---
title: "Personally Identifiable Information (PII)"
description: "PII is any data that can identify a person, directly or in combination with other fields. Examples, regulatory definitions, and how to keep it out of AI prompts."
url: "https://sonomos.ai/glossary/personally-identifiable-information/"
source: "https://sonomos.ai/glossary/personally-identifiable-information/"
---

# Personally Identifiable Information (PII)

Any information that can identify a specific person, either directly (name, SSN) or in combination with other data (zip code + birthdate).

## In depth

Personally Identifiable Information (PII) is data that can be used to identify a particular individual. Direct identifiers include names, government IDs, account numbers, biometric data, and contact details. Indirect or quasi-identifiers — birth date, employer, ZIP code, occupation — are PII when combined with enough other fields to single someone out. Most modern privacy regimes (GDPR, CCPA, state laws) regulate PII whether it is direct or indirect, and treat large categories like financial, health, and location data as especially sensitive.

## Examples

- Full name, Social Security Number, passport number, driver's license.
- Email address, phone number, mailing address.
- Combination of date of birth + ZIP code + sex (often re-identifies a single person).
- Account numbers, login credentials, IP addresses tied to an account.

## How Locke handles personally identifiable information (pii)

Locke detects 70+ categories of PII as you type — direct identifiers, financial fields, health-adjacent terms, and contextual matches like client and witness names. Detection happens entirely on your device. Anything flagged can be masked, tokenized, or blocked before it reaches an AI model.

[See the product](https://sonomos.ai/locke/)

## Related terms

- Protected Health Information (PHI)

  Individually identifiable health information held or transmitted by a covered entity, regulated under HIPAA in the United States.
- Redaction

  Removing or blacking-out sensitive content so it is no longer present in the document or prompt.
- Contextual Matching

  Detecting sensitive data by combining structural patterns with surrounding context, instead of relying on regex alone.

## Reading on this topic

- [PHI vs PII vs Personal Data: A Plain-English Compliance Glossary for 2026](https://sonomos.ai/blog/phi-vs-pii-vs-personal-data-glossary/)
- [What Is PII Redaction? A Plain-English Guide for AI Users](https://sonomos.ai/blog/what-is-pii-redaction-ai/)