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Personal data, also known as personal information or personally identifiable information ( PII), is any information related to an identifiable person.
The abbreviation PII is widely used in the United States, but the phrase it abbreviates has four common variants based on personal or personally, and identifiable or identifying. Not all are equivalent, and for legal purposes the effective definitions vary depending on the jurisdiction and the purposes for which the term is being used. Under European Union and United Kingdom data protection regimes, which centre primarily on the General Data Protection Regulation (GDPR), (2025). 9783982417301 ISBN 9783982417301 the term "personal data" is significantly broader, and determines the scope of the regulatory regime.
National Institute of Standards and Technology Special Publication 800-122 defines personally identifiable information as "any information about an individual maintained by an agency, including (1) any information that can be used to distinguish or trace an individual's identity, such as name, social security number, date and place of birth, mother's maiden name, or Biometrics records; and (2) any other information that is linked or linkable to an individual, such as medical, educational, financial, and employment information." For instance, a user's IP address is not classed as PII on its own, but is classified as a linked PII.Section 3.3.3 "Identifiability"
Personal data is defined under the GDPR as "any information which is related to an identified or identifiable natural person". The IP address of an Internet subscriber may be classed as personal data.
The concept of PII has become prevalent as information technology and the Internet have made it easier to collect PII leading to a profitable market in collecting and reselling PII. PII can also be exploited by criminals to stalking or identity theft of a person, or to aid in the planning of criminal acts. As a response to these threats, many website privacy policy specifically address the gathering of PII, and lawmakers such as the European Parliament have enacted a series of legislation such as the GDPR to limit the distribution and accessibility of PII.
Important confusion arises around whether PII means information which is identifiable (that is, can be associated with a person) or identifying (that is, associated uniquely with a person, such that the PII identifies them). In prescriptive data privacy regimes such as the US federal Health Insurance Portability and Accountability Act (HIPAA), PII items have been specifically defined. In broader data protection regimes such as the GDPR, personal data is defined in a non-prescriptive principles-based way. Information that might not count as PII under HIPAA can be personal data for the purposes of GDPR. For this reason, "PII" is typically deprecated internationally.
A term similar to PII, "personal data", is defined in EU directive 95/46/EC, for the purposes of the directive:
In the European Union rules, there has been a more specific notion that the data subject can potentially be identified through additional processing of other attributes—quasi- or pseudo-identifiers. In the GDPR, personal data is defined as:
A simple example of this distinction: the color name "red" by itself is not personal data, but that same value stored as part of a person's record as their "favorite color" is personal data; it is the connection to the person that makes it personal data, not (as in PII) the value itself.
Another term similar to PII, "personal information", is defined in a section of the California data breach notification law, SB1386:
The concept of information combination given in the SB1386 definition is key to correctly distinguishing PII, as defined by OMB, from "personal information", as defined by SB1386. Information, such as a name, that lacks context cannot be said to be SB1386 "personal information", but it must be said to be PII as defined by OMB. For example, the name "Placeholder name" has no meaning in the current context and is therefore not SB1386 "personal information", but it is PII. A Social Security Number (SSN) without a name or some other associated identity or context information is not SB1386 "personal information", but it is PII. For example, the SSN 078-05-1120 by itself is PII, but it is not SB1386 "personal information". However the combination of a valid name with the correct SSN is SB1386 "personal information".
The combination of a name with a context may also be considered PII; for example, if a person's name is on a list of patients for an HIV clinic. However, it is not necessary for the name to be combined with a context in order for it to be PII. The reason for this distinction is that bits of information such as names, although they may not be sufficient by themselves to make an identification, may later be combined with other information to identify persons and expose them to harm.
The scope of the term "sensitive personal data" varies by jurisdiction. In the UK, personal health data is treated as "sensitive" and in need of additional data protection measures.Information Commissioner's Office, Data storage, sharing and security, updated on 30 August 2013, accessed on 7 October 2024 According to the OMB, in the United States it is not always the case that PII is "sensitive", and context may be taken into account in deciding whether certain PII is or is not sensitive.
