Dual Dictionary

Learn workplace English where the network drops. Prepare packs where you have a connection; then read, practise and review fully offline — no key, no account, no tracking.

📚 Offline lessons (33 packs · ~340 KB) 📝 IELTS/TOEIC offline lab

Reading to speaking practice

AI suggestions are checked against your reading. Review feedback before saving it to your study history.

Save this meaning

Choose the dictionary entry you are viewing. The full definition and source are saved on this device; edit the text if you want to keep one specific sense.

Connect your AI account

This is optional. Offline study stays free. Your key stays in this browser and is sent only to the provider you choose after you approve each request. The provider may charge for tokens.

Advanced: model and endpoint

Choose dictionaries to download

No dictionary is loaded yet — pick the dictionaries you need and download them once.

One-time download, stored in the app, fully offline afterwards.

WordNet 3.1 WordNet licence not loaded
Simple English Wiktionary CC BY-SA & GFDL not loaded

A study & research dictionary, right in your browser

About this app — features & terms of use

Dual Dictionary is an offline-first web app built for personal study and research: it looks up English words across several dictionaries with one-tap panel switching, and supports your own .mdx/.mdd dictionary files. Everything runs in your browser — data stays on your device, no account, no tracking, no ads.

This app is provided for personal study and research purposes only. It is not a commercial product and is not intended for commercial use or redistribution of any dictionary content. The bundled open data remains available under its own licenses (see NOTICE.md) — this term applies to this deployment only.

  • Multi-dictionary lookup: one search — tap a tab to switch the dictionary you are reading.
  • Reader mode: paste an article or load a Wikipedia page, then tap any word to look it up in the panels below — without leaving the text.
  • Open by default: the public edition ships with open-licensed dictionaries (WordNet 3.1, Simple English Wiktionary) — free for everyone, no login. You can also add the open English–Vietnamese dictionary (OVDP, 386,600 entries) in one click.
  • Bring your own dictionaries: load any .mdx / .mdd file (MDX format) you own, e.g. learner's dictionaries, into either panel — only files you are authorized to use.
  • Learn-oriented tools: word suggestions, search history, a Vault that keeps every word, phrase and sentence with your notes and tags, and a spaced-repetition Review queue that can re-fit its FSRS weights to your own history (on-device, from ⚙ Advanced, once enough reviews accumulate).
  • Context that sticks: look up a saved word and see your own original sentence highlighted above the entry — add extra examples any time.
  • Practice & track: turn saved items into quick practice sessions (fill in the gap, listen & type, say it aloud with your browser's speech recognition) and watch words learned, retention and sources in Stats. Review runs on the FSRS scheduler, and real IPA is shown for most English words. Practice also has 🎤 cue cards (prompt, 1-minute prep, 2-minute speak); the Reader shows your live reading pace, and the Vault has a ✍ journal with a word count and an IELTS Task 2 timer.
  • Offline lesson pipeline: 33 reviewed workplace + academic packs (~10KB each) — install once at Lesson Studio, then read, practise and review fully offline. IELTS/TOEIC lab in Practice works offline with fixed answer keys.
  • Learning guides: 34 developer-written posts (VI) with English summary — study method, TOEIC night-shift setup, 30-day pack plan.
  • Your data is yours: export / import Vault items as JSON, CSV, TSV or Anki-ready text — no cloud or account for your study data. Optional AI sends your article and answers to your chosen provider after you agree; you pay that provider for tokens.
  • Install like an app: Add to Home Screen on iOS/Android — works fully offline after that. Optional review reminders (opt-in, local-only) can be enabled in ⚙ Advanced.

Dictionaries & licenses

The public edition ships only open-licensed data (see NOTICE.md):

Commercial dictionaries (e.g. OALD, LDOCE) are never bundled here; load your own files via ⚙ Advanced only if you are authorized to use them.

If this app helps your study, I'd genuinely like to hear it — one email is enough.

Edit item

Add an example

Your own example sentence for “”.

