Does Toucan support Vietnamese?

No. Vietnamese is not on Toucan's language list. The bigger issue is direction. Toucan assumes you are reading a page in a language you already know and swaps a few words into the language you are learning. A Vietnamese speaker learning English needs the opposite.
If you searched this because you installed Toucan and could not find Vietnamese in the dropdown, the answer is in the block above. What follows is the part that took me longer to work out, and the reason I ended up writing my own extension instead of waiting for an update.
Is Vietnamese on Toucan's language list?
It is not. Toucan's published list covers Spanish, French, German, Italian, Portuguese, Japanese, Korean, Hindi, Hebrew, Arabic, Chinese and English. Vietnamese does not appear on it.
Toucan is owned by Babbel now, so the authoritative place to check is the Babbel help centre or the extension's own Chrome Web Store description. Any list in a blog post, including this one, goes stale the moment a company ships a new language.
TODO_STAT — Confirm the supported base language list specifically, not the list of languages you can learn. The primary pages were unreachable when I wrote this; two secondary sources agreed, but a first-party citation would be better.
Why is the language list the smaller problem?
Because Toucan translates in one direction, and adding a language name would not change that direction. Toucan assumes the page in front of you is written in a language you already read comfortably, and it swaps a handful of those words into the language you are studying.
For Toucan's core user that means an English-language page and a Spanish word appearing in it. You read a news article, bread comes out as pan, and one word lands.
Now invert every part of that. The pages a Vietnamese reader opens all day are VnExpress, Tuổi Trẻ, Vietnamese Wikipedia, Vietnamese Facebook. The language they want is English. So the swap has to run from Vietnamese into English, on a Vietnamese page.
That is not one missing menu item. It is a different product.
Can I just set English as the language to learn?
You can select it, but it will not do what you want. English is on Toucan's list of languages you can learn. The catch is that the page you are reading has to be in a language Toucan handles as your base, and Vietnamese is not one of them.
Which means the only way to make Toucan swap words for you is to already be reading the web in English. If you can comfortably read a full English page, your vocabulary problem has moved on to something else.
I mention this because several Vietnamese-language write-ups about Toucan skip it. They list the features, praise the idea, and leave the reader to discover after installing that there is nothing for them to select. The idea genuinely is good. It was just not built for this reader.
So what should a Vietnamese learner use instead?
Something that runs Vietnamese to English. It has to read a Vietnamese page, choose a few words worth replacing, and drop an English word in their place without wrecking the sentence.
That is what I built, and I built it because I could not find one. I am a student in Ho Chi Minh City, and I quit every vocabulary app I ever downloaded. Not because they were bad. Because all of them needed me to open them first.
Merid runs on the page you already have open. Here is Vietnamese Wikipedia, with kết hợp replaced by amalgamate.

How is Merid actually different?
Three ways: the direction of the swap, the word lists, and where the work happens. Toucan serves English speakers learning something else. Merid serves Vietnamese speakers learning English. Everything else follows from that.
| Toucan | Merid | |
|---|---|---|
| Swap direction | Page language into your target language | Vietnamese into English |
| Pages it works on | Pages in a language Toucan supports | Vietnamese pages you read anyway |
| Word lists | Toucan's own levels | SAT, C1, C2, or a list you build |
| Where it runs | Per Toucan's description | Word replacement happens on your machine |
| Price | Free tier plus paid plans | Free |
Merid ships three lists, SAT, C1 and C2. I picked those three because they are the three targets the people around me are actually aiming at, not because they were the easiest to assemble.
The part I am most attached to is the context check. Merid can ask a model whether the word it just swapped in genuinely fits the sentence it landed in. Below, it caught itself: it had used amorous in a post about Messi and Ronaldo, decided that was wrong, and replaced it with captivate.

Anything worth keeping goes to your deck with one click. That screenshot is my own deck as it stood: twenty-five words, fifteen still in progress, ten marked known.

Is it worth waiting for Toucan to add Vietnamese?
If you are learning Spanish or Japanese and you browse in English, do not wait for anything. Toucan works today and does its job well. This post is not an argument that Toucan is bad.
If you are Vietnamese and you want more English vocabulary while reading Vietnamese news, waiting for a name to appear in a dropdown will not help. The thing that needs to change is not the list, it is the direction. That has to be built from scratch, which is the part I already did.
Frequently asked questions
- Is Toucan free?
- Toucan has a free tier and a paid one. Check their site directly, since tier limits and pricing change and I am not going to quote numbers I cannot verify.
- What if Toucan adds Vietnamese later?
- It would depend entirely on which role they add it in. Adding Vietnamese as a language you can learn is a different feature from supporting Vietnamese pages as the base language you read in.
- I am learning Japanese. Should I use Toucan?
- Yes, if you browse in English. That is exactly what Toucan is built for, and it does it well. Merid is not a replacement for that use case.
Try Merid on the page you are reading
Merid swaps a few words on the pages you already open for English vocabulary worth knowing. Free, and it runs on your own machine.