Overview
Webtrends Optimize uses cookies to personalize your experience and ensure accurate running of your experiences. Below is an easy-to-understand overview of each cookie, followed by more advanced technical details for those who need them.
1. User Cookie
Overview:
This cookie identifies you as a unique visitor and helps keep track of your session while you're on the site. It ensures consistency so that you don’t see different versions of a page during your visit and allows site owners to measure user interactions accurately.
Advanced:
Example:
_wt.user-1908787Data stored:
Unique user identifier
Anonymous Session ID
Session start time (timestamp)
The value of this cookie is encrypted, and so if viewed in its raw format you'll see something like:
WT3zLURvgbOrd9DBJOrWqfSuHMNS0nfKISNIiNJzpq1d-_F468574DrkSdTSlToHoBjA7lbpgxIqVPJAg3Da89mGMwFgps301xlO39V3LQkps6WJgpoXNrKUhWZsoLoUNpa2Td8QJVEVBfLMklReAz-GmXLwjBN5iwv_NTPlAFFARQP3X8214ra91Nx5aiThNfRDyM894L2i1c~
2. Mode Cookie
Overview:
This cookie determines whether you’re seeing the live website (normal mode) or a testing version (staging mode). It's mostly used by developers and testers to preview changes before going live.
Advanced:
Example:
_wt.mode-1908787Possible values:
normalorstaging
The value of this cookie is encrypted, and so if viewed in its raw format you'll see something like:
WT3RzAoZZKALKg~
3. Project Cookie
Overview:
Used during experiments like A/B testing, this cookie stores which version of a page or feature you were shown. It ensures that you see the same version consistently and helps measure which version performs better.
Be aware - settings in your tag allow this to be kept in local storage instead of as a cookie when using tag version 5.8 and above. For more info on tag versions please see this article.
Advanced:
Example:
_wt.project-1908787-ta_WelcomeVideoData stored:
Type of experiment (e.g. AB test)
Experiment alias
Page view recorded (true/false)
Group assigned in the experiment/throttle
The value of this cookie will appear similar to:
1||88067-88074-88077||true||IN
4. Control Cookie
Please note this has been superseded by the project cookie as shown above
Overview:
This older cookie worked like the Project Cookie to track experiment participation but has since been replaced by a more efficient version. You may still see it on sites using older configurations.
Advanced:
Example:
_wt.control-1908787-ta_WelcomeVideoStructure: Same as Project Cookie
5. JSESSIONID Cookie
Please note the presence of this cookie is not essential to the running of Webtrends Optimize, and as such it will be written-out of the platform in the V6 tag, due to be released in late 2024.
Overview:
This cookie is used by the backend system to manage your session while content is being delivered to you. It helps maintain a stable connection with the server, especially when Webtrends Optimize serves content like scripts or assets.
Advanced:
Set on:
.webtrends-optimize.appCreated by: The Webtrends Optimize Content Delivery System (CDS)
6. Tests History Cookie
Overview:
This cookie keeps a record of the experiments you've already participated in. It helps prevent you from being added to the same test again and supports consistent reporting for experiment results.
Advanced:
Example:
_wt.testsHistoryValue: A comma-separated list of experiment aliases (e.g.
ta_WelcomeVideo,ta_GuidedTour)
Other cookies you may come across
For the majority of users, the above cookies are the only ones they will come across however Webtrends Optimise does use extra cookies when using the New vs. Returning visitor capability.
Want to find more info on New vs. Returning user capability? See this article.
Tracking a User’s Visit (Session Management)
When someone visits your site, WTO uses a cookie called _wt.sm to track their current session (how long they stay on the site).
This cookie tracks the user while they’re actively browsing.
It expires after 30 minutes of inactivity — so if someone stops clicking around for half an hour, WTO considers their visit “finished”.
Counting How Many Times Someone Has Visited
If a user doesn’t already have a session cookie, WTO assumes it’s a new visit. It then updates another cookie called _wt.sc, which counts how many separate times that person has been to your site.
So:
The first time someone visits,
sc = 1On their second or third visit, it increases to
sc = 2,sc = 3, and so on
Identifying First-Time vs. Returning Visitors
WTO uses that session count cookie (_wt.sc) to figure out what kind of visitor someone is:
If the session count is 1, they’re a first-time visitor
If it’s more than 1, they’re a returning visitor
This helps you:
Run A/B tests that behave differently for new vs. returning users
Personalize content based on visit history
In Summary:
Cookie | What it does | Why it matters |
| Tracks the current visit | Helps know how long a user stays active |
| Counts total visits | Lets WTO tell if a user is new or returning |
Cookie Duration and Scope
By default, cookies from Webtrends Optimize last for 90 days and are set for the website’s domain. However, both the duration and domain can be customized to suit specific needs like privacy or subdomain tracking.