When a person wishes to remain anonymous, descriptions of them will often employ several of the above, such as "a 34-year-old white male who works at Target". Information can still be private, in the sense that a person may not wish for it to become publicly known, without being personally identifiable. Moreover, sometimes multiple pieces of information, none sufficient by itself to uniquely identify an individual, may uniquely identify a person when combined; this is one reason that multiple pieces of evidence are usually presented at criminal trials. It has been shown that, in 1990, 87% of the population of the United States could be uniquely identified by gender, ZIP code, and full date of birth.
In hacker and Internet slang, the practice of finding and releasing such information is called "doxing". It is sometimes used to deter collaboration with law enforcement. On occasion, the doxing can trigger an arrest, particularly if law enforcement agencies suspect that the "doxed" individual may panic and disappear.
It appears that this definition is significantly broader than the Californian example given above, and thus that Australian privacy law may cover a broader category of data and information than in some US law.
In particular, online behavioral advertising businesses based in the US but surreptitiously collecting information from people in other countries in the form of cookies, Web bug, trackers and the like may find that their preference to avoid the implications of wanting to build a psychographic profile of a particular person using the rubric of 'we don't collect personal information' may find that this does not make sense under a broader definition like that in the Australian Privacy Act.
The term "PII" is not used in Australian privacy law.
Further examples can be found on the EU privacy website.
Additionally, any person may ask in writing a company (managing data files) the correction or deletion of any personal data. Cesla Amarelle, Droit suisse, Éditions Loisirs et pédagogie, 2008. The company must respond within thirty days.
One of the primary focuses of the Health Insurance Portability and Accountability Act (HIPAA) is to protect a patient's Protected Health Information (PHI), which is similar to PII. The U.S. Senate proposed the Privacy Act of 2005, which attempted to strictly limit the display, purchase, or sale of PII without the person's consent. Similarly, the (proposed) Anti-Phishing Act of 2005 attempted to prevent the acquiring of PII through phishing.
U.S. lawmakers have paid special attention to the social security number because it can be easily used to commit identity theft. The (proposed) Social Security Number Protection Act of 2005 and (proposed) Identity Theft Prevention Act of 2005 each sought to limit the distribution of an individual's social security number.
Additional U.S.-specific personally identifiable information (2018). 9781538679319 ISBN 9781538679319 includes, but is not limited to, I-94 records, Medicaid ID numbers, and Internal Revenue Service (I.R.S.) documentation. Exclusivity of personally identifiable information affiliated with the U.S. highlights national data security concerns and the influence of personally identifiable information in U.S. federal data management systems.
The following data, often used for the express purpose of distinguishing individual identity, clearly classify as personally identifiable information under the definition used by the NIST (described in detail below):
The following are less often used to distinguish individual identity, because they are traits shared by many people. However, they are potentially PII, because they may be combined with other personal information to identify an individual.
Another category can be referred to as financial identity theft, which usually entails bank account and credit card information being stolen, and then being used or sold.
Personal data can also be used to create fake online identities, including fake accounts and profiles (which can be referred as identity cloning or identity fraud) for celebrities to gather data from other users more easily. Even individuals can be concerned, especially for personal purposes (this is more widely known as sockpuppetry).
The most critical information, such as one's password, date of birth, ID documents or social security number, can be used to log in to different websites (e.g. password reuse and account verification) to gather more information and access more content.
Also, several agencies ask for discretion on subjects related to their work, for the safety of their employees. For this reason, the United States Department of Defense (DoD) has strict policies controlling release of personally identifiable information of DoD personnel. Many intelligence agencies have similar policies, sometimes to the point where employees do not disclose to their friends that they work for the agency.
Similar identity protection concerns exist for witness protection programs, women's shelters, and victims of domestic violence and other threats.
Writing in 2015, Alessandro Acquisti, Curtis Taylor and Liad Wagman identified three "waves" in the trade of personal data:
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