Written by the team that makes Stemmy. Every fact about the other four extensions comes from their own Chrome Web Store listing or pricing page, checked on 11 October 2026 and linked in the sources at the end. Prices and limits change, so check the source before you decide.
The short version, by need
Free tiers and prices below are as of 11 October 2026.
| Your need | Extension | Free tier | Paid plan |
|---|---|---|---|
| A quick definition, nothing more | Google Dictionary | Free | None listed |
| Learning another language while you browse | Toucan by Babbel | Free | None listed on the store page |
| Click-to-translate reading, with flashcards | Readlang | Free, with daily limits on phrases and AI explanations | From $6 a month or $48 a year |
| New words highlighted by level | Relingo | Free, up to 50 saved words | Premium; prices load with JavaScript and change with promotions, so check its pricing page |
| Meaning in your sentence, plus review | Stemmy | Free; AI meanings need a free account, with 150 free AI uses in total | No paid plan offered today |
What to look for in any vocabulary extension
Most people want two things: to understand the page in front of them, and to remember the word next week. Ask these questions before you install anything.
- Which direction are you learning? Some tools teach a new language to people who browse in their own. Others help people who already read English understand harder English.
- Does it fit the sentence? Many English words have several meanings. A meaning chosen for the sentence saves you sorting through them.
- Does it keep the context? A word saved with the sentence you found it in is easier to recall than a bare word.
- Is there a review step? Looking a word up once rarely makes it stick. Spaced review brings it back just before you forget it.
- What does the free tier really allow? Look for daily limits, total limits and caps on saved words.
For more on the habit itself, see how to remember new English words while reading online.
Quick definitions: Google Dictionary
Google Dictionary, by Google, shows a definition in a small pop-up when you double-click a word. A toolbar button gives the full entry for a word or phrase. If you opt in, it keeps a history of the words you looked up, which you can download as a CSV file. Foreign words are translated into the language you choose.
Suits: anyone who wants a fast definition and nothing else. The listing says other extensions can read your history, for example to make flashcards, but it describes no review mode of its own.
Price: free. Its store listing shows 4,000,000 users and a 3.8 out of 5 rating from 13.7K ratings, as of 23 October 2026.
Learning another language: Toucan by Babbel
Toucan works the other way round. On the sites you visit, it swaps some words and phrases into the language you are learning, so you meet them inside text you already understand. It also offers short phrase sets, practice sessions on some sites and a way to save words to review later. The listing names twelve languages, English among them.
Suits: people who browse mostly in their first language and want gentle, everyday exposure to a new one. It is less suited to understanding a hard English page you are reading right now.
Price: Toucan's website calls it a free extension, and its store listing does not show in-app purchases. The listing shows 200,000 users and a 3.5 out of 5 rating from 1.4K ratings, as of 23 October 2026. Toucan is also offered for Edge.
Translation-based reading: Readlang
Readlang's Web Reader lets you click a word, or drag across a phrase, to translate it on the page. Words you translate become flashcards and vocabulary lists. Its website lists more than 100 languages, AI explanations of words in context and apps for iOS and Android.
Suits: language learners who read a lot in their target language and like translation into their own.
Price: the free plan includes single-word translations without a cap, 10 phrase translations a day and 10 context explanations a day. Premium is $6 a month or $48 a year, and Premium Plus is $15 a month or $120 a year. The listing shows 100,000 users and a 4.3 out of 5 rating from 221 ratings. All as of 11 October 2026.
Level-based highlighting: Relingo
Relingo highlights and translates the words on a page that are likely new to you, based on a difficulty level you set and the words you have collected. Saved words go into a vocabulary book and come back in later reading, in flashcards and by email. It also adds bilingual subtitles to YouTube and other video sites. Its translations cover Chinese, Korean, Japanese, Spanish, Portuguese and French.
Suits: learners who want the page to show them which words to notice, and who also watch English video.
