OptanonConsent — OneTrust
By the OpenCookies team · published 2026-10-22 · updated 2026-10-22
- Service
- OneTrust
- Category
- Strictly necessary
- Default duration
- 1 year
- Type
- First-party cookie (set by your own site)
- Consent required?
- No: a cookie strictly necessary for the requested service does not require consent.
What is it for?
Records the cookie choices made in the OneTrust banner (accepted categories, date, version), so the visitor is not asked again and the choice can be proven.
What does it look like?
The value is a parameter string: date, version, accepted categories (C0001:1,C0002:0…).
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 OptanonConsent cookie appears in the list if present, with its value and expiry date.
What does the rule say?
A cookie strictly necessary for the requested service does not require consent. It should still be listed in your cookie policy.
How to prevent it before the choice
Nothing to block: this is the cookie that stores the choice itself.
How OpenCookies handles it
OpenCookies does not block this cookie: it is needed for operation. The test still lets you see which cookies are set before any choice.
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
euconsent-v2— IAB TCF (plateformes de consentement)SOCS— Google
Frequently asked questions
What do C0001, C0002… mean?
They are OneTrust categories: C0001 strictly necessary cookies, the next ones analytics, functional and advertising, depending on configuration.
Does OneTrust really block trackers?
It depends on configuration: a browser test verifies it.
Durations are defaults and may change with configuration. This page describes a cookie; it is not legal advice.