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List of cookies we use

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First party cookies

List of cookies created by IET web domains


When you are not logged in, most IET sites use cookies to manage your session. You may block these if you wish, but some functions may not work fully; for example, you will not be able to page through results in the events calendar. The IET does not use these cookies to monitor your behaviour; they exist only to provide you with site functionality. The book shop also uses your existing site cookies to keep track of the contents of your shopping basket, rather than setting additional ones. Without accepting cookies, you will not be able to use the shop.

Cookie set by Adobe ColdFusion applications. Used in conjunction with CFTOKEN this cookie helps to uniquely identify a client device (browser) to enable the site to maintain user session variables. How those are used are specific to the site. CFID contains a sequential number to identify the client. The main purpose of this cookie is: Strictly Necessary

Third party cookies

A third-party cookie is one that is placed on a user's hard disk by a Web site from a domain other than the one a user is visiting. 


Third party widget that presents a selection of social sharing links to users and also provides publishers with in-depth analytics


__atuvc stores an updated page share count

__atuvs displays counter to user if page is shared with the selected social-sharing service

b2 records visited pages in a site in order to recommend other pages in that site


loc Geolocation, which is used to help providers determine how users who share information with each other are geographically located (state level).




uvc Records how often AddThis encounters the same user IP address

Google Analytics

Third party web analytics service


__utma records whether the visitor came from a search engine (and if so, the search keyword used), a link, or from no previous page (e.g. a bookmark).

















Olark live chat software

Instant message web communication


_ok  contains a site identifier, used for security purposes

_okbk contains software state information


_oklv  used to improve caching of software


_pinterest_cm - Enables users to follow the IET 'pinboard' 


We use Siteimprove cookies to help us identify content presentation issues such as broken links and prioritise remedial action where there may be multiple instances to correct.


__cfduid  - records and relays back a count of clicks on broken links


We use Hotjar to collect both analytics and feedback directly from our members via the website. This gives us the insight needed to improve the overall experience for our users.

Hotjar is not designed to track individual users, however, you can tell Hotjar not to collect your data.


_hjClosedSurveyInvites - set once a user interacts with an External Link Survey invitation modal. It is used to ensure that the same invite does not reappear if it has already been shown.

_hjDonePolls - set once a user completes a survey using the On-site Survey widget. It is used to ensure that the same survey does not reappear if it has already been filled in.

_hjMinimizedPolls - is set once a user minimizes an On-site Survey widget. It is used to ensure that the widget stays minimized when the user navigates through your site.

_hjShownFeedbackMessage - set when a user minimizes or completes Incoming Feedback. This is done so that the Incoming Feedback will load as minimized immediately if the user navigates to another page where it is set to show.

_hjSessionTooLarge - causes Hotjar to stop collecting data if a session becomes too large. This is determined automatically by a signal from the WebSocket server if the session size exceeds the limit.

_hjSessionRejected - If present, this cookie will be set to '1' for the duration of a user's session, if Hotjar rejected the session from connecting to our WebSocket due to server overload. This cookie is only applied in extremely rare situations to prevent severe performance issues.

_hjSessionResumed - A cookie that is set when a session/recording is reconnected to Hotjar servers after a break in connection.

_hjid - set when the customer first lands on a page with the Hotjar script. It is used to persist the Hotjar User ID, unique to that site on the browser. This ensures that behaviour in subsequent visits to the same site will be attributed to the same user ID.

_hjRecordingLastActivity - this should be found in Session storage (as opposed to cookies). This gets updated when a user recording starts and when data is sent through the WebSocket (the user performs an action that Hotjar records).

_hjTLDTest - when the Hotjar script executes we try to determine the most generic cookie path we should use, instead of the page hostname. This is done so that cookies can be shared across subdomains (where applicable). To determine this, we try to store the _hjTLDTest cookie for different URL substring alternatives until it fails. After this check, the cookie is removed.

_hjUserAttributesHash - user Attributes sent through the Hotjar Identify API are cached for the duration of the session in order to know when an attribute has changed and needs to be updated.

_hjCachedUserAttributes - this cookie stores User Attributes which are sent through the Hotjar Identify API, whenever the user is not in the sample. Collected attributes will only be saved to Hotjar servers if the user interacts with a Hotjar Feedback tool, but the cookie will be used regardless of whether a Feedback tool is present.

_hjLocalStorageTest - this cookie is used to check if the Hotjar Tracking Script can use local storage. If it can, a value of 1 is set in this cookie. The data stored in_hjLocalStorageTest has no expiration time, but it is deleted almost immediately after it is created.

_hjIncludedInPageviewSample -  this cookie is set to let Hotjar know whether that user is included in the data sampling defined by your site's pageview limit.

_hjIncludedInSessionSample - this cookie is set to let Hotjar know whether that user is included in the data sampling defined by your site's daily session limit.

_hjAbsoluteSessionInProgress - this cookie is used to detect the first pageview session of a user. This is a True/False flag set by the cookie.

_hjFirstSeen - this is set to identify a new user’s first session. It stores a true/false value, indicating whether this was the first time Hotjar saw this user. It is used by Recording filters to identify new user sessions.

_hjViewportId - this stores information about the user viewport such as size and dimensions.

_hjRecordingEnabled - this is added when a Recording starts and is read when the recording module is initialized to see if the user is already in a recording in a particular session.