Grammarly is an American cloud-based typing assistant. It reviews spelling, grammar, punctuation, clarity, engagement, and delivery mistakes in English texts, detects plagiarism, and suggests replacements for the identified errors. It also allows users to customize their style, tone, and context-specific language.

Quillbot started out as, and is still primarily, a paraphrasing tool. It uses AI to paraphrase content by rearranging word order and substituting some words for others. However, it has evolved to be much more than that. Primarily of interest to us is the grammar checker, which inspects your document for typos, spelling mistakes, and other grammatical issues.