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Spaced Repetition Learning ​

Web Highlights turns your highlights into flashcards and uses spaced repetition to help you move knowledge from short-term into long-term memory. Instead of forgetting 80 % of what you read, you review at scientifically optimized intervals and remember it for good.

The Problem: The Forgetting Curve ​

In 1885 Hermann Ebbinghaus discovered that we lose most of what we learn within days unless we actively review it. His research produced the forgetting curve — a chart showing how retention drops exponentially over time:

The Forgetting Curve — retention drops over time without review

The key insight: each review resets the curve and makes the next one shallower. After roughly five well-timed repetitions, information is considered anchored in long-term memory.

How Spaced Repetition Works ​

Spaced repetition schedules reviews at increasing intervals. Rather than cramming everything in one sitting, you revisit material right before you are likely to forget it:

ReviewTypical interval
1st1 day
2nd3 days
3rd7–10 days
4th~30 days
5th+60–360 days

The exact intervals adapt to your performance — items you know well are pushed further out, while items you struggle with come back sooner.

Why it works

A meta-analysis across over 1,350 participants confirmed that spaced practice produces significantly better long-term retention than massed (crammed) practice, with a strong effect size of g = 0.74. (Cepeda et al., 2008; Educational Psychology Review, 2020)

The SuperMemo Algorithm ​

Under the hood Web Highlights uses a variant of the SuperMemo (SM-2) algorithm, originally developed by Piotr Woźniak. Here is how it works in practice:

Easiness Factor (EF) ​

Every highlight starts with an easiness factor of 2.5. After each review the EF is adjusted based on your self-rated performance:

  • "Know it" → EF increases, interval grows (you remembered well)
  • "Don't know" → EF decreases, interval shrinks (needs more practice)

The EF never drops below 1.3 (to avoid frustratingly short intervals) and can rise up to 3.2 for material you consistently recall.

Interval Calculation ​

The next review date is calculated as:

next interval = current interval × EF

For example, if your current interval is 3 days and EF is 2.5, the next review will be scheduled in roughly 8 days. Intervals are capped at 360 days maximum.

Confidence Score ​

Web Highlights derives a confidence score (0–100 %) from the EF and number of repetitions. This score is displayed for each highlight and aggregated per website, tag, and across your entire library:

ConfidenceStatus
80–100 %Long-Term Memory
60–79 %Confident Recall
40–59 %Good Recall
20–39 %Moderate Recall
1–19 %Likely to Forget
0 %Not Yet Learned

Learning Sessions ​

A learning session presents 10 flashcards per review — a mix of due items (scheduled for review today) and new items (never reviewed before).

During a Session ​

For each card you see the highlighted text in context, along with the source page. You then choose one of three actions:

  • Know it — You remembered the content. Confidence increases, and the next review is pushed further into the future.
  • Don't know — You could not recall the content. Confidence decreases, and the item is rescheduled for an earlier review.
  • Discard — Remove this highlight from future sessions entirely.

After a Session ​

A summary shows how many cards you reviewed, how many you knew, and your current learning streak — the number of consecutive days you have completed a session.

Learning Streaks ​

Completing at least 10 cards per day counts toward your daily streak. The learning dashboard tracks your current streak, longest streak, and a contribution graph showing your learning activity over time.

Daily Reminder

You can enable a daily email reminder to nudge you into starting your learning session — helpful for building the habit in the first few weeks.

Learning Dashboard ​

The learning dashboard gives you a full overview:

  • Schedule — Cards due today, tomorrow, and total counts
  • Confidence breakdown — Distribution of your highlights across confidence levels
  • Categories — Filter your flashcards by website or tag
  • All highlights — A sortable list of every learning item with confidence, next review date, and source

Getting Started ​

  1. Highlight text on any webpage or PDF
  2. Open the Learning Dashboard from the sidebar or web app
  3. Start a learning session and rate each card
  4. Come back daily — even 2–3 minutes a day builds lasting knowledge

INFO

The learning feature is available on all platforms — the browser extension sidebar, the web app, and on mobile.

Further Reading ​