Indic IME

Indic IME is a lightweight Firefox extension that is mainly intended for Indian users, allowing them to write texts within the browser in their native language, even if the PC's default configuration uses English.
Providing support for 10 Indian writing systems, it can prove useful for writing emails, chatting with friends or posting messages on social websites.
As a drawback, the addon has not received updates in a long time and it is not compatible with the latest versions of Firefox. However, it works like a charm on older versions, provided you have a proper font installed on the system (Open Type Unicode fonts for Indian languages).
Once the extension installed, you can configure it from within the 'Tools' menu. The initial step is to select the desired keyboard layout and you have two available alternatives here, namely WX and Inscript. The first one is a phonetic layout, which means that words are written as they are heard (mostly used by non-native speakers), whereas the latter is mostly used for typing in texts in Brahmic scripts or the Santali language.
There are multiple Indian languages that you can choose from, namely Hindi, Bengali, Gurumukhi, Gujarati, Oriya, Tamil, Telugu, Kannada, Malayalam and Sinhala.
Once these two options are configured, you can try typing in text in any web form or e-mail message creation box within the browser.
Indic IME is a great tool for those who need to input text in an Indian language but want to avoid using inaccurate translation engines. It enables them to write in Indian without having to install a new language pack in Windows.
Unfortunately, it does not provide an updated edition that can be used with recent Firefox versions, which might determine users to look for some other utility that can help them in this matter.