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Definer Chrome extension

Definer lets you highlight a word or phrase on any webpage and instantly get a definition, translation, or AI-generated explanation in a popup. It's best for readers, language learners, and researchers who don't want to switch tabs to look things up. The catch: AI explanations depend on an underlying AI service, which may have usage limits.

  • PriceFreemium
  • CategoryEducation
  • Works inChrome, Edge, Brave (desktop)
  • ✓AI-powered

Last checked against the Chrome Web Store listing · Independent, not affiliated with Google

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Pros

  • works by simply selecting text on any webpage
  • combines definitions, translation, and AI explanations in one tool
  • supports PDFs and EPUBs in addition to regular webpages
  • saves time compared to searching separately for each lookup

Cons

  • AI explanation quality depends on the underlying AI model used
  • translation accuracy can vary by language pair
  • some AI features may require an account or have usage limits

Best for

  • looking up word definitions without leaving the page
  • translating unfamiliar words or phrases while reading
  • language learners who read foreign-language content
  • getting quick AI explanations of confusing text

Skip it if

  • users who need in-depth dictionary etymology or academic references
  • reading in offline PDFs where selection may behave differently than on web pages

Key features

  • select-to-define popup on any webpage
  • built-in word translator for multiple languages
  • AI-powered explanations for selected text
  • works across webpages, PDFs, and EPUBs

What Definer does

Definer adds a select-and-look-up feature to your browser: highlight any word or phrase on a webpage, PDF, or EPUB, and it shows a definition, translation, or AI-generated explanation in a small popup. This saves you from opening a separate dictionary or translation site every time you hit an unfamiliar term while reading.

Definer free vs paid

Definer's core select-to-define and translation features are available for everyday use. AI-powered explanations may rely on a connected AI service, which can come with usage limits or a paid tier for heavier use. Check the Chrome Web Store listing for the current breakdown of free versus paid functionality.

Is Definer safe?

Definer needs access to webpage content to detect and process the text you select, since that's how it generates definitions and translations. If it offers AI explanations, selected text may be sent to an AI service to generate a response. Review the permissions and any privacy details before using it on sensitive documents.

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Definer: FAQs

Is Definer free?

Definer's core lookup and translation features are available for free; AI explanation features may have usage limits or a paid tier.

Is Definer safe to use?

It needs access to page content to read selected text, and AI features may send that text to an AI service for a response.

How do I use the Definer extension?

Install it, highlight a word or phrase on any webpage, and a popup will show a definition, translation, or AI explanation.

What are Definer alternatives?

Other select-to-define extensions and browser or OS built-in dictionary tools are common alternatives.

Does Definer work on PDFs?

Yes, Definer is built to work on PDFs and EPUBs in addition to regular webpages.

Can Definer translate between any two languages?

Language support depends on the translation engine Definer uses; check its settings for the list of supported languages.

How does Definer's AI explanation feature work?

When you select text and choose the AI option, Definer sends the selection to an AI service to generate a plain-language explanation.

Why isn't the Definer popup appearing?

Some websites restrict text selection behavior or scripts, which can prevent the popup from showing; try reloading the page.

Does Definer store what I look up?

This depends on the extension's privacy practices; check its listing or privacy policy for details on data handling.

Can Definer be used for language learning?

Yes, its combination of definitions, translation, and AI explanations makes it useful for looking up unfamiliar words while reading in another language.