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Snowplow JavaScript Tracker 2.4.0 released

We are pleased to announce the release of version 2.4.0 of the Snowplow JavaScript Tracker! This release adds support for cross-domain tracking and a new method to track timing events.

Read on for more information:

  1. Tracking users cross-domain
  2. Tracking timings
  3. Dynamic handling of single-page apps
  4. Improved PerformanceTiming context
  5. Other improvements
  6. Upgrading
  7. Documentation and help

1. Tracking users cross-domain

Version 2.4.0 of the JavaScript Tracker adds support for tracking users cross-domain. When a user clicks on one of the links you have specified (or navigates to that link using the keyboard), the Tracker adds the user’s domain user ID together with a timestamp for the click to the querystring of that link in an “_sp=…” querystring field. If the JavaScript Tracker is also present on the destination page, it will send the URL of the page – including the new querystring field – with all events.

Snowplow r63 (coming soon), will add new refr_domain_userid and refr_dvce_tstamp fields to the atomic.events table, which will then be populated based on the “_sp” field.

You can control which links should be decorated using a filter function. For each link element on the page, the function will be called with that link as its argument. If the function returns true, event listeners will be added to the link and will decorate it when the user navigates to it.

To enable cross-domain tracking, add this function to the tracker constructor argmap with the key “crossDomainLinker”.

For example, this function would only decorate those links whose destination is “http://acme.de” or whose HTML id is “crossDomainLink”:

snowplow('newTracker', 'cf', 'd3rkrsqld9gmqf.cloudfront.net', { crossDomainLinker: function (linkElement) { return (linkElement.href === "http://acme.de" || linkElement.id === "crossDomainLink"<span class="p">); } <span class="p">});

If you want to decorate every link to the domain github.com:

snowplow('newTracker', 'cf', 'd3rkrsqld9gmqf.cloudfront.net', { crossDomainLinker: function (linkElement) { return /^https://github.com/.test(linkElement.href<span class="p">); } <span class="p">});

If you want to decorate every link, regardless of its destination:

snowplow('newTracker', 'cf', 'd3rkrsqld9gmqf.cloudfront.net', { crossDomainLinker: function (linkElement) { return true<span class="p">; } <span class="p">});

If new links are added to the page after the tracker is initialized, you can enable decoration for them using the crossDomainLinker tracker method:

snowplow('crossDomainLinker', function (linkElement) { return (linkElement.href === "http://acme.de" || linkElement.id === "crossDomainLink"<span class="p">); })

2. Tracking timings

The new trackTiming method can be used to track user timing information. This example uses the method to send a timing event describing how long it took a map to load:

snowplow( 'trackTiming', 'load', // Category of the timing variable 'map_loaded', // Variable being recorded 50, // Milliseconds taken 'Map
 loading time' // Optional label <span class="p">);

You can see the JSON schema for the event that the method generates here.

3. Dynamic handling of single-page apps

Previous versions of the JavaScript Tracker would retrieve the page’s URL and referrer’s URL on page load and never update them. This was problematic for single-page applications (SPAs), with Snowplow users resorting to manually setting a custom page/referrer URLs whenever the URL changed inside the SPA.

Version 2.4.0 of the Tracker automatically detects when the page URL changes and updates the page URL and referrer accordingly. The referrer is replaced by the old page URL. Note that you must send at least one event each time the URL changes, because the Tracker will not notice a skipped URL. This means that if the user navigates from page1 to page2 to page3, but no events are fired while on page3, the referrer reported for all events fired on page3 will stil be page1.

When you use the setCustomUrl, the page URL reported by the Tracker will “stick” at the supplied value until the JavaScript Tracker is reloaded – unless of course you call setCustomUrl again. Setting the referrer URL using setReferrerUrl is similarly sticky.

4. Improved PerformanceTiming context

We recently added the ability to add a context containing data from the Navigation Timing API to all events. At the time the context gets constructed, some of the timing metrics (typically loadEventEnd, loadEventStart, and domComplete) are usually not yet available.

With this releaes, the context is recalculated with every event instead of being cached, so missing timing metrics will be added to subsequent events as soon as those metrics become available.

5. Other improvements

We have also:

  • Started adding common contexts (including the PerformanceTiming context) to form_change, form_submit, and link_click events, the only event types to which they were not already automatically added if enabled #340
  • Increased the reliability of the JavaScript Tracker’s document size detection #334
  • Started randomly generating the ngrok subdomain used for our integration tests to prevent clashes when the tests are run more than once simultaneously #333
  • Updated the Vagrant setup to work with the latest version of Peru #336

6. Upgrading

The upgraded minified tracker is available here:


This release is fully backward-compatible.

7. Documentation and help

Check out the JavaScript Tracker’s documentation:

The v2.4.0 release page on GitHub has the full list of changes made in this version.

Finally, if you run into any issues or have any questions, please raise an issue or get in touch with us via the usual channels.

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