Export

Fields

Passphrase

Tags

Rename or delete a tag across all saved items.

Welcome 👋

  1. Look up — type a word, then tap a dictionary tab to read its result; switch anytime. Prefer meanings in your language? Add the Vietnamese dictionary in one click.
  2. Read & save — open 📖 Reader, paste an article (or a Wikipedia URL), tap any word to look it up. Save the word with ☆, or ⭐ save the whole sentence.
  3. Review & practice — your saved items live in ★ Vault: filter, tag, sort. 🔁 Review runs a spaced-repetition queue; 🎯 Practice turns it into quick drills.
  4. Make it yours — switch theme (🌓) or the navigation language (EN/VI); turn on optional review reminders in ⚙ Advanced; dictionary lookup, saving and review work offline for free. Optional AI practice needs internet and your own provider key. You pay the provider for tokens; article text and answers are sent only after your agreement.
  5. New: daily word, quizzes & level test — 📅 Word of the day under the search box (1 word/day at your level + streak); 🎯 Practice has Vault quizzes (flashcards, listen-type, multiple choice); 📊 Level test (20 questions) sets your level and picks the right deck. 🎤 Voice search in the search box; 🔗 Share link in Export sends a word list to friends (no account).

Saved articles

Articles you saved for offline reading. Tap one to load it into the Reader — no network needed.

How to use

📘 Mở hướng dẫn sử dụng đầy đủ bằng tiếng Việt

  1. Wait for the first download — the dictionaries are fetched once, then stored in the app and work offline. Progress, speed and time remaining are shown in each panel header; you can cancel or retry from the start screen.
  2. Type a word (e.g. apple) and press Enter — tap a tab above the result to switch dictionaries.
  3. Read & tap — open 📖 Reader, paste an article (or load a Wikipedia URL), then tap any word to look it up below without leaving the text. 🎬 YouTube transcript turns a video's captions into the same tappable text.
  4. Save a meaning — ☆ opens loaded dictionary entries. Choose the source and edit the full definition if you want one sense per card. Reader also keeps the tapped sentence; ⭐ Save sentence saves that sentence by itself.
  5. Review — open ★ Vault to browse meanings with their saved source and sentence, notes, tags and filters, then 🔁 Review runs the FSRS spaced-repetition queue — after a few hundred graded reviews, ⚙ Advanced can re-fit its weights to your own history (entirely on this device).
Offline IELTS, TOEIC, Writing and Speaking practice
  1. Open Practice and choose IELTS Academic or TOEIC Listening & Reading, then choose Listening, Reading or all objective questions. The versioned original content pack works offline and demonstrates multiple choice, audio choice, short answer, gap-fill and matching; it is not official exam material.
  2. For TOEIC Part 1, play each bundled statement from its audio control and choose the one that matches the picture. These original audio clips are precached with the app and work offline. Other listening examples reveal their transcript after practice; optional browser voice playback depends on installed voices.
  3. Choose Practice for feedback after every answer or Timed practice · current question set to move between available questions, go back, skip, and submit against a countdown. Timed pathway practice scales to the selected set. IELTS Academic diagnostic mode has 40 Listening questions in four Parts and 40 Reading questions in three passages, with 30- and 60-minute section timers; both can be completed in one 90-minute objective-only session. Browser-generated Listening voice is synthetic, and the authored items are not calibrated, so results suggest a next stage per skill rather than a predicted or overall band. TOEIC remains a short starter bank (8 Listening and 8 Reading questions). Answers stay hidden until submission; reloading preserves the selected skill, question, answers and remaining time. Progress shows local raw answers by skill, never an official score.
  4. IELTS Academic Writing prompts cover Task 1 and Task 2, and Speaking prompts cover Parts 1–3. Drafts save on this device. Use the checklist for self-review, then save an attempt to offline history. The TOEIC set intentionally covers L&R; TOEIC Speaking and Writing are separate tests and are not included.
  5. Optional AI feedback for Writing/Speaking uses the provider and API key you configured in Advanced → Learning. It requires internet, your per-request consent, and may incur token charges with the provider. Writing sends the prompt and your response; Speaking sends only your prompt and typed transcript/notes. Recordings never leave the device through this feature. Feedback is for practice and does not predict an official score. Prompts, drafts, self-review and saved recordings remain available offline without a key.
  6. Speaking prompts can be recorded with your microphone; recordings are stored on this device (maximum 25 MB each) and included in JSON/encrypted study backups. Microphone access needs a secure browser context and your permission. Speech recognition is optional and may contact the browser vendor online; this app does not guarantee offline transcription.
  7. In Reader → Listening, save your own audio file and transcript to keep them for later offline sessions. The audio stays local. Include your saved study data in a JSON or encrypted backup before moving devices; media makes the file larger. You can delete saved materials and recordings from their lists.
  8. Vault’s Journal tab remains available even when you have no saved vocabulary. Journal text and its timer resume after reload on this browser.
📚 Learning guides — 34 posts by the developer (EN summary)

