QuillBot

QuillBot develops AI-powered writing software, including tools for paraphrasing, grammar checking, summarizing, plagiarism detection, and citation generation. The company was founded in 2017 by Rohan Gupta, Anil Jason, and David Silin, then computer science students at the University of Illinois Urbana-Champaign, after an early version of their paraphrasing tool gained traction on Reddit. QuillBot is headquartered in Chicago, Illinois, with additional offices in Bengaluru, Berlin, and the Netherlands.

The company's flagship Paraphraser is complemented by more than 50 tools spanning grammar correction, summarization, AI detection and humanizing, translation, PDF editing, and citation generation, distributed via web, browser extensions, and mobile and desktop apps. QuillBot reports over 35 million monthly active writers and about 5.3 billion paraphraser inputs annually, with a user base weighted toward students, academics, and professional writers. Co-founder Rohan Gupta leads the business as CEO.

QuillBot raised a $4.25 million seed round led by Sierra Ventures and GSV Ventures in 2020 before being acquired by Course Hero in August 2021. Course Hero reorganized as Learneo, Inc. in 2022, and QuillBot now operates as one of Learneo's principal businesses alongside Course Hero, Scribbr, Symbolab, LitCharts, and CliffsNotes. The QuillBot unit employs roughly 225 people across its Chicago headquarters and international offices.