Кроме того, что не работает на addons.mozilla.org и некоторых других сайтах (скорей всего это проблема гугл переводчика), больше особых претензий нет.
Может переводить выделенный текст, всю страницу и так, как мне нужно. Есть все необходимые настройки.

Need one more feature: input language.

Auto detection doesn't always work well, especially when translating a small passage of text. Japanese is often recognized as Chinese, and you'd never know it, because it display say what language the selected text is detected as. Similarly, Dutch could be detected as German, Spanish as Portuguese, etc.

Input language should perhaps be a priority list of languages you most likely want to translate, and have the translation engine prefer those over whatever is autodetected, if possible.

That's excellent

Good

Very good - simple and fast! Maybe missing option "translate by key"

Bence şuanda en iyisi bu. Çok teşekkür ederim.
Best. Thank you...

Simple, intuitive, quickly accessible and easy way to translate while reading a webpage.

it's great

As described, Simple to use, simple everything

رائع

"Simple Translate" is its name and that's right, it is simple, fast, accurate and very easy to use. I am pleased of using it everyday.

Keep the good work!

Very good minimalistic and open-source alternative to S3.

افضل اضافة ترجمة

This is probably the best translator addon in terms of minimal UI, but is pretty much unusable.

Theres no way to specify the source language.

Many languages, such as Japanese and Chinese have similar letters and words, but have pretty much different meanings. Google translate detects many of my Japanese texts as Chinese. This is where auto-detect language fails and we need to manually change the source language.

Would love an option to listen to the selected text untranslated

I finally found an add-on that is almost identical to the Chrome add-on TransOver (https://chrome.google.com/webstore/detail/transover/aggiiclaiamajehmlfpkjmlbadmkledi?hl=en).

I have a bit of greed about this add-on.
It would be nice to show the definition of a word like TransOver, rather than a Google translation.

Thank you for your efforts.

I've tried it and actually it works great!!
Besides, it needs some improvements, let's say:
+ Language of selected text: Japanese
+ Target language: English

Currently, when I select Japanese text, it translates text to English. It's OK in this case.
But when I select English text (that is same as Target Language), and my setting for second language is FRENCH, then I have to click on the icon button on the toolbar to see the translation to FRENCH, and cannot see directly on Translation Panel.

==> IMPROVEMENT: it is expected it AUTOMATICALLY translates to SECOND LANGUAGE and directly displays on Translation Panel in case Target Language is same as language of selected text.
Many thanks.