Privacy Glossary

Privacy settings menus are full of terms that are rarely explained where you actually encounter them. This page collects the ones that come up most often across our guides, in plain language, with links to where each concept matters in practice.

App Tracking Transparency (ATT)

Apple's iOS requirement that apps must ask permission before tracking you across other companies' apps and websites for advertising. It appears as a system prompt ('Allow Tracking?') the first time an app wants to do this, and you can also deny it in bulk for all apps at once in Settings.

Appears in: iOS privacy guide , Instagram privacy guide

ACR (Automatic Content Recognition)

A feature built into nearly every modern smart TV that samples what is on your screen, from any source, and matches it against a reference database to identify exactly what you are watching. It feeds advertising and recommendation systems and is turned on by default on almost every major brand.

Appears in: Samsung TV privacy guide , LG TV privacy guide , Roku privacy guide , Is my smart TV watching me?

Fingerprinting

A tracking technique that identifies your browser or device using a combination of otherwise-ordinary details, like screen size, installed fonts, timezone, and browser configuration, without using cookies at all. Because it does not rely on stored identifiers, it survives clearing cookies or using private browsing, which is what makes it harder to block than cookie-based tracking.

Appears in: Chrome privacy guide , Firefox privacy guide , Safari privacy guide

Telemetry

Diagnostic and usage data that software sends back to its maker automatically, covering things like crash reports, performance metrics, and feature usage. Some telemetry is genuinely useful for fixing bugs; the amount collected and how clearly it is disclosed varies a lot between companies, and most systems let you reduce it to a minimal or required-only level.

Appears in: Windows 11 privacy guide , Firefox privacy guide , Edge privacy guide

End-to-end encryption (E2EE)

A form of encryption where only the sender and recipient hold the keys needed to read a message, meaning the service carrying it, including the company that built the app, cannot decrypt the content even if legally compelled to hand it over. It protects message and call content specifically; it does not by itself hide metadata like who you talked to and when.

Appears in: WhatsApp privacy guide , Can WhatsApp read my messages?

Metadata

Data about your communication rather than its content: who you contacted, when, how often, for how long, and sometimes your approximate location. End-to-end encryption typically protects message content but not metadata, so a fully encrypted conversation can still reveal a meaningful amount about your relationships and habits.

Appears in: WhatsApp privacy guide , Can WhatsApp read my messages?

Privacy Sandbox

Google's ongoing effort to replace third-party cookies in Chrome with a set of alternative, browser-managed advertising technologies, such as Topics, which shares a small set of interest categories with sites instead of a persistent per-site identifier. It is a change in tracking method, not a removal of ad targeting, and it remains actively debated among privacy researchers.

Appears in: Chrome privacy guide , Google account guide

Advertising ID

A unique, resettable identifier assigned to your phone (Google's Advertising ID on Android, Apple's Identifier for Advertisers on iOS) that apps and ad networks use to recognize you and build a profile across apps without knowing your name. Both platforms let you delete or limit it, which is one of the highest-impact single settings on a phone.

Appears in: Android privacy guide , iOS privacy guide

Data broker

A company that collects personal information, often from public records, apps, loyalty programs, and other data brokers, and compiles or resells it, typically for advertising, marketing, or background-check purposes. Most people never interact with data brokers directly; the data usually arrives there as a byproduct of something else, like a smart TV reporting viewing habits or an app sharing location data.

Appears in: Samsung TV privacy guide , Does Instagram listen to your microphone?

Off-platform activity

Data a company collects about you from sources outside the app or site you are directly using, such as a pixel embedded on a retailer's checkout page, a purchase a store shares under a data partnership, or activity on a sibling app under the same parent company. It is a major reason ad targeting can feel like it knows more about you than you ever told the app itself.

Appears in: Meta account guide , Instagram privacy guide

AI training opt-out

A setting, where one is offered, that excludes your conversations, uploads, or content from being used to train an AI company's future models. It is commonly opt-out rather than opt-in on consumer tiers, meaning it is on unless you turn it off, and it usually only affects future use rather than removing anything already incorporated into a trained model.

Appears in: ChatGPT privacy guide , Does ChatGPT train on your conversations?

Ephemeral / disappearing messages

A messaging feature that automatically deletes messages from a conversation after a set time, ranging from 24 hours to a few weeks depending on the app. It reduces how much conversation history sits on devices and in backups indefinitely, though it does not stop a recipient from taking a screenshot before a message disappears.

Appears in: WhatsApp privacy guide