Let idle tabs take a nap.
Siesta unloads Firefox tabs you haven't used for a while, so their memory is freed –
and you decide for every tab how long that while is.
Get it for Firefox · How it works · FAQ · Development
- A timer for every tab – keep Microsoft Teams loaded for 10 minutes after you leave it, a news site for an hour, and never touch your music tab. Pick never, 5, 10, 15 or 30 minutes, 1 or 2 hours, or any custom time up to 24 hours.
- Site rules – one timer for every tab of a site, e.g.
teams.microsoft.com. - A default, if you want one – for all tabs without their own rule (off out of the box).
- Everything in the popup – current tab, timers, overview, stats and settings live in the toolbar popup. There is no separate options page.
- Live overview – which tabs are loaded and which are unloaded, a countdown for each tab and the one that unloads next. A small moon wanes as a tab gets closer to its nap.
- Unload by hand – a single tab, the tab you're on, or every inactive tab at once; also from the tab context menu, for several selected tabs.
- Stays out of your way – tabs playing audio and tabs sharing your camera, microphone or screen stay loaded. Pinned tabs only unload with their own or a site rule.
- Stats – unloads of the last 7 days, the sites unloaded most often, recent unloads and how many unloaded tabs you opened again later.
- Private – no data collection, nothing is sent anywhere.
 The current tab – pick its timer |
 Overview – countdowns and unloaded tabs |
 Any tab – own rule or site rule |
 Stats – a week of unloads |
 Settings – right in the popup |
 Light and dark – follows Firefox |
Tab titles and numbers in the screenshots are made up.
From Firefox Add-ons: addons.mozilla.org/firefox/addon/siesta-tabs – requires Firefox 142 or newer on the desktop.
From source, for a test run (gone after a browser restart): clone this repository,
open about:debugging#/runtime/this-firefox, click Load Temporary Add-on… and pick
manifest.json.
- The idle clock starts when you leave a tab – Firefox records that moment for every tab. The tab you're on, in any window, is never unloaded automatically.
- Which timer applies: a tab's own rule beats a site rule, which beats the default. Never is a rule too, so you can exempt one tab from a site rule or the default.
- When the time is up, Siesta asks Firefox to unload the tab (
tabs.discard). It stays in the tab bar with its title and icon; clicking it loads the page again. - What keeps a tab loaded: playing audio or sharing camera, microphone or screen (when audio stops, the clock starts over), being pinned (unless the tab has its own or a site rule), or the pause switch in the popup header.
Tab rules are stored with the tab in Firefox's session data, so they survive a browser restart; site rules, settings and stats are kept in the add-on's local storage. Siesta checks timers with alarms timed to the next due tab, plus a sweep once a minute.
How much memory does this save?
It depends on the page – a web app like Teams usually holds far more than a plain
article. Firefox doesn't tell add-ons how much memory a single tab uses, so Siesta shows
no RAM figures rather than made-up ones. about:processes in Firefox shows the real
numbers.
Do I lose anything when a tab is unloaded?
The tab keeps its history and scroll position. Firefox restores text you typed into forms on most pages, but not on every one – give tabs with unsaved work a longer timer or Never. While a tab is unloaded it can't do anything in the background: an unloaded Teams or mail tab sends no notifications until you open it again.
Can I unload the tab I'm on?
Yes, with the moon button in the popup or Unload now in the tab context menu. Firefox can't unload the selected tab, so Siesta first switches to the tab you used before.
Does it work in private windows?
Only if you allow it: about:addons → Siesta → Run in Private Windows.
Why these permissions?
| Permission | Used for |
|---|---|
tabs |
Reading tab titles and addresses for the list and for site rules |
storage |
Settings, site rules and stats |
alarms |
Unloading tabs on time |
sessions |
Keeping a tab's own rule across browser restarts |
menus |
The Siesta entry in the tab context menu |
Siesta is plain JavaScript without a build step – what's in the repository is what Firefox runs.
npm ci # web-ext and puppeteer-core for the tests
npm start # Firefox with the add-on loaded (web-ext run)
npm run lint # Mozilla's add-on linter
npm test # unit tests for the timer logic
npm run test:e2e # end-to-end test in a headless Firefox (about 90 s)
npm run build # unsigned dist/siesta-<version>.xpi for testing
npm run publish # submit to addons.mozilla.org (asks for your API key)| Path | What it does |
|---|---|
background.js |
Timers, unloading, stats, toolbar badge, tab context menu |
lib/core.js |
Shared logic: resolving rules, tab status, formatting |
popup/ |
The popup: current tab, tab list, stats and settings |
tests/ |
Unit tests and the headless Firefox test, which also renders the screenshots |
amo-metadata.json |
Listing text for addons.mozilla.org |
The end-to-end test runs a copy of the add-on in Firefox through WebDriver BiDi, sets
real one-minute timers and checks that the right tabs get unloaded.
node tests/e2e.mjs --shots docs/images [--dark] renders the screenshots above.
- Typeface: Bricolage Grotesque by the
Bricolage Grotesque Project Authors (Atelier Triay), SIL Open Font License 1.1
(
fonts/OFL.txt).