Gemius
Gemius is the leading Polish and Central European audience measurement and ad effectiveness platform. Operated by Gemius S.A. from Warsaw, it combines a JavaScript tag installed on publisher and advertiser websites with a recruited household panel to produce official audience numbers (Mediapanel in Poland, Audience in Romania and other CEE markets). Because Gemius sets third party cookies and joins panel and tag data, it is treated as a high risk advertising and audience tracker under the GDPR and ePrivacy Directive.
What does Gemius do?
What Gemius is
Gemius is the dominant audience and advertising measurement company in Poland and Central Europe, operated by Gemius S.A. from Warsaw. Major national publishers, broadcasters and advertisers participate in joint industry currencies (Mediapanel, PBI/Gemius, Atinternet/Gemius collaborations). The product combines a JavaScript tag deployed on participating sites with a recruited household panel to produce census + panel hybrid audience reports.
What data Gemius collects
The Gemius tag captures page views, time on page, the IP address, the user agent, the referrer and a persistent visitor identifier stored in third party cookies (Gtest, Gdyn variants). When a visitor is in the Gemius household panel, additional sociodemographic attributes are linked to the activity. The tag also exchanges signals with the IAB TCF (Gemius is a registered vendor) to forward consent state to downstream partners.
GDPR and ePrivacy implications
The Gemius cookies fall under Article 5(3) ePrivacy and require prior consent. The persistent visitor identifier and the panel join are personal data processing under Article 4(1) GDPR and require a clear legal basis. Polish UODO and other CEE regulators have repeatedly stated that legitimate interest cannot justify cross site advertising profiling.
Consent requirements
The Gemius tag must be tag blocked until explicit, granular opt in consent is granted. The CMP must forward the IAB TCF v2.2 string with the Gemius vendor ID. Visitors must be able to refuse with the same effort as accepting. The consent message should mention Gemius, the audience measurement purpose and the panel join.
International data transfers
Production data is processed in Poland and other EU member states. Gemius does not systematically transfer personal data to non EEA countries. Sub processors are publicly listed and can be reviewed by customers. The lower transfer risk is a meaningful advantage compared to US based tracking peers.
Practical compliance steps
Sign the Gemius DPA, configure the CMP IAB TCF v2.2 string with the Gemius vendor ID, document the joint controllership relationship with the audience measurement body when required (Mediapanel, PBI), list Gemius in the privacy and cookie policies, and review the configuration after each TCF or Gemius tag update.
Gemius and the GDPR
Gemius is classified as “Analytics”. On a site that targets European visitors, it must only load after the visitor consents, and it must be listed in your cookie policy.
- Legal basis
- Consent (Art. 6(1)(a) GDPR + Art. 5(3) ePrivacy Directive) for the cookies set by the Gemius script and for the joint audience measurement with the Gemius household panel. Legitimate interest is not admissible for the panel based profiling, even if Gemius is sometimes positioned as official audience measurement.
- Risk level
- high
- Applicable regulations
- GDPR, ePrivacy Directive, IAB TCF v2.2, Polish UODO guidelines, German TTDSG, Spanish LSSI, Italian Garante guidelines, French CNIL guidelines
Impact assessment (DPIA)
A DPIA is recommended for European deployments because Gemius combines client side tracking with a household panel, builds persistent visitor profiles, takes part in the IAB TCF chain and processes data at very large scale on behalf of national audience measurement bodies.
Sample text for your banner
We use Gemius (Gemius S.A., Poland) to measure audience and the effectiveness of advertising. Gemius sets cookies that link your activity to a panel based audience model. We only load Gemius after you click Accept. You can withdraw your consent at any time from the cookie settings.
What Gemius sets and contacts
- Tracking method
- JavaScript tag (gemius.js) loaded from gemius.pl, hit collection from publishers and advertiser sites, third party cookies (Gtest_*, Gdyn_*) for visitor identification, panel based audience measurement combining tag data with a recruited household panel, IAB TCF v2.2 vendor.
- Server location
- Gemius S.A. is headquartered in Warsaw. Production data centres are located in Poland and other EU member states. EU customer data is processed inside the EU.
Cookies set (3)
| Name | Type | Duration | Purpose |
|---|---|---|---|
| Gtest | persistent | 24 months | Persistent visitor identifier used by Gemius to link page views to a unique browser within the audience measurement census. |
| Gdyn | persistent | 13 months | Behavioural identifier used to enrich the visitor profile with site interaction signals for hybrid audience reports. |
| GtestExt | persistent | 24 months | Cross domain identifier shared between Gemius operated tracking endpoints to link activity across multiple publishers. |
Third-party domains contacted (4)
gemius.plhit.gemius.plgapt.hit.gemius.plgemius.com
Frequently asked questions about Gemius
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What cookies does Gemius set?
Gemius sets the third party cookies Gtest, Gdyn, GtestExt and a session cookie on its operator domains (gemius.pl, hit.gemius.pl). They persist for 13 to 24 months by default and are used to identify a unique browser, link visits to the household panel and forward signals through the IAB TCF.
Do I need consent to use Gemius?
Yes. The cookies fall under Article 5(3) ePrivacy and the audience profiling under Article 6(1)(a) GDPR. Gemius participates in the IAB TCF v2.2 chain, which means consent must be collected through your CMP and forwarded to Gemius via the TCF string.
What is the legal basis for Gemius?
Consent (Art. 6(1)(a) GDPR + Art. 5(3) ePrivacy). Legitimate interest is not admissible because the persistent identifier and the panel join build cross site profiles, even when the underlying purpose is industry audience measurement.
Does Gemius transfer data to the US?
No. Gemius S.A. processes data in the EU, primarily in Poland. There is no systematic transfer to non EEA countries. Sub processors are listed publicly. This makes Gemius a lower transfer risk option than US based audience peers.
Do I need a DPIA for Gemius?
Yes for any meaningful EU deployment. The combination of large scale cross site profiling, persistent identifiers, IAB TCF participation and joint controllership with national audience measurement bodies (Mediapanel, PBI) triggers the DPIA criteria of WP248 and the EDPB threshold guidance.
How do I implement Gemius compliantly?
Sign the Gemius DPA, configure the CMP IAB TCF v2.2 string with the Gemius vendor ID, document the joint controllership when participating in Mediapanel or PBI/Gemius, list Gemius in the privacy and cookie policies and review the configuration after each TCF or Gemius tag update.
What are the alternatives to Gemius?
Other audience measurement options in Europe include AT Internet/Piano Analytics (France), Etracker (Germany), Mediametrie/NetRatings (France), Adition Audience Measurement and Comscore. For privacy first deployments without panel based profiling, Matomo, Plausible and Fathom remain the simpler choice.
How do I update the cookie policy for Gemius?
List Gemius with the operator (Gemius S.A., Poland), the purpose (audience and ad effectiveness measurement, panel join), the cookies (Gtest, Gdyn, GtestExt) with retention up to 24 months, the legal basis (consent), the IAB TCF vendor ID and the EU only processing location.
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