How it works

A score you can't interrogate isn't worth much. This page documents exactly what Focus Pulse measures, what it deliberately refuses to measure, and how the number on the gauge is calculated.

What counts as browsing time

Time is credited to a site only when all of these hold:

• The site's tab is the active tab in its window.
• A Chrome window actually has focus.
• The system is not idle or locked.

The moment any of those stops being true, the clock stops and the elapsed time is banked against that site's hostname. When they become true again, a fresh session starts.

Pages that are never tracked

Internal browser pages are skipped entirely — chrome://, chrome-extension://, edge://, and about:. Time spent on the new tab page or in your settings is not counted as browsing, and never appears in your statistics.

Hostnames, not URLs

Only the hostname is stored. Reading three different articles on wikipedia.org produces one entry, wikipedia.org, with the combined time. The full address is used momentarily to extract that hostname and is not retained.

Handling absence honestly

The hardest part of a focus tracker is not counting time you weren't there for.

Idle detection runs on a 5-minute threshold. Chrome's idle API only sees physical keyboard and mouse input, so a shorter threshold punishes normal behaviour — reading a long article without touching the mouse would register as absence. Five minutes is the trade-off: genuine idle time takes up to five minutes to be noticed, but ordinary reading is never misclassified.

Audio is treated as presence. If the active tab is playing audio when the system goes idle, tracking continues. Watching a 40-minute talk is engagement, not idling. A locked screen has no such exemption — if you locked the computer, you left.

Brief focus loss has a 300 ms grace period. Opening DevTools or a zoom menu can momentarily unfocus the window. Focus Pulse waits 300 ms and re-checks before deciding the browser genuinely lost focus, so these blips don't shred a session into fragments.

Surviving Manifest V3

Chrome can kill an extension's service worker after roughly 30 seconds of inactivity, and in-memory variables die with it. Focus Pulse treats chrome.storage.local as the only source of truth, and runs a one-minute alarm that checkpoints the session in progress. Without that alarm, a long single-tab session — a video, a long read — would produce no events at all and the time would be silently lost.

Short visits

A session shorter than 10 seconds is recorded as a short visit and costs score points. But this only applies when the session ended because you deliberately navigated away — switched tabs or loaded a new URL.

A session cut short because the browser lost focus, went idle, or was checkpointed by the alarm is not penalised. That is an interruption from outside the browser, not you bouncing between sites, and scoring it as one would punish you for taking a phone call.

The focus score

Every day starts at 100 points and loses points for fragmentation:

score = 100
      − (tab switches      × 1.5)
      − (short visits      × 3)
      − (10 if more than 15 distinct sites were visited)

clamped to the range 0–100, then rounded

Grades and zones

The score maps to a letter grade and a focus zone. They use different boundaries, on purpose — the zone is a coarse read for the gauge, the grade is the finer judgement.

Score	Grade	Zone
90–100	A	Highly focused
80–89	B	Highly focused
65–79	C	Moderately focused
50–64	D	Moderately focused
0–49	D	Distracted

What the formula does not do

This is a v1 heuristic and it is worth being upfront about its limits. The penalties are flat: a tab switch costs the same 1.5 points whether it happened during an hour of deep work or during two minutes of triage. The formula does not currently weight by time of day, by how long a session ran, or by what kind of site was involved. Those are known future improvements, not oversights.

Where the data lives

Each day is stored as a single small record in chrome.storage.local:

Field	Contents
sites	Hostname → milliseconds of focused time
switches	Number of tab switches
shortVisits	Number of sessions under 10 seconds
maxTabs	Highest simultaneous tab count that day

Alongside these sits the in-progress session state — the current hostname and when its session started — which is cleared on every browser restart.

Because several listeners can fire at once (a tab switch, a tab close, and the alarm landing together), all read-modify-write operations on that record are serialised through a queue. Without it, two concurrent updates could silently clobber each other and lose a chunk of your day.

Nothing here is transmitted anywhere. See Privacy for the full statement.