Anki Flashcards

Create flashcard decks, study with the SM-2 spaced repetition algorithm and track your retention over time.

Ready-to-use decks

Choose a sample deck or create your own.

My decks

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Select a deck to study.

📖 Select a deck in the My Decks tab and click Study now.

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Export current deck

Save the selected deck as JSON (preserves SM-2 progress) or TSV (compatible with Anki Desktop).

Import deck

Import a previously exported JSON file or a TSV (Anki-compatible). New decks are added without overwriting existing ones.

📂 Choose file (JSON or TSV)

Export ALL decks

Full backup — saves all your decks and progress in a single JSON file.

📊 Decks overview

📚 Add or select a deck to see your stats here.

📈 Active deck progress

No deck selected.

⌨️ Keyboard shortcuts

Space / Enter	Flip card
0 – 5	Grade: 0=Forgot … 5=Perfect
← →	Previous / next deck

What is spaced repetition?

Spaced repetition is a learning technique based on cognitive science: instead of studying the same material every day, you review cards at increasing intervals — right before you’re about to forget them. This dramatically reduces the total study time needed while achieving far higher long-term retention than traditional cramming.

Studies consistently show that spaced repetition produces retention rates above 90% with a fraction of the review time compared to massed practice.

The SM-2 Algorithm

This tool implements SM-2 (SuperMemo 2), the algorithm behind the original Anki Desktop application. Every card has two key parameters:

Ease Factor (EF): starts at 2.5. Reflects how easy the card is for you. Higher EF → longer next interval.
Interval: days until next review. Starts at 1 day, then grows based on your grades.

Grading scale (0–5)

Grade	Meaning
0	Complete blackout — no memory at all
1	Incorrect, but the answer felt familiar
2	Incorrect, but the answer was easy to recall upon seeing
3	Correct, but required significant effort
4	Correct, with slight hesitation
5	Perfect recall — instant and effortless

How the next interval is calculated

I(n) = \begin{cases} 1 & \text{if } n = 1 \\ 6 & \text{if } n = 2 \\ I(n-1) \times EF & \text{if } n \geq 3 \end{cases}

Any grade below 3 resets the card to the beginning (interval = 1 day, repetitions = 0).

Ease Factor update

EF' = \max\!\left(1.3,\; EF + 0.1 - (5 - g)(0.08 + (5 - g) \cdot 0.02)\right)

Where $g$ is your grade (0–5). Lower grades decrease EF, making future intervals shorter.

Response Time Integration

Beyond the grade, this tool also measures retrieval latency — the time from when the card front appears until you flip it. This time is incorporated into the SM-2 update to capture not just whether you remembered, but how quickly.

Speed tiers

Response time	Modifier	Badge
< 3 seconds	+0.10 EF	⚡ Fast
3 – 8 seconds	0.00	✅ Normal
8 – 20 seconds	−0.10 EF	🐢 Slow
> 20 seconds	−0.20 EF	🔴 Very slow

Full formula with speed modifier

EF' = \max\!\left(1.3,\; EF + 0.1 - (5-g)(0.08 + (5-g)\cdot 0.02) + \Delta_{speed}(t)\right)

Numeric example — grade 4, response time 2.5 s:

EF' = \max(1.3,\; 2.50 + 0.1 - (1)(0.08 + 0.02) + 0.10) = 2.60

Exponential weighted moving average (EWM)

Response time is smoothed per card using EWM with $\alpha = 0.3$ :

\bar{t}_n = 0.7 \cdot \bar{t}_{n-1} + 0.3 \cdot t_n

This prevents a single unusually fast or slow response from distorting the card’s historical average.

Scheduling Algorithm

Cards in the Scheduled Review queue are sorted as follows:

New cards (never reviewed) appear first — FIFO order by creation date
Due cards (interval expired) are sorted by how overdue they are — most overdue first

This ensures you always prioritize the cards you’re most at risk of forgetting.

Statistics & Charts

Deck-level stats

Each deck displays six live stats:

Stat	Description
Due	Cards whose review interval has expired today
New	Cards never reviewed
Learning	Cards reviewed at least once, interval ≤ 21 days
Mature	Cards with interval > 21 days
Retention	% of reviews with grade ≥ 3
⏱ Avg. time	Exponentially weighted average retrieval time

Session stats

After each session the tool shows:

Total cards reviewed
Session average retrieval time
Current deck retention (scheduled mode only)

Charts

The Active Deck Progress panel renders three charts inline:

Interval distribution — bar chart showing how cards are distributed across interval buckets (New, 1–3d, 4–7d, 8–21d, 22–60d, >60d)
Response time — distribution across speed tiers (Fast / Normal / Slow / Very slow)
Ease Factor — distribution of EF values across the deck

These charts are also included in the PDF Report generated from the Import/Export tab.

