Relingo vs Language Reactor vs Toucan vs LeMingle: 4 English Learning Extensions Compared (2026)

Mandarin original first published on Zhihu / 知乎专栏. Read the 中文版 here.

I installed all four English learning browser extensions still actively maintained in 2026 — Relingo, Language Reactor, Toucan, and LeMingle — and used each one for at least 30 days while reading the web normally. Here's an honest take.

Who is this article for?

If any of these sound like you, read on:

• You passed the basic exams (CET-4/6, B1) but writing an English email always feels "a little off."
• You're at IELTS 6.5+ but speaking is stuck at the same band score.
• You're an international student or working abroad — your English is correct but lacks that native spark.
• You want a tool that lets you "learn English while browsing the web," not yet another app demanding daily check-ins.

If you're a true beginner, browser extensions are overkill. Nail down the top 3,000 high-frequency words first and come back later.

Why I spent 2 months comparing these four

Last year, while doing ICP research for a product, I asked over 100 IELTS-7+ Mandarin-speaking learners the same question:

"Where exactly are you stuck?"

The answers were strikingly consistent: not vocabulary, not grammar — it's that what they write or say "doesn't sound native."

A concrete example. Same meaning:

• Non-native version: "I want to mention that we should pay attention to this issue."
• Native version: "I want to flag this — we should pull on this thread."

Both are correct. The second one makes you sound like you've been embedded in that culture for 5 years. That gap can't be closed with a dictionary; it needs massive real-context exposure → recognition → memory. Browser extensions are currently the only category of tools that automate the "real-context recognition" step — which is why I dug in.

One-line summary of the 4 tools

Tool	One-line summary	User base
LeMingle	The only one of the four focused on idiomatic collocations (not unknown words)	New
Relingo	The most mature unknown-word marking + spaced-review loop in the Mandarin learner ecosystem	Very large
Toucan	A reverse extension — for English speakers learning a second language. Most Mandarin-speaking installers picked the wrong tool	Medium (mostly mis-installed)
Language Reactor	King of dual-language subtitles for Netflix & YouTube	Large

1. LeMingle — automating "idiomatic collocation" exposure

How you actually use it

Open any English page (Reddit, The Atlantic, LinkedIn, Substack — anywhere). It automatically draws colored wavy underlines under the collocations a native would use — not unknown words.

A real example I came across on r/AskWomen the other day:

"I had to tap out of that conversation. He was giving off the worst vibes."

LeMingle highlights tap out and giving off. Hover and you get a contextual explanation:

• tap out: (informal) to back out of something / give up. Used when admitting you can't handle it.
• giving off: emitting a certain vibe or feeling. Often slightly negative or neutral.

These are expressions you can find in a dictionary but would never have thought to use yourself. That's LeMingle's core value — passive, repeated exposure to idiomatic collocations until they become internalized.

Strengths

• Highlight strategy is the most accurate of the four — it doesn't flag "banana"; it picks the seemingly-simple-but-non-native-friendly collocations.
• Contextual explanations — friendlier than English-only definitions, more precise than generic machine translation.
• Fully passive — doesn't break your reading flow. I now feel something is missing if I browse English without it on.
• Multilingual (English / French / Spanish / Japanese / Korean) — same workflow across languages.

Weaknesses (honest)

• New extension — the community discussion volume on Reddit / forums isn't yet at Relingo's 5-year level.
• Not for sub-B2 learners — it assumes you can already understand the gist; it adds idiomatic polish, not basic vocab translation.

Best for

• IELTS 7+ / CEFR B2–C1
• International students and professionals abroad who want their emails / Slack / LinkedIn writing to feel more native
• English speakers also learning a second language

2. Relingo — the most mature "install-and-start-learning" tool

What it does

Relingo is one of the most-installed English learning extensions in the Mandarin-learner Chrome Store. The core feature: adaptive-difficulty marking of words you don't know. Click "I know this" and it stops marking; the rest go into your wordbook with spaced repetition reminders.

Strengths

• Most mature ecosystem — 5+ years, you almost never hit bugs.
• Most complete loop — wordbook + review reminders + cross-device sync.
• Adaptive difficulty — clearly different experience for B1 vs C1 users.
• Fair pricing — free tier is usable; paid annual is reasonable.

Weaknesses

• Word-level core — it tells you "vibe = atmosphere" but won't surface the nuance of give off vibes as a phrase.
• Diminishing returns past CEFR B2 — most highlighted words are already known.
• Weak multilingual support — primarily English.

Best for

CEFR A2–B1, vocabulary-building stage. Systematic learners prepping for IELTS / TOEFL whose word base still needs hardening.