Cookie timeout/duration
This is configured as part of your tag configuration which can be found by accessing the tag configuration screen and choosing to edit your tag.
In here you have the ability to set the cookie timeout which is based in milliseconds.
Cookie scope
Although test delivery is controlled by locations, more info here, domains will default to the sub-domain set as part of the location.
This can be overwritten and is controlled globally. To achieve this, navigate to tag configuration (as above) and select 'myPreInitScript':
Add this variable into the preinit section of the tag configuration, replacing 'app.mysite.com' with the domain you wish to set:
WT.optimizeModule.prototype.wtConfigObj.cookieDomain = "app.mysite.com";
Save this configuration and the new cookie domain will be set.
Removing Cookies
In some cases—like testing, debugging, or resetting user data—you may want to delete Webtrends Optimize cookies. This can be done manually through browser tools or by running a small piece of JavaScript.
Deleting cookies - via your tag manager
The wt.js tag has a 24hr cache, and so we recommend using your tag manager to do this effectively.
We recommend:
Removing the wt.js tag from your website, or use the killswitch in Optimize to stop experiment delivery.
Run this code on your machine, when you have cookies, to ensure they get deleted. Cookies are variable in how they're created, and this does not always work.
Confirming above, paste this code into your tag manager for immediate deployment .
document.cookie.match(/_wt.[^=]+/g).forEach(name => {
if(WT.optimizeModule.prototype.wtConfigObj.cookieDomain)
WT.helpers.cookie.set(name, "", -1, "/", WT.optimizeModule.prototype.wtConfigObj.cookieDomain || document.domain);
else
WT.helpers.cookie.del(name);
});Deleting cookies - alternative method
An alternative method to do this is to build a sitewide target. This would require using the 'Create' form and selecting target whilst creating a location that encompasses the entire site.
More information on creating a target can be found here.
More information on creating a sitewide location can be found here.
Use the following code as your target:
var clearwtocookies = setInterval(function(){
document.cookie.match(/_wt.[^=]+/g).forEach(name => {
if(WT.optimizeModule.prototype.wtConfigObj.cookieDomain)
WT.helpers.cookie.set(name, "", -1, "/", WT.optimizeModule.prototype.wtConfigObj.cookieDomain || document.domain);
else
WT.helpers.cookie.del(name);
});
}, 2000);Things to note when using this method:
Cookies can be created post-pageload and the target would create cookies too, we would suggest running this on a setInterval.
This will run endlessly, but is a fairly light check and 2s is not too frequent to degrade user experience.
As with the tag manager method above, you should make sure this works on your machine before deploying it to others, to ensure it solves the problem.
Cookie inspection
What is Cookie Inspection?
In Webtrends Optimize, cookie inspection is an optional setting that affects how cookies are handled when a user visits your site and interacts with a test.
Normally, WTO sets cookies to:
Track which variation a user saw
Log conversions (like purchases or signups)
Manage session and user identity
Prevent duplicate tracking of the same conversion event
What Happens When Cookie Inspection is On?
When this setting is enabled:
Some non-essential WTO cookies are not sent on the page
This is often done to comply with stricter privacy or cookie policies
As a result, WTO might not realize it already tracked a user’s conversion
This can lead to:
Duplicate metric tracking — the same user action might be logged more than once, because WTO doesn’t have the cookie data to know it already tracked it.
This is usually prevented by default, but with cookie inspection on, that safeguard is reduced.
When Does This Matter?
It mainly affects:
Page Load UI Conversions
These are basic UI-based conversions that fire when a user:
Lands on a thank-you page
Triggers a goal set in the visual editor (e.g. reaching
/checkout-complete)Clicks a tracked element on the page
Because these rely on what’s visible in the browser, they often use cookies to check whether they’ve already fired for a user.
Not affected: Conversion Package goals
Conversion packages (custom JS-based events or API calls) don't rely on cookies in the same way. They send data explicitly and bypass cookie inspection issues.
Why Enable Cookie Inspection?
It can be helpful when:
Your site is rejecting cookies due to cookie consent tools
You're using WTO in strict privacy environments
You want less cookie reliance, but can accept duplicate tracking
Summary
Feature | With Cookie Inspection OFF | With Cookie Inspection ON |
WTO sets all cookies | Yes | Some blocked |
Duplicate conversions prevented | Yes | May happen |
Page Load UI Goals | Work reliably | May double track |
Conversion Package Goals | Work the same | Work the same |
Should you use it?
Don't enable cookie inspection unless you have a specific privacy or technical reason.
Leave it off for normal A/B testing to ensure accurate conversion tracking.