Thsrs bills itself as “The Shorter Thesaurus.” After you type in a word (using its attractive interface) it will only show you words that have fewer letters than the word you typed.

It’s designed for people who use services like Twitter who have a maximum number of words they can use, but it would be useful to English Language Learners — especially Beginners. A typical thesaurus can be overwhelming to them.

I’ve placed a link on my website under Thesauruses.