define which domains to autoLink.
ga(linker:autoLink, [3-party.com, 3-party-domain.com]); //add as many as you need third party sites

on third party domain add

ga(create, 'UA-XXXXXX-X', { allowLinker: true });

See also this forum post

[asafyish]

+1

[pirate]

+1

[asafyish]

I think we can partially accomplish it by exposing a setVisitorId method on the JS tracker, it will still require manual work for reading, and transferring the visitor id between domains, but it's still better then the current situation.

[pirate]

Yes, I believe that's already done and the docs are here: http://piwik.org/docs/user-id/
What I'm hoping for is a native baked-in solution that generates a unique ID and appends it to all the links that go to alias domains on the page, so that we can consistently track the same user across multiple domains (not just subdomains).

[cemdev]

+100

[mattab]

PR: #11243

[mattab]

Cross domain tracking is available in Piwik 3.0.2-b1 release.

To use it configure it as follows in the Piwik Tracker code:

_paq.push(['setDomains', ['domain-1.net', 'domain-2.net']]);
_paq.push(['enableCrossDomainLinking']);
_paq.push(['setSiteId', X]);

(when adding both these lines in domain-1.net and domain-2.net -> users clicking from either website to the other website, will be automatically recognised as the same visitor and tracked in the same visit in website id X)

[mattab]

Before closing the issue:

• Document cross domain feature in the JavaScript tracking guide
• Add new FAQ
• Create a separate issue for backend improvement: ensure that Visitor ID is the same across all visits of a given visitor and re-uses the last visitor id value set or similar

[tsteur]

when adding both these lines in domain-1.net and domain-2.net

We need to clearly mention it needs to be enabled on all domains / websites

backend improvement: ensure that Visitor ID is the same across all visits of a given visitor and re-uses the last visitor id value set

We should do it actually as part of this issue, it is in most cases not working without it.

[mattab]

Note: Cross Domain feature is also useful when the data is tracked into different websites in Piwik. In that case, there won't be just "one visit" created, but "one visit per website". The advantage of using cross domains is that those two visits across website IDs will have the same Visitor ID. Could be super useful and we need to mention it in docs 👍

[mattab]

Important:

• Need to add a new checkbox in JavaScript Tracker Code screen, to let users enable cross domain tracking which will 1) enable the setDomains existing checkbox automatically and 2) output in the code the _paq.push(['enableCrossDomainLinking']);

[mattab]

• Created new FAQ: How do I accurately measure a same visitor across multiple domain names (cross domain linking)?
• Added link into related faqs https://piwik.org/faq/new-to-piwik/faq_104/ and into manage websites user guide
• and developer guide https://github.com/piwik/developer-documentation/pull/175/files for JS Tracker code guide