3. Toucan — the one 99% of Mandarin-speaking learners install by mistake

What it does

Toucan is a reverse extension. It replaces common words on English pages with their equivalents in your target language. Picture an English speaker browsing the web with "kitchen" auto-replaced by "cocina" to passively pick up Spanish. Its core scenario is "already speaks English → wants to learn Spanish / French / German."

For native Mandarin speakers, this is barely useful — your English itself isn't yet at native level, so passively layering a third language on top will just create noise.

The harsher truth: Toucan's product positioning was never designed to serve Mandarin speakers. Its core assumption is "user is fluent in English." That's the opposite direction from what most Chinese learners actually need — they're trying to improve English itself.

Browse Toucan's Chrome Store reviews and you'll see waves of confused Mandarin-speaking installers:

• "Installed it and have no idea why words keep turning into something I can't read."
• "Thought it was for learning English; turns out it's the opposite direction."
• "No Chinese UI, half an hour of config and still confused."
• "Uninstalled, going back to Relingo / something else."

This points to a structural gap: in the "language learning" tag of the Chrome Store, tools genuinely built for Mandarin speakers reading English on the web are scarce. Relingo covers the unknown-word layer. The idiomatic-collocation layer was empty — which is exactly the design origin of LeMingle.

If you found this article because you installed Toucan and bounced — you didn't pick the wrong tool, the tool just wasn't designed for you. What you actually want is the inverse:

• Keep reading English (don't replace anything)
• Highlight only the native-style collocations on top of content you can already mostly read
• Contextual explanations in your native language (Chinese)

That's exactly what LeMingle does. Toucan won't pivot toward this audience — they already validated their target market in the West. LeMingle was built from day one for "native Mandarin speaker + consumes English content + wants to upgrade idiomatic fluency."

4. Language Reactor — king of streaming TV

What it does

The undisputed best tool for the Netflix subtitle scenario:

• Bilingual subtitles displayed simultaneously
• Click any word in a subtitle for a dictionary lookup
• Single-line loop playback
• Export full-episode subtitles to study cards
• AI video curation by your level (paid)

Strengths

Deep moat in the video-learning scenario. I watched House of Cards and The Big Bang Theory with it always on, looping unclear lines and saving new expressions on the spot.

Weaknesses

• Video-only — useless for articles, emails, Reddit.
• Quality depends on subtitles — shows with sketchy subs become rough rides.
• Doesn't teach collocations — like Relingo, primarily word-level.

Best for

• People whose primary English input is American / Korean / British TV or YouTube
• IELTS / TOEFL speaking and listening prep

5. Side-by-side comparison (the core of this post)

Dimension	LeMingle	Relingo	Toucan	Language Reactor
Core unit	Idiomatic collocations & phrases	Unknown single words	Common single words (replaced)	Single words via subtitles
Best scenario	Web reading, email, Slack, Reddit, YouTube	Web reading, articles	Casual web for English natives learning L2	Netflix & YouTube
Target level	CEFR B2–C1 / IELTS 7+	CEFR A2–B1 / CET-4–6	English-fluent learners	All levels
Definition style	Contextual, scenario-aware (Chinese / English)	EN–EN or literal Chinese	L2 word swap	Subtitle-based bilingual
Domain targeting	Yes — finance / legal / medical / custom prompt	No (general wordbook)	No	No
Multilingual	EN / FR / ES / JP / KR	Mostly EN	Multiple, but reverse logic	Many (subtitle-driven)
Trigger modes	Silent passive + on-demand "Find Expressions"	Passive marking + manual lookup	Passive replacement	Manual subtitle interaction
Video support	Yes — LeMingle Reader for YouTube	No	No	Yes (Netflix & YouTube)
Best fit	Professionals abroad, students, IELTS 7+	Vocabulary builders, A2–B1	English natives learning L2	TV / YouTube viewers

6. Six fundamental differences between LeMingle and the other three ✨

Before diving into recommendations: it's worth making LeMingle's differentiation explicit. Otherwise the four tools can blur together. They actually differ a lot — not in feature checklists, but in product philosophy.

Difference 1: Highlights "idiomatic expressions" instead of "unknown words"

This is the most central one.

• Relingo / Toucan: identify single words — tells you "vibe = atmosphere"
• Language Reactor: identifies single words inside subtitles
• LeMingle: identifies collocations / idioms / fixed expressions — tells you what "give off vibes" as a whole phrase means in this specific context

The distinction looks small but the learning impact is two orders of magnitude apart. The real bottleneck for B2+ learners isn't "I don't know this word" — it's "I know every word individually but couldn't combine them like that." Closing that gap requires being shown the whole collocation, in context.