How to Use

Tab 1 — My Decks

Ready-to-use decks: add any of the 4 preset decks (Basic Math, Spanish Vocabulary, Human Anatomy, Programming Concepts) in one click.
My decks: shows all your decks with retention % and due card count.
Click any deck to select it as the active deck.
+ New empty deck: opens a modal to name your deck. Includes an AI prompt template.

Tab 2 — Study

Select a deck and the Study tab shows the setup screen.
Choose mode:
- Scheduled review — only due cards; SM-2 progress is saved.
- Free practice — any card in the deck; no SM-2 update.
Filter by tag to study a subset of cards.
Set the number of cards and whether to shuffle.
Click ▶ Start session.
Read the front, press Space/Enter (or click Flip) to reveal the back.
Grade yourself 0–5. The speed badge appears after flipping.
At the end, export your deck or start a new session.

Action buttons during study:

Button	Action
↩ Undo	Reverts the last grade (SM-2 + study log restored)
☁ Bury	Skips the card until tomorrow without changing SM-2
🚫 Suspend	Removes the card from all queues indefinitely
✏️ Edit	Edit front and back inline without leaving the session

Tab 3 — Editor

Add cards with front, back and tags.
Search cards by text.
View per-card stats: interval, repetitions, EF, lapses and average response time.
Badges show 🩸 Leech, 🚫 Suspended, and ☁ Buried status.
Click ⚙️ Settings (next to Rename) to configure per-deck options.
Delete individual cards or the entire deck.

Deck Settings

Field	Default	Description
New cards per day	20	Max cards with 0 repetitions per scheduled session
Leech threshold	4	Number of incorrect answers to flag a card as 🩸 Leech

Tab 4 — Import / Export

Action	Format	Details
Export deck	JSON	Preserves all SM-2 data
Export deck	TSV	Anki Desktop compatible
Export deck	HTML/PDF	Opens print dialog with charts
Export all	JSON	Full backup of all decks
Import	JSON or TSV	Adds new decks without overwriting existing ones

Streak & Study History

After studying, the result panel shows a streak (consecutive days with at least one review) and a 28-day heatmap showing review frequency by day. Useful for tracking consistency.

Review Forecast

The 📅 Review forecast chart shows how many cards become due over the next 14 days based on current SM-2 intervals. Use it to plan longer or lighter sessions.

Cloze Cards

Use {{answer}} inside a card’s text to create fill-in-the-blank cards:

Front: The capital of France is {{Paris}} → displays The capital of France is [...]
Back: highlights the answer in green — Paris

Multiple {{...}} in the same card are all masked at once.

Generating Decks with AI

Open the + New empty deck modal, expand the 🤖 Generate cards with AI section, and copy the prompt. Paste it into ChatGPT, Claude or Gemini. Save the response as deck.tsv and import it in the Import/Export tab.

The prompt instructs the LLM to produce a properly formatted TSV file with #separator:tab and #html:false headers — fully compatible with Anki Desktop and this tool.

TSV File Format

#separator:tab
#html:false
Front text	Back text	tag1 tag2
What is REST?	Architectural style for HTTP APIs using GET/POST/PUT/DELETE	web api

Separator: tab character (\t)
First line: #separator:tab
Second line: #html:false
Columns: Front \t Back \t Tags (tags are space-separated)
Compatible with Anki Desktop’s File → Import dialog

Tips

Keyboard shortcuts: Space/Enter to flip, 0–5 to grade, ← → to switch decks.
Daily habit: even 5–10 minutes of scheduled review is far more effective than long occasional sessions.
Grade honestly: overrating yourself (always pressing 5) will inflate intervals and hurt long-term retention.
Free practice before an exam: use free practice mode to review any card without affecting your SM-2 schedule.
Leeches are signals: if a card becomes a leech (🩸), rethink the question — it’s probably too vague or covers more than one concept.
New cards per day: keep this at 10–20 to avoid overwhelming future review queues.
Shared data: the PT (Portuguese) and EN versions of this tool share the same localStorage data — your decks appear in both.

Frequently Asked Questions

Does this tool work offline? Yes. All logic runs in the browser. Your deck data is stored in localStorage — no server required.

Will my decks be lost if I clear browser storage? Yes. Export a JSON backup regularly via the Import/Export tab to avoid data loss.

Can I import decks from Anki Desktop? Yes — use Anki Desktop’s File → Export → Notes in Plain Text (.txt) with the tab separator option. Import the resulting file here.

What is a “mature” card? A card whose interval is greater than 21 days. Mature cards indicate solid long-term learning.

What is the maximum interval? There is no hard cap. After many successful reviews a card can reach intervals of 6 months, 1 year or more.

Why does grading 5 sometimes increase EF by less than expected? The speed modifier applies on top of the grade modifier. A grade-5 with a very slow response (>20 s) will have its EF reduced by 0.20, partially offsetting the grade bonus.

Is the data stored on a server? No. Everything stays in your browser’s localStorage. Nothing is transmitted externally.

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