Chrome Extension That Defines Highlighted Words

Highlight any word, get an instant tooltip with definition, examples, and etymology.

research-learningbeginner#dictionary#language#reading
PlugThis prompt
Build a Chrome extension called "Dictionary on Highlight" that defines words when the user highlights them. The extension should: (1) detect text selection on any webpage via a content script, (2) when a single word is selected (no spaces), show a small tooltip near the selection with the word's definition fetched from the free Dictionary API (https://api.dictionaryapi.dev/), (3) include in the tooltip: pronunciation (audio play button), definition, part of speech, example sentence, etymology if available, (4) include an options page where the user can disable the extension on specific sites or set a minimum word length, (5) cache definitions in chrome.storage for offline access. Permissions: storage, activeTab. Host permissions: <all_urls>, https://api.dictionaryapi.dev/*. Manifest V3.

What this extension does

Shows a tooltip with the definition, pronunciation, examples, and etymology when the user highlights a single word on any webpage. Uses the free Dictionary API. Caches definitions for offline reuse.

How it works

A content script listens for selectionchange events. When a single word is selected, the script fetches the definition from the Dictionary API (free, no key required) and renders it in a tooltip with shadow DOM. Cached results in chrome.storage avoid duplicate API calls.

Permissions used: storage, activeTab

Host permissions: <all_urls>, https://api.dictionaryapi.dev/*

Who builds this

For ESL learners, vocabulary builders, students reading academic content, and anyone who frequently encounters unfamiliar words while browsing.

How to build it in 3 minutes

  1. Sign in to PlugThis and open the chat input.
  2. Copy the prompt above and paste it into the chat.
  3. PlugThis generates the full Manifest V3 extension in 60-90 seconds.
  4. Download the zip, extract it, and load it via chrome://extensions developer mode.

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Build it now, free.

Paste the prompt above into PlugThis and ship your extension in 3 minutes.