Study method, TOEIC and IELTS guides in Vietnamese (~48,000 words), with an English summary page. New: how work readings become offline packs, 30-day pack plan, night-shift TOEIC setup. Full list: Blog học IELTS & TOEIC.

Optional AI practice — setup, privacy and costs

Dictionary lookup, Reader, Vault and review remain free and offline after setup. AI practice is optional, requires internet for new responses and uses an API key for your chosen provider. Token charges are paid directly to that provider.

  1. When you first choose AI practice without a saved key, a short setup appears with provider defaults already filled in. Paste your own key and continue; custom model and endpoint values are under Advanced. This saves settings only and does not call AI by itself. You can also configure or forget the key in Advanced → Learning.
  2. In Reader, start a reading of at least 80 characters, then choose AI practice. Before each live model request, inspect the exact learner data, provider/model and possible token cost, then agree to that request. Cached suggestions are labelled and do not make a provider call.
  3. Select a phrase with its source sentence, answer the situation, and review the quoted feedback. Accept useful feedback or mark it not useful before saving the phrase to Vault or trying another situation.
  4. Saving a phrase does not grade a review. Your regular FSRS reviews run locally. Previously cached phrase suggestions may be reused offline; new situations and feedback need your provider connection.
  5. Run the authored live AI evaluation cases to review correct use, a grammar error, an off-topic answer, and a missing required phrase. Each case requires separate consent; the exported report contains no API key and describes only those cases.
  6. Drafts and sessions are saved in this browser and included in study backups. Advanced → Learning lets you forget the key, clear phrase cache, or delete Tutor data. Browser data may be lost when cleared: export a backup first.

The offline tutorial is an authored walkthrough. It does not evaluate your answer or pretend to be a live model result. Browser speech recognition may also use your browser vendor's online service as described in pronunciation help.

