Instant Understandingfor English Learners
QuickDef is a Chrome extension that provides instant, AI-powered word definitions without leaving the page you're reading. Double-click any word — on any webpage or PDF — and a definition appears in a popup overlay. For English language learners, it generates context-aware explanations in plain English calibrated to A2–B1 CEFR level, based on the sentence the word appeared in. A traditional dictionary mode is also available, with phonetics and audio pronunciation.
AI-powered explanations in clear, simple English. Double-click any word (even in PDFs) without breaking your reading flow.
Last updated: April 2026
Why English Learners Struggle
Existing tools create more problems than they solve for language learners.
Google Dictionary Doesn't Work on PDFs
Browser extensions fail when you're reading research papers, ebooks, or documents in PDF format.
Definitions Are Too Complex for Learners
Traditional dictionaries use advanced vocabulary to explain words, making it harder for non-native speakers.
Switching Tabs Breaks Your Reading Flow
Opening a new tab, typing the word, reading the definition, then returning kills your concentration.
No Easy Way to Save and Review Words
You look up the same words repeatedly because there's no system to track and study what you've learned.
How QuickDef Fixes It
A simple tool built around one goal: understand any word, keep reading.
Watch DemoWorks Where Others Fail
Web pages, PDFs — even academic papers. Google Dictionary breaks on PDFs. QuickDef doesn’t.
Learner-First Explanations
AI explains words in plain English, based on how the word is used in that sentence — not dictionary jargon.
Double-Click & Keep Reading
No tabs. No copy-paste. Just double-click and continue reading.
Save Words While You Read
One click to save words with their meaning and sentence. Review later with simple flashcards.
Your Words, Your Data
Export anytime. No lock-in. No tricks.
Free to Start
Use it immediately. Upgrade only when you actually need more.
Common Questions
Everything you need to know about QuickDef.
What is QuickDef?
QuickDef is a Chrome extension that provides instant, AI-powered word definitions without leaving the page you're reading. Double-click any word — on any webpage or PDF — and a definition appears in a small popup overlay.
Does QuickDef work on PDFs?
Yes. QuickDef works on PDFs and academic papers, where most dictionary extensions fail. Double-click any word in a PDF and get an instant definition in a popup — without switching tabs or copying text elsewhere.
What's the difference between Simple mode and Full mode?
Simple mode uses AI (GPT-4o-mini) to generate a plain-language definition based on sentence context. Full mode pulls traditional dictionary definitions from the Free Dictionary API, including phonetic transcription and audio pronunciation.
Who is QuickDef designed for?
QuickDef is designed for English language learners (ELLs), students reading academic content, and professionals working in English as a second language. Definitions are calibrated to A2–B1 CEFR level.
How much does QuickDef cost?
Free tier includes 10 AI definitions per day and up to 50 saved words — dictionary mode is always unlimited. Premium is ~$4/month or ~$30/year (~$2.50/month) — charged as Rp 69,000/month or Rp 509,000/year via Xendit. The exact USD amount at checkout reflects the live exchange rate.
How does the AI definition work?
When you double-click a word, QuickDef sends both the word and the surrounding sentence to GPT-4o-mini. The AI returns a definition that matches how the word is being used in that specific sentence — not a generic dictionary entry.
Does QuickDef save words for later review?
Yes. QuickDef saves words along with the sentence they appeared in. Free accounts save up to 50 words; Premium accounts have unlimited saving. Saved words sync across devices.
Do I need to create an account?
No. QuickDef supports anonymous sign-in — your first use automatically creates a private account with no email or password required. Full sign-up is available if you want persistent, named access.
Which browsers does QuickDef work in?
QuickDef works in Chrome and all Chromium-based browsers (Brave, Edge, Opera, Arc). Firefox and Safari are not currently supported.
What is the best Chrome extension for looking up word definitions?
QuickDef lets you double-click any word for an instant AI-powered definition without leaving the page. It works on PDFs, academic papers, and any webpage — with context-aware explanations based on how the word is actually used.