What is the amplitude_id_ cookie?
amplitude_id_ belongs to the family of cookies set by Amplitude, a US-based product analytics platform used by companies to understand how users interact with a website or app. The full cookie name continues with an identifier (usually the project's API key), so each site using Amplitude has its own version of this cookie.
The cookie is created by Amplitude's Browser SDK, JavaScript code running directly on the page, which is why it appears as a first-party cookie set on the visited site's own domain rather than an Amplitude domain. It is typically set as soon as the tracking script loads and starts identifying the visitor, before any explicit user action.
What data it stores
The cookie mainly stores a unique, randomly generated device ID used to link together the events sent by the same visitor over time. Depending on how the SDK is configured, the value may also include additional information such as a session identifier or timestamps related to recently sent events. The exact value format can vary between SDK versions and is not publicly standardized.
Data tied to this identifier — pages viewed, actions taken, custom events — is sent from the site to Amplitude's servers for processing and display in analytics reports.
What it is used for
The cookie serves a purely analytical purpose: it lets Amplitude, on behalf of the site owner, recognize the same visitor across repeat visits and reconstruct their behavior, such as pages viewed, buttons clicked, or where they dropped off in a flow. This data feeds usage reports, conversion funnels, retention analysis, and user segmentation, which product and marketing teams use to inform decisions about features and campaigns.
Does it require consent?
amplitude_id_ is classified as a statistics (analytics) cookie and is not strictly necessary for the site to function. Under the GDPR and the ePrivacy Directive (implemented in Romania through Law 506/2004), setting it requires the visitor's prior, explicit consent, obtained before the Amplitude script runs.
- The site owner must disclose this cookie in the cookie policy, including its purpose and duration.
- The Amplitude script should be blocked by default until consent for the statistics category is given.
- Consent must be as easy to withdraw as it was to give.
How to block or delete amplitude_id_
A visitor can delete or block this cookie through their browser's privacy settings (Chrome, Firefox, Safari, Edge, etc.), either by clearing existing cookies for the site or by enabling third-party cookie blocking or private browsing. Since it is a first-party cookie, selectively blocking only this one without a dedicated tracking-blocker extension can be difficult.
For site owners, the correct approach is to block the Amplitude script from loading until consent is obtained, using a Consent Management Platform such as CookieFix, which prevents statistics-category scripts from running before the visitor makes a choice.
Frequently asked questions
Yes, it is used to analyze user behavior rather than for a site's core technical functions, which is why it's classified as a statistics cookie.
Amplitude uses a long expiration so it can recognize the same device over an extended period, which supports long-term retention and behavior analysis.
Yes. As a statistics cookie that isn't strictly necessary, it requires the visitor's prior consent under the GDPR and Romania's ePrivacy legislation.
You can clear cookies for the site in your browser settings or use private browsing; the script will recreate the cookie on a later visit if it runs again.