In the i18n world, Pseudo Loc Test is one of the early stage methods that gives some benefits. 

  1. Detecting hard coded strings
  2. Testing flexibility of UI components like button labels
  3. Suitability of using multiple languages(include Asian languages) for fonts.
  4. Testing i18n related functions(if those are already developed) – Date formatter & number formatter 

With the ECMAScript 6, we already have a good number of npm packages that we can simply install and initiate on our applications. Most of them support the Latin 1 & 2 character set, but not many packages support Asian characters and Latin Extended-A(0100-017F) all together.

So, here I simply create my own PL Test package – i18next-pseudoloc

By using the i18next-pseudoloc, developers can test Latin Extended-A & limited Korean/Japanese/Thai. Most Asian characters, I have picked above 2 bytes characters.


$ npm i i18next-pseudoloc


import i18n from "i18next";
import { initReactI18next } from "react-i18next";
import PseudoLoc from 'i18next-pseudoloc';
  .use(new PseudoLoc({
    enabled: true,
    enableCJK: true,
    sourceLocale: 'pt-BR', // pt-BR is only for PL Test
    postProcess: ["pseudoloc"],

How to ready Pseudo Loc string

<긇<[Ŷṓṵ āŗė ėňḡĩňėėŗ, ŧĥėň ĉĥėĉķṓṵŧ ŧĥė ŗėṗṓ ṓϝ ŧĥĩş āṗṗḽĩĉāŧĩṓň。]>ヲ>
  • There are Latin character sentence opening and closing markers – <[ and ]>
  • There are Korean/Japanese/Thai opening and closing markers with random characters – <긇 and ヲ>
  • If the sentence has the .(period – fullstop), then it will be replaced with Japanese period – 
  • If the sentence has the ?, then it will be replaced with Spanish inverted mark of interrogation – ¿
  • If the sentence has the ,(opening quotation), then it will be replaced with the German opening quotation – 
  • So, if you see <<[ or ]>>, this indicates the font in a product is not supporting Asian characters(even the fallback is failing).

In the modern web, with the rise of Google Font, most modern websites support a wide range of Unicode and have well-implemented glyph fallback mechanisms. However, there are still systems that do not support fonts for specific languages. For instance, mobile phone operating systems built for a limited market may not include an entire font set for non-target market languages. Therefore, the importance of performing PL (language) tests in the early stages of i18n is still significant.




I am a software engineer who enjoys building things. Please share your interest with me – chrisyoum[at]gmail.com