Try them here, for Firefox and Chrome:
https://chrome.google.com/webstore/detail/glish/jfheijenmheiialipkmahkhcdmfefclb/
https://addons.mozilla.org/en-US/firefox/addon/glish/
Translate random common words within your webpages to a language of your choice. Learn foreign vocab in the context of an English sentence. Choose the language and the quantity of translated words. As you get more familiar with the vocab lists, you can increase the variety of words translated. This app is intended for people who'd like to expose themselves to foreign vocabulary, but aren't sufficiently knowledgable to read foreign websites. Do not learn grammar from this app. The words are translated directly and often incorrectly. Use this app as a type of flashcard practice to adjust to foreign words in the context of an understood sentence.
Available languages are:
arabic ar
armenian hy
chinese zh
czech cs
esperanto eo
estonian et
finnish fi
french fr
german de
hebrew he
hindi hi
italian it
japanese ja
korean ko
kyrgyz ky
low_German nds
maori mi
mongolian mn
navajo nv
norwegian_Bokmål no
old_English ang
ojibwe oj
persian fa
polish pl
portuguese pt
russian ru
sanskrit sa
spanish es
swahili sw
swedish sv
thai th
turkish tr
ukrainian uk
vietnamese vi
welsh cy
Some languages are better supported than others, depending on the community behind wiktionary. Some languages have most vocab words present, others have many missing.
Written in vanilla javascript/html/css, with python for datascraping.
Here are examples of what it does to your page. Words are replaced with foreign language vocabulary word.