Price: the free version includes highlighting, translation, word training and a daily email, with up to 50 saved words and 50 saved examples. Premium removes the word cap and adds 10,000 monthly credits for paid translation engines, import and export, and Anki export. Credits can also be bought without Premium. The listing shows 40,000 users and a 4.6 out of 5 rating from 1K ratings, as of 11 October 2026. Relingo also offers Edge, Firefox, iOS and Android versions.
Context meaning plus review: Stemmy
Stemmy is the extension we make, for people who read English at work or for exams. Highlight a word, click the Stemmy button beside it or press Alt+Shift+D, and a Ghost Card shows the meaning that fits the sentence, the word's roots (WordDNA) and its pronunciation. AI meanings need a free account.
Save a word and it goes to your Vocabulary Wallet with its meaning, the source sentence and the page link. Reviews are short spaced-repetition sessions that cover only the words that are due. X-Ray scans a difficult page and shows which words are worth learning. You can also turn on Immersion, which shows your saved words again on pages you read.
Suits: people who read English and want each word explained in its sentence, then reviewed.
Price: Free to install. No paid plan is offered today. AI features need a free account (Google Sign-In or email). Each account gets 150 free AI uses in total, once; Ghost Card lookups and cloud voice draw on them. Once the included uses are spent, your wallet, reviews, the toolbar badge and export keep working, and looking up a word you already saved stays free; new AI meanings wait for a future allowance. Questions: hello@stemmy.app.
Where others do more: Stemmy is built for Chrome only and does not teach other languages. Toucan is also offered for Edge, Readlang lists iOS and Android apps, and Relingo lists Edge, Firefox, iOS and Android versions as well as video subtitles.
How to choose
- You only want to understand the word and move on. Google Dictionary is enough.
- You are learning Spanish, French or another language. Try Toucan for passive exposure, or Readlang if you read a lot in that language.
- You want the page to point out new words for you. Relingo highlights by level. Stemmy's X-Ray does a similar job on a page you choose to scan.
- You read English at work or for exams and want words to stick. Look for a meaning that fits the sentence, a saved example and spaced review. That is what Stemmy is built for; see how the Stemmy app works and flashcards from your reading.
Frequently asked questions
Which Chrome extension is good for learning English vocabulary?
It depends on your need. For a quick definition, Google Dictionary is free and does that one job. For level-based highlighting, try Relingo. For the meaning in your sentence plus spaced review, try Stemmy, whose AI meanings need a free account.
Are these extensions free?
All five are free to install as of 11 October 2026. Readlang's free plan has daily limits on phrases and AI explanations, Relingo's free version caps saved words at 50, and Stemmy gives each free account 150 AI uses in total.
Do I need an account to use Stemmy?
Stemmy is free to install, and your wallet is stored in your browser. AI features, including Ghost Card meanings, need a free account (Google Sign-In or email), and each account gets 150 free AI uses in total, once.
Who wrote this comparison?
The team that makes Stemmy. Facts about the other extensions come from their own store listings and pricing pages, linked in the sources with the date we checked them.
Sources
- Google Dictionary (by Google), Chrome Web Store listing: chromewebstore.google.com/detail/google-dictionary-by-goog/mgijmajocgfcbeboacabfgobmjgjcoja, checked 11 October 2026.
- Toucan by Babbel, Chrome Web Store listing: chromewebstore.google.com/detail/toucan-language-learning/lokjgaehpcnlmkebpmjiofccpklbmoci, checked 11 October 2026.
- Toucan website: jointoucan.com, checked 11 October 2026.
- Readlang Web Reader, Chrome Web Store listing: chromewebstore.google.com/detail/odpdkefpnfejbfnmdilmfhephfffmfoh, checked 11 October 2026.
- Readlang website and pricing: readlang.com, checked 11 October 2026.
- Relingo, Chrome Web Store listing: chromewebstore.google.com/detail/dpphkcfmnbkdpmgneljgdhfnccnhmfig, checked 11 October 2026.
- Relingo pricing: relingo.net/en/pricing, checked 11 October 2026.
- Stemmy: this site and the Stemmy privacy page.