What is the _cb cookie?
_cb is a cookie set by Chartbeat, a US-based web analytics platform widely used by publishers and media sites to measure traffic, time on page, and reader engagement in real time.
The cookie usually appears when a site loads Chartbeat's tracking script on its pages. It is typically set as a first-party cookie by the visited site's domain (served through the Chartbeat script) or, depending on the implementation, by domains associated with Chartbeat.
What data it stores
_cb stores a unique, randomly generated identifier used to distinguish one visitor from another within Chartbeat's analytics tools. The exact value format is not documented in public detail and may vary.
The data collected through this cookie is sent to Chartbeat's servers for processing and aggregation into audience reports; it is not displayed directly to the visitor.
What it is used for
The main purpose of _cb is statistical: it lets Chartbeat recognize returning visitors and build metrics such as active user counts, average time on page, and navigation paths across a site.
For site owners, this data helps understand reader behavior, optimize content, and make editorial decisions based on actual audience engagement, rather than for targeted advertising.
Does it require consent?
In CookieFix's classification, _cb falls under the statistics (analytics) category. Under GDPR and the ePrivacy Directive (transposed in Romania via Law 506/2004), this type of cookie is not strictly necessary for the website to function, so it requires the visitor's prior consent before being set.
Site owners must list the cookie in their cookie policy, place it correctly under the statistics category in the consent banner, and make sure the Chartbeat script does not load before the visitor gives consent.
How to block or delete _cb
Visitors can delete or block _cb through their browser settings (managing cookies per site or clearing browsing data), as well as by enabling options that block third-party or tracking cookies.
- Browser privacy settings (Chrome, Firefox, Safari, Edge) allow deleting existing cookies for a given domain.
- Anti-tracking browser extensions can prevent this cookie from being set on future visits.
- Site owners can use a CMP such as CookieFix, which automatically blocks the Chartbeat script until the visitor consents to the statistics category, preventing the _cb cookie from being set prematurely.
Frequently asked questions
No, it's an analytics cookie used for traffic statistics; it does not contain sensitive data and is not used for targeted advertising.
It typically lasts around 13 months, after which it expires automatically if the visitor does not return to the site.
Yes, as a statistics cookie it requires the visitor's prior consent under GDPR and ePrivacy, except in rare cases of strictly aggregated, anonymized measurement.
The site works normally, but Chartbeat won't be able to accurately measure your visit in the publisher's audience reports.