Free tool · Habits & Routines

Habit Density Tracker

Track up to three tiny habits by how many of the last 14 days you showed up, not by how long a streak has run. One missed day moves a number by one instead of resetting everything.

Runs entirely in your browser. Nothing you enter is uploaded, and your habits are saved only on this device.

Your habits

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How to use it

  1. Add a habit. Give it a short name, write its tiny version (the 2-minute version you would still do on your worst day), and write an anchor that starts “After I…”. Pick a weekly target from 3 to 7 days.
  2. Mark the day. Select today’s box when you have done the habit. The tiny version counts. Select any of the last 14 days to fix or backfill it; days 15 to 28 back still count in the four-week trend but cannot be edited.
  3. Read the numbers. Each habit shows days done in the last 7 and 14 days, a four-week trend, and whether you are on target, below it, or just started.
  4. Act on the message, if one appears under the habit’s name.
  5. Check in once a week. Two minutes with the trend is enough, and the weekly review template has a slot for it.

How it works

A streak counts consecutive days, so one miss sets it to zero. Density counts days done inside a rolling window: “12 of the last 14.” The oldest day drops out each day, so a miss lowers the number by one and fades after two weeks.

The evidence for tracking this way is indirect. In seven studies, Silverman and Barasch (2023) found that logs highlighting an intact streak raised later engagement more than logs highlighting a broken one, and the effect was stronger when people blamed themselves for the break. Lally and colleagues (2010) followed 96 volunteers who repeated a daily behaviour for 12 weeks, and a single missed opportunity did not materially affect how the habit formed. We know of no study that compares density with streaks head to head, so treat the design as an inference, not a tested intervention. See the habit-tracking guide and how long it takes to form a habit for the full reasoning.

The messages are rules of thumb

The message under each habit follows four rules, checked in this order:

  • Two or more missed days in a row before today: “Shrink it: restart with the tiny version.”
  • Yesterday missed and today not done: “Re-entry day: do the tiny version today.”
  • Under 3 of 7 days for two weeks running, once the habit is two weeks old: shrink the habit.
  • 5 or more of the last 7 days: keep going.

The thresholds are ours; they echo James Clear’s “never miss twice,” a personal rule, not a research result. Days before you added a habit never count as misses.

Write a tiny version and an anchor

BJ Fogg’s Tiny Habits method splits a habit into an anchor (something you already do), a tiny behaviour, and a celebration, and his own example is flossing a single tooth. Your tiny version is the smallest action that still counts, such as “put on my shoes and step outside” or “write one sentence.”

The anchor turns “I should” into “when this happens, I do that.” Gollwitzer and Sheeran’s 2006 meta-analysis of 94 tests found a medium-to-large effect of if-then plans on goal attainment (d = .65). A 2025 meta-analysis of 642 tests found the plans effective for thoughts, feelings, and actions, with effects between d = .27 and .66. Neither tested a habit tracker, so read them as a reason to write the cue down, not a promise.

Choose a target, and keep to three habits

Pick the number of days you could hit in a rough week, not your best one. A target of 5 allows two off days. After two weeks of logging, raise the target by one day if you cleared it both weeks, and shrink the habit if you missed it both weeks instead of trying harder. The habit-tracking guide has starting targets by habit type.

Three is the maximum because every habit you track adds a daily tap, and James Clear points out that tracking is itself a second habit. The cap is our rule of thumb; we know of no study that gives the right number.

Where your data lives

Habits are saved in your browser’s localStorage under the key lhp.habitTracker.v1, on this device only, and nothing you enter is sent anywhere. Clearing site data deletes the habits. Safari adds a limit of its own: WebKit’s tracking-prevention policy says Safari deletes a site’s script-writeable storage, which includes localStorage, after seven days without you interacting with the site, and exempts Home Screen web apps. WebKit announced the cap in 2020. Browser policies change, so export a JSON copy now and then. Dates follow your device’s calendar.

What it does not do

  • It sends no reminders or notifications. The anchor is the reminder.
  • It has no accounts and no sync, so another device starts empty until you import a file.
  • It records done or not done, not minutes or amounts. There is no excused-day mark, so a day you skip for illness or travel counts as not done.
  • It shows 14 days to edit and four weeks of trend; older days stay in your export.

Frequently asked questions

Does the tiny version count as done?

Yes. The grid records done or not done, so it counts days you showed up. Note full-size sessions in your weekly review if you want them.

Why did it tell me to shrink the habit after two missed days?

Two misses in a row is where our rule switches from “carry on” to “make it smaller.” It is a rule of thumb you can ignore. Two likely causes are a cue that stopped firing and a version that no longer fits your week; the tiny version restarts the habit at a size that survives a bad day.

Should I use it for medication?

No. A weekly target treats some missed days as acceptable, which is the wrong rule for doses. Ask your prescriber or pharmacist what to do after a missed dose.

How do I move my data to another device?

Download the JSON under “Your data,” then paste it or choose the file under Import on the other device. It asks before replacing existing habits.

Related guides

Sources