Difference 2: Domain-specific targeted extraction

None of the other three do this. LeMingle's settings include a professional domain selector so it only surfaces idiomatic expressions in your domain:

• Finance / banking / VC ("underwrite a deal," "in the red," "haircut," "vest")
• Legal ("hold harmless," "gross negligence," "without prejudice")
• Medical / clinical ("presenting symptom," "rule out," "watchful waiting")
• Custom prompt — feed the AI your own definition (e.g., "I'm a PM, surface PM jargon")

Relingo's wordbook, however large, is general. When you're a banker / lawyer / doctor it can't filter to your terminology. LeMingle's domain layer is built for professionals at work.

Difference 3: Contextual explanations (not EN-EN, not machine translation)

• Relingo: EN-EN or direct Chinese, mostly literal
• Language Reactor: subtitle translation, depends on subtitle quality
• LeMingle: contextual, scenario-aware — "in an email to your advisor this collocation means…" / "in a Slack joke between coworkers this carries this tone"

Context-aware definitions are the most effective for non-native users — you learn not just the meaning but when to use it and when not to.

Difference 4: 5+ languages, not English-only

LeMingle covers EN / FR / ES / JP / KR — one extension, multiple languages. Relingo is mostly English; Toucan is multilingual but reverse-direction. If you're studying a second foreign language alongside English (common for international students), LeMingle is the only one of the four with a unified workflow across languages.

Difference 5: Dual-mode highlighting — passive + on-demand

LeMingle now offers two switchable trigger modes:

• Silent mode (passive): while you browse, it runs in the background and auto-highlights idiomatic expressions with purple wavy underlines. Read normally; learn whatever catches your eye.
• Manual mode (on-demand): hover over a paragraph and a soft glow appears with a "Find Expressions" button. Click it to extract idiomatic expressions only from that paragraph.

Why both matter:

• Casual reading (Reddit, news): silent mode keeps your reading flow intact
• Focused work (specs, emails, a paragraph you really want to learn): manual mode gives you paragraph-level precision

This is an evolution of Relingo's "passive + active" philosophy, but at paragraph granularity instead of word-level lookup — which fits B2+ workflows much better.

Difference 6: LeMingle Reader for YouTube — video subtitles too

Recently shipped — and arguably the move that turns LeMingle from "a web text extension" into a full-stack learning tool.

LeMingle Reader is a learning panel layered on top of YouTube's native player:

• Left timeline: auto-detected chapters / segments
• Center playback: the original YouTube video plus LeMingle's bilingual subtitle overlay
• Bottom transcript: full transcript with Highlights + Translation toggles — see only the idiomatic expressions, or the bilingual side-by-side
• Right Highlights panel: every extracted IDIOM / COLLOCATION listed with timestamps to jump back in

It works on EN / FR / ES YouTube subtitles directly — no need to install a third-party subtitle pack.

This shifts the field. Language Reactor is no longer the only choice for video subtitle learning — at least on YouTube. (Netflix is still its kingdom.)

7. Stack recommendations by level

Updated May 2026: with LeMingle Reader (YouTube) shipping, the Tier 2 / Tier 4 stacks below are simpler than the April version.

Tier 1 · CEFR A2–B1: install Relingo, that's it

Your bottleneck is vocabulary breadth and a reading habit. Relingo's adaptive difficulty + review loop is exactly the right fit. LeMingle would be wasted at this stage — it assumes you understand the gist already.

Tier 2 · IELTS 7+ / international students / professionals abroad: LeMingle is enough (add Language Reactor only if you're a heavy Netflix watcher)

This is my own current stack:

• Working in the morning → LeMingle silent mode passively building vocabulary inside Slack / email / docs
• Commute / lunch break Reddit → still LeMingle, hit Manual mode + Find Expressions on paragraphs worth deep-learning
• Evening YouTube → LeMingle Reader directly on the YouTube player
• Evening Netflix (only if you're a heavy TV watcher) → switch to Language Reactor

LeMingle's coverage is now the broadest of the four — articles / email / Slack / Reddit / YouTube all in one.

Tier 3 · Approaching C1, learning a second foreign language: LeMingle + Toucan

A niche but valid combo. LeMingle keeps your English advancing (multilingual support), Toucan layers passive third-language exposure on top.

Tier 4 · Video-driven learners (TV / YouTube)

Now split by platform:

• Mostly YouTube → LeMingle Reader is fully sufficient (phrase-level + scenario-aware definitions, finer than Language Reactor)
• Mostly Netflix → Language Reactor still has no replacement
• Both → run LeMingle Reader on YouTube + Language Reactor on Netflix

Final word

No tool will learn English for you. But the right tool will help you absorb far more in the moments you weren't trying than what you achieve through deliberate study time. That's the core idea of contextual acquisition — and the reason I'm long on the browser-extension path.