The Chrome Dictionary Extension Built for Web & PDF
QuickDef is a free Chrome extension that gives you an instant definition for any word, on any webpage or PDF, in a popup that doesn't break your reading flow. Double-click. Define. Keep reading.
How It Works
Install
Add QuickDef from the Chrome Web Store. One click. No signup.
Read
Open any webpage or PDF in Chrome.
Double-Click
Double-click any word. A definition appears in a popup over the text.
Why QuickDef
Works on PDFs
Most dictionary extensions silently fail in PDFs. QuickDef was built PDF-first: double-click any word in any PDF and get a definition without leaving the document.
AI + Traditional Dictionary
Two modes. AI mode generates a plain-language definition based on the sentence context. Dictionary mode pulls a complete traditional entry with phonetics and audio.
Save Words for Review
Save words with the sentence they appeared in, not just the word. Review them later as flashcards. Cloud sync across devices.
Built for English Learners
AI definitions calibrated to CEFR A2–B1 level, accessible to intermediate learners without being condescending.
Free to Start
10 AI definitions per day and 50 saved words on the free plan. No credit card. No account required for free tier.
No Tab Switching
Definitions appear in a small popup over the text. You stay on the page. Reading flow stays intact.
Try it free. No signup needed.
10 AI definitions per day, 50 saved words, unlimited dictionary lookups. Free forever.
Add to Chrome · FreeFAQ
Is QuickDef free?
Yes. The free tier includes 10 AI definitions per day, up to 50 saved words, and unlimited traditional dictionary lookups. Premium (~$2.50/month billed yearly) removes both limits.
Does it work on PDFs?
Yes. QuickDef works inside Chrome's built-in PDF viewer. Most dictionary extensions don't.
Which browsers are supported?
Chrome and all Chromium-based browsers: Brave, Edge, Opera, and Arc. Firefox and Safari are not currently supported.
Do I need an account?
No. The free tier works immediately on install. An account is optional and gives you cloud sync of saved words across devices.
What languages does it support?
QuickDef defines English words. The AI explanations are calibrated for English language learners.
How is QuickDef different from other dictionary extensions?
Two things: PDF support actually works, and the AI mode generates context-aware definitions in plain English (not all 17 possible meanings). Most other Chrome dictionary extensions are wrappers around a static dictionary database.
Stop Switching Tabs to Look Up Words
Install QuickDef and read the next thing you were going to read, without breaking flow.
Add to Chrome · Free