CookieMop’s default 15-second wait is a configurable safety delay before cleanup, intended to give you a chance to recover from accidentally closing a tab. It starts after the last open tab for a site closes—not after every tab close. The delay is CookieMop’s behavior, not Chrome’s Manifest V3 service-worker timeout.
What happens when you close a tab
CookieMop tracks the sites open in tabs. When the last tab for a site closes, it schedules cleanup after a default delay of 15 seconds. If another tab for that site remains open, the last-tab condition has not been met, so closing one tab does not by itself start that site’s cleanup. The project describes the delay as a configurable “safety net for accidentally closed tabs.” CookieMop’s README says its tabs permission is used to detect tab closures and determine which site a tab belongs to.
Why Manifest V3 makes delayed work tricky
Manifest V3 extensions use event-driven service workers rather than a background page that stays loaded continuously. Chrome says a worker normally terminates after 30 seconds of inactivity. It also documents other termination conditions, including an event or API request running longer than five minutes and a fetch() response taking more than 30 seconds. Those are Chrome lifecycle limits; they are not CookieMop’s 15-second cleanup delay. Chrome’s service-worker lifecycle documentation advises extension developers to account for worker termination and persist state instead of relying on in-memory globals.
Why a plain JavaScript timer is not enough
A setTimeout() or setInterval() created in the worker can be canceled if Chrome terminates that worker before the timer fires. Chrome’s service-worker migration guidance recommends the Alarms API for delayed or periodic operations. CookieMop’s README identifies the alarms permission as the mechanism it uses to fire delayed cleanup reliably.
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The hard part, then, is not waiting 15 seconds in JavaScript while a background page remains alive. It is arranging future work so that the extension can carry it out even if its worker goes dormant in the meantime.
Keep the two 15- and 30-second intervals separate
| Interval | What it means | Source |
|---|---|---|
| 15 seconds | CookieMop’s documented default grace period before cleanup begins; configurable in the project’s description. | CookieMop README |
| 30 seconds | Chrome’s normal service-worker inactivity threshold before termination, subject to lifecycle conditions. | Chrome service-worker lifecycle documentation |
Chrome 120 also changed the minimum alarm period to 30 seconds. That guidance concerns alarm periods; it does not show that CookieMop’s documented 15-second one-shot delay is impossible. The available documentation does not establish the exact scheduling precision for every CookieMop release and supported Chrome version, so do not treat the 15-second setting as a promise of exact-to-the-second execution across versions.
Rank #2
![[2 Pack] 24 Inch Computer Privacy Screen Filter for 16:9 Widescreen Monitor](https://m.media-amazon.com/images/I/41SBKw3J4ML._SL160_.jpg)
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What CookieMop can remove—and the limits to know
CookieMop says cookie deletion is the default. Its README describes options to include localStorage or broader site data such as IndexedDB, CacheStorage, and service workers. Chrome’s browsingData API supports removing these data types, including with origin-scoped removal.
- Cookie scope: Chrome notes that removing cookies for an origin also removes cookies for its registrable domain. An origin-level cleanup may therefore affect more than a single hostname.
- Partitioned cookies: CookieMop’s README says it does not delete CHIPS partitioned cookies because the extension cookies API cannot enumerate them per top-level site.
- Greylisted sites: CookieMop documents cleanup on the next browser startup, and also when the extension is reloaded or updated. That is not necessarily cleanup at the moment the browser closes.
- Removal duration: Chrome says browsing-data removal can take tens of seconds depending on the profile. That is how long removal may take after it begins—not the configured delay before cleanup starts.
What to expect in practice
Think of the 15 seconds as a short grace window after the final tab for a site closes. The Manifest V3 design challenge is preserving the scheduled cleanup across worker suspension; Chrome recommends alarms for this kind of delayed work, and CookieMop documents the alarms permission. The cleanup itself may take additional time, and its scope depends on CookieMop’s settings and the data type involved.
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Best Value
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Rank #4
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