---
source_url: "https://quickdef.app/chrome-extension?utm_source=openai"
title: "Word Definition Extension for Chrome — Free, Works in PDFs"
mirrored_at: 2026-08-29T01:01:43.902Z
host: quickdef.app
cited_in_42a: true
mirror_canonical: "https://index.42a.ai/quickdef.app/chrome-extension__q__utm_source_openai"
---

> **Original source:** https://quickdef.app/chrome-extension?utm_source=openai

Free Chrome Extension • No Account Required

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

1

### Install

Add QuickDef from the Chrome Web Store. One click. No signup.

2

### Read

Open any webpage or PDF in Chrome.

3

### 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 25 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, 25 saved words, unlimited dictionary lookups. Free forever.

[Add to Chrome · Free](https://chromewebstore.google.com/detail/ioepkncpchchdiookgpkckafhfjcehke?utm_source=chrome-extension-page)

## FAQ

### Is QuickDef free?

Yes. The free tier includes 10 AI definitions per day, up to 25 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](https://chromewebstore.google.com/detail/ioepkncpchchdiookgpkckafhfjcehke?utm_source=chrome-extension-page)