Caption - Open-source captioning tool to help find the right subtitles.
Grammarly - Clear, effective, mistake-free writing everywhere you type.
VEED Subtitle - A simple & fast way to add subtitles to your videos online
GrammarChecker.net - Grammar Checker is an online spell check tool. It effectively works on English sentence correction, Punctuation mistakes of 28 other different languages.
Auto Subtitles by Type Studio - A fast & easy way to add auto subtitles to your video online
LanguageTool - Free proofreading tool for OpenOffice, LibreOffice, Firefox, and Chrome.