More features & details
  1. Purpose: this app is a personal study & research tool — non-commercial, no account, no tracking. All dictionary data stays on your own device.
  2. Hear it, say it, see the IPA: 🔊 hears the word (browser text-to-speech); the pronunciation strip shows real IPA for most English words; 🎤 checks your pronunciation using your browser's speech recognition (Practice also has a say-it-aloud drill). On Chrome the audio is processed by Google, on Safari by Apple — this app has no server.
  3. Review reminders (optional): enable in ⚙ Advanced — local-only and opt-in: an app badge, a quiet banner, and notifications on installed Android/desktop PWAs at browser-chosen times. Nothing is sent anywhere.
  4. Bring your own dictionary file: open ⚙ Advanced in the top bar to load a .mdx/.mdd dictionary file you have the rights to use into either slot. The public edition ships with open-licensed dictionaries (WordNet 3.1, Simple English) by default — load commercial dictionaries such as OALD/LDOCE only if you own them. See the detailed guide + troubleshooting.
  5. Install on your phone:
    • iPhone / iPad (Safari): Share → Add to Home Screen.
    • Android (Chrome): menu ⋮ → Add to Home screen / Install app.
    Requires iOS 16.4+ (technical requirement: DecompressionStream).
  6. Deploy this app yourself: drag the folder onto Netlify Drop (free) or GitHub Pages. Publishing the app with only its open-licensed bundled data (WordNet 3.1, Simple English Wiktionary) is fine. ⚠️ If you or your group load commercial dictionary files (e.g. OALD/LDOCE), keep that deployment private — serving licensed content as a public service would be redistribution.
  7. Keyboard (desktop): ↑/↓ to pick a suggestion, Enter to search, Esc to hide.
  8. Reader mode: paste text or load a page and tap words to look them up; your saved sentence stays with the word — shown highlighted above the entry, with Add example for extra sentences.
  9. Vault & Review: every word, phrase and sentence lives in one place — notes, tags, status, search-within, multi-select. Review uses the FSRS spaced-repetition queue (know / forgot / skip).
  10. Your data is yours: export Vault items as JSON, or use the complete study backup to include local sessions and audio — no cloud, no account, nothing leaves your device.
  11. One-click EN–VI: add the open English–Vietnamese dictionary (OVDP, 386,600 entries) from the start screen or ⚙ Advanced.
  12. Practice & stats: 🎯 Practice (from Vault or Review) runs quick exercises — fill in the missing word, or listen & type — with Got it / Review again. 📊 Stats shows words learned, retention, due items and sources read.
  13. Export anywhere: the Vault exports your items as JSON, CSV, TSV or Anki-ready text, with field selection.
  14. Pronunciation: 🔊 speaks a word, 🐢 0.75× slows playback, and ↺ replays your saved sentence. IPA is shown when the dictionary data includes it.
  15. Look & language: switch theme (system / light / dark) with the 🌓 button; switch the navigation between English and Vietnamese with the EN/VI button.
  16. Find things again: 📊 Stats is in the top/bottom navigation; recent searches have their own page (View all from the Recent bar); 🏷️ Tags in the Vault renames or deletes a tag across every item.
  17. Install & offline safety: the ⬇ button installs the app; an “Offline” note appears if the network drops (your data keeps working). A JSON backup of your items is written on-device once a day — restore it from ⚙ Advanced.
Save words from any web page

Drag this button to your browser's bookmarks bar. Select text on any page, then click the bookmark to open it in Dual Dictionary's Reader.

📖 Send to Dual Dictionary

For a single word you can also open https://dualdictionary.netlify.app/?q=word — it searches right away.

Licenses & terms of use

This app is provided for personal study and research purposes only — non-commercial use. Dictionary files you load remain the property of their respective publishers (e.g. Oxford University Press, Pearson): use only files you are authorized to use, keep them on your own device, and do not redistribute them or serve them publicly.
Spoken audio uses your browser's built-in text-to-speech (no audio files bundled).

Advanced

Optional — most users never need this screen. Three tabs: your dictionaries, your data, and how the app behaves while you study.

Dictionaries in your slots

Slot 1

Slot 2

Slot 3 (optional — e.g. EN–VI)

Open dictionaries

Downloads the open EN–VI dictionary (OVDP, MIT) into Slot 2 — one-time, stored offline.

Loading a new .mdx replaces the one currently in that slot. Load from URL loads the whole set in one go: the matching .mdd (audio/images) and .css (stylesheet) sitting next to the .mdx on the server are fetched automatically. The file buttons are only for offline/manual completion. See the detailed loading guide + troubleshooting.

Read a YouTube video as text

On the video page, open the description → Show transcript, select all, copy, and paste it below. The video itself never plays in the app — you read the words and tap any word to look it up. A direct link fetch is impossible without a server (CORS), so this is one paste.

Listen & read along

Pick an audio file from this device and paste its transcript (YouTube copy, SRT/VTT or plain text). The audio plays locally — nothing is uploaded, and the session lasts until you close the page.