flashdrop guide — login-free shareable flashcards from a CSV

Updated 2026-05-31 · Runs 100% in your browser, no server or signup.

1. What makes flashdrop different

flashdrop turns a CSV/Excel word list into a login-free, shareable URL flashcard deck. Unlike Quizlet, it never asks you to sign up to create a deck; unlike Anki, there is no app to install or account to sync. The whole point is "share with a single link." Your deck is packed entirely into the share URL (not a server), so you can send the link on any messenger and the recipient studies the same deck instantly.

It fits "share once and move on" situations perfectly — a tutor sending today's vocabulary, or a study group passing a word list around. Because nothing is stored on a server, there is no account or privacy overhead.

2. CSV format — front, back, tag

flashdrop reads one card per line, with columns separated by a comma or a tab:

• Column 1 — front: the prompt (e.g. an English word, a question)
• Column 2 — back: the answer (e.g. the meaning)
• Column 3 — tag (optional): a label for grouping (e.g. part of speech)

front,back,tag
apple,사과,fruit
run,달리다,verb
"hello, world","안녕, 세계",greeting

If the first line looks like a header (front,back,tag), it is skipped automatically — but a header is not required. To include a comma, quote, or line break inside a cell, wrap the cell in double quotes; to include a literal quote, double it as ""(standard CSV, RFC 4180). To import from a spreadsheet, either save as CSV UTF-8, or just copy two columns and paste them into the "Paste as text" box (tab-separated input is detected automatically).

3. Build and share — how server-less URL sharing works

After you upload or paste, the page shows the number of cards detected and a preview. Enter a title, press "Build flashcards," and the URL becomes ?d=.... Thatd value contains the entire deck compressed with lz-string into a URL-safe string. Press "Copy share link" and send it — the recipient opens it with no signup.Nothing is stored on a server, which also means spam/abuse decks never accumulate. The trade-off: if you lose the link, you must rebuild it from the original file.

4. SM-2 spaced repetition — how it works

flashdrop uses the SM-2 algorithm from SuperMemo (1987). It shows a correctly-recalled card at growing intervals and a missed card again the next day, scheduling reviews just before you would forget. The four grading buttons map to SM-2 grades:

• Again (grade 0): missed → streak resets and the card returns tomorrow.
• Hard (grade 3): barely recalled → counts as correct but lowers the ease factor.
• Good (grade 4): recalled normally.
• Easy (grade 5): recalled easily → raises the ease factor, widening the next interval.

Intervals are computed as: 1st correct → 1 day, 2nd → 6 days, then previous interval × ease factor. The ease factor starts at 2.5 (floor 1.3) and is tracked per card, so easy cards space out quickly while tricky cards keep coming back.

5. Using the study screen

• Flip: click the card or press Space.
• Move: ← / → or the Prev/Next buttons.
• Grade: with the back showing, keys 1–4.
• Shuffle, Weak only (review just the cards you last missed).
• Pronounce 🔊: reads the front via the browser's Web Speech API (supported browsers).
• Weak cards CSV: download just the not-yet-learned cards.

6. Where progress is stored

Your study progress lives only in this browser's localStorage — never sent to a server. Reopen the same link on the same device and you continue where you left off. Progress is keyed by a short hash of the deck content, so changing the cards starts a fresh record. Private/incognito mode, other devices, or clearing browser data will not carry progress over; export the weak cards as CSV if you need a backup.

7. Handling large decks (long links)

Because the deck travels inside the URL, more cards mean a longer link. lz-string compresses it a lot, but a few hundred cards can exceed what some messengers' link previews accept. The builder warns you when the link gets long; in that case, split the deck by topic into several shorter links. Reducing repetitive text also helps it compress better.