[codethief]

But GP has a point: An IP address (together with a timestamp) may be used to identify you a person but if it's not connected to actual personal data (e.g. what website you visited), "leaking" it to Google doesn't provide Google with any data about you.

I mean, IP address ranges are publicly known. If I now run a `for` loop over all IPv4 addresses and write them to my HDD, am I suddenly illegally storing personal data of all the people behind those IP addresses? Obviously no. An identifier by itself is not worth anything, unless it's connected to actual personal data.

EDIT: Never mind. GP's assumption that "there’s no Referer header - which there won’t be, assuming Referer-Policy is set sanely (which by default it is in all browsers)?" does not seem to hold in my browser. So Google does not only receive the IP address but also the HTTP REFERER.

[latk]

The court judgement addresses this exact point. There are previous judgements (Breyer v Bundesrepublik Deutschland) that establish that dynamic IP addresses are personal data. There are reasonable means to identify the data subject with the help of third parties, such as the ISP. “For this it is sufficient that the defendant has the abstract means for identification of the person behind the IP address. Whether the defendant or Google have the concrete means for linking the IP address with the plaintiff is irrelevant.”

That there is correlating information like timestamps, useragent strings, or referer headers increases the likelihood of actual identification, but the mere reasonable possibility of identification is sufficient for IP addresses to be personal data.

[codethief]

You're missing the point (and mischaracterizing the court decisions): An IP address by itself (without any additional information, e.g. the URL of the website requested by that IP address) cannot possibly be personal data, as was illustrated by my "for loop" example.

The present court case and also the one you're referring to (Breuer v. Bundesrepublik Deutschland[0]) do not say anything to the contrary. They were concerned with situations where there is additional data that could be used e.g. to build a user profile. For instance, the Bundlesgerichtshof judgment addressed the question of "whether dynamic IP addresses of website visitors constitute personal data for website operators" [0] (which clearly know which website the visitor visited and therefore possess additional data about the visitor).

[0]: https://medium.com/golden-data/breyer-are-dynamic-ip-address...

[latk]

I can't agree, but maybe this is semantics :)

For something to be personal data, it must be information that relates to an identifiable natural person. There are two criteria here: (1) it must relate to a natural person, and (2) that person must be identifiable.

Your “loop over IP all addresses”example does not involve personal data because the information doesn't relate to anyone – it is just a list of numbers. Even if it were to relate to individuals, no court would order an ISP to disclose information about corresponding subscribers for such generated IP addresses. Then, the identifiability argument in Breyer cannot work.

In contrast, an IP address that is part of an IP packet received by a server clearly relates to the person sending the packet, if there is such a person. And, with the help of third parties, the person on the other end of the connection is reasonably likely to be identifiable. This does not depend on the website operator having any additional information such as cookie identifiers, other than the date. To avoid confusion, let me quote the relevant part from Breyer:

> 49. Having regard to all the foregoing considerations, the answer to the first question is that [Art 4(1) of the GDPR] must be interpreted as meaning that a dynamic IP address registered […] when a person accesses a website […] constitutes personal data within the meaning of that provision, in relation to that [website] provider, where the latter has the legal means which enable it to identify the data subject with additional data which the internet service provider has about that person.

The only additional data involved here is that held by the ISP, not by the website. That the judgement scopes its conclusion to website providers must be understood not as a limiting factor (as in: IPs can be personal data only for website providers), but as a contrast to the uncontested observation that IPs clearly are personal data for ISPs.

An IP address that relates to an identifiable person is personal data by itself. Thus, its mere disclosure to a third party without a legal basis is a breach of the GDPR. The article you linked highlights the “absolute vs relative” identifiability discussion, but this reasoning holds even under the “relative” standpoint because Google too is a website operator who has the same reasonably likely means for identification as the original website operator, if not substantially better means due to its trove of other data it can correlate with the IP address.

In this LG München case, the court determined that sharing this data with Google was illegal, regardless of whether there is any additional data. It is, in a sense, a very formal argument, that doesn't consider it necessary to dive into specific fact patterns (that's the abstract vs concrete means part quoted in my previous comment). The court did consider the impact of Google's tracking abilities in calculating damages, though.

To summarize my disagreement with your comment: (1) I assert that an IP address by itself can be personal data for a website operator (such as the defendant or Google), per the Breyer argument. (2) The LG München judgement in this Google Fonts case is not concerned about additional data when considering the legality of processing. (3) Additional knowledge held by the website operator is irrelevant for both this case and the Breyer judgement. Since a negative is difficult to prove but a positive can be shown by a single example, could you please point out the paragraphs in the Google Fonts case[1] or the ECJ's Breyer judgement[2] where I'm mistaken for disagreements 2 or 3?

[1] https://rewis.io/urteile/urteil/lhm-20-01-2022-3-o-1749320/

[2] https://curia.europa.eu/juris/document/document.jsf?docid=18...

[Nextgrid]

You are extremely naive if you believe Google can't infer anything if the referer is missing.

An IP + user-agent combination (both of which are sent) is enough to uniquely identify a typical home user with high certainty unless they're behind a carrier-grade NAT and use a very popular browser.

[dlubarov]

Let's assume Google can identify the user but doesn't get a referrer. So what? The only information Google receives is that some user visited some unknown website at a particular time. How exactly would that lead to Google increasing its profits?

[Jensson]

They know users activity hours better that way. At scale that is valuable data.

[codethief]

But that's still not personal data.

[XCSme]

> If I now run a `for` loop over all IPv4 addresses and write them to my HDD, am I suddenly illegally storing personal data of all the people behind those IP addresses

That's actually a good point. The IPv4 space is pretty limited. I guess the GDPR law makes it PII if you bundle both the IP with an action made by that IP (e.g. that IP visited that website).