EMZETT.Browser Tab
In short: A single, independently loadable window within a browser that displays its own web page.
In more detail: Modern browsers often isolate tabs into their own processes, so a crashing tab doesn’t bring down the entire browser, and each tab stays separate from other tabs’ resources (also relevant for security — keyword: sandboxing).
In Depth
This process isolation (called “site isolation” in Chrome/Chromium) is a relatively recent development: early browsers ran all tabs in a single process, which saved memory but meant a bug or security problem in one tab could compromise the entire browser or even other tabs. With a dedicated process per tab (or even per website within a tab), the operating system itself can be used for protection — a malicious script on one page can’t easily access the memory of another page open in a different tab this way.
The downside of this isolation is noticeably higher memory usage with many open tabs, since each process brings its own overhead — a well-known criticism of Chrome-style browsers. Many browsers now cushion this by “freezing” inactive tabs (tab discarding/suspending) and only fully loading them again when used once more.
Lifecycle of a tab
Every tab goes through several states: active and visible, in the background but still loaded (JavaScript usually keeps running, though often throttled to save battery/CPU), frozen/suspended (process terminated, only the title and favicon remain), and finally fully closed. Modern browsers prioritise based on usage patterns — a tab not clicked for hours is more likely to be frozen than one that was active just minutes ago. Developers can influence this behaviour via the browser’s Page Visibility API, for example to pause video playback as soon as a tab moves to the background.
Tab groups and session restoration
As the number of tabs grows, many browsers have added organisational tools: colour-coded tab groups, vertical instead of horizontal tab bars for a better overview, or automatic collapsing of rarely used tabs. After a crash or restart, browsers typically save a session (a list of open tabs including URLs) locally and offer a “restore session” feature — technically usually a simple JSON file in the browser’s profile folder, read on the next start.
Cross-site tracking across tab boundaries
Although tabs are isolated at the process level, that doesn’t automatically mean protection against tracking: cookies and other storage mechanisms can be designed so a website recognises whether the same user is also back in another tab (or on a later visit) — exactly what ad networks use for third-party tracking. Modern browsers increasingly restrict this (Safari with Intelligent Tracking Prevention, Firefox with Enhanced Tracking Protection, Chrome gradually with the Privacy Sandbox), by blocking third-party cookies by default or isolating them heavily.