_pk_id — Matomo
By the OpenCookies team · published 2026-10-22 · updated 2026-10-22
- Service
- Matomo
- Category
- Analytics
- Default duration
- 13 months
- Type
- First-party cookie (set by your own site)
- Consent required?
- Yes, in principle: only audience measurement meeting strict conditions can be exempt from consent in the EU.
What is it for?
Identifies a visitor for Matomo. Matomo can be configured to work without consent (under CNIL conditions); in a standard setup, this cookie requires consent.
What does it look like?
The name actually contains the site ID and a code (for example _pk_id.1.a1b2). The value combines the visitor ID and dates.
How to see it in your browser
Open your site, press F12, then choose the “Application” tab (Chrome, Edge) or “Storage” (Firefox). Under “Cookies”, select your site’s address: the _pk_id cookie appears in the list if present, with its value and expiry date.
What does the rule say?
Audience measurement in principle requires the visitor’s prior consent. The French CNIL accepts an exemption for some tools configured very strictly (statistical purpose only, no cross-referencing with other data and no cross-site tracking); detailed conditions are on its website.
How to prevent it before the choice
Either configure Matomo in exempt mode, or load it only after consent.
How OpenCookies handles it
Common services like this one are in OpenCookies’ tracker list: the banner neutralizes their script before the visitor chooses and only restarts it after “Accept”. The test shows whether this cookie appears before the choice, after “Refuse” and after “Accept”.
Check it on my site
Does this cookie appear on your site before the visitor chooses? The OpenCookies test shows it in two minutes.
Related cookies
Frequently asked questions
Can Matomo run without consent?
Under strict configuration conditions (statistical purpose only, no cross-referencing), the CNIL accepts an exemption for some tools. Check its dedicated page.
What is Matomo’s session cookie?
_pk_ses, which lasts 30 minutes.
Durations are defaults and may change with configuration. This page describes a cookie; it is not legal advice.