QuillBot is an AI writing toolkit centred on paraphrasing — rewriting text in different styles and tones while preserving the original meaning. It is the most widely used paraphrasing tool globally, particularly among students and academics, and has expanded into grammar checking, summarising, citing, and plagiarism detection. A complete writing assistance suite rather than just a rewriter.
QuillBot paraphrases text — it rewrites sentences and paragraphs in different styles while preserving the original meaning. Paste in a sentence, paragraph, or document, select a mode, and QuillBot produces a rewritten version. The core tool is the paraphraser; built around it is a full writing suite: grammar checker, summariser, citation generator, plagiarism checker, and translator.
QuillBot is particularly popular in academic contexts because of its summariser (for research) and citation generator (for sourcing). It is also widely used for professional writing, content creation, and anyone who needs to rephrase text clearly and quickly.
Important for academic users: Using QuillBot to paraphrase source material and pass it off as original writing is academic dishonesty. The ethical use is to rewrite your own ideas for clarity, improve your own draft, or understand how a source might be legitimately paraphrased — not to bypass writing requirements.
QuillBot works best on complete sentences and paragraphs — not isolated phrases. The more context the model has, the more coherent the rewrite. For best results: paste complete, well-punctuated text; choose the mode that matches your goal (Formal for professional writing, Simple for plain language, Academic for scholarly work); review suggestions carefully rather than accepting blindly — QuillBot sometimes changes meaning subtly or introduces new errors.
The word frequency slider (on the paraphraser) controls how much vocabulary changes. Higher = more variation, more creative. Lower = minimal changes, close to original phrasing. For subtle rewrites, keep it low. For thorough paraphrasing, push it higher.
QuillBot uses a sequence-to-sequence transformer model fine-tuned for paraphrase generation. The model is trained on large paraphrase corpora alongside a quality filtering mechanism that penalises outputs that change meaning significantly or introduce grammatical errors. The different modes (Formal, Creative, Simple etc.) are implemented through control tokens or separate fine-tuned variants that bias generation toward the target register while maintaining the core paraphrase objective.
QuillBot was founded in 2017 by Rohan Gupta, Anil Jason, and David Silin at the University of Illinois. It grew primarily through word-of-mouth among students and was acquired by Course Hero in 2021 for approximately $4.25 billion — one of the largest EdTech acquisitions at the time. QuillBot continues to operate independently within Course Hero as a standalone product. Monthly active users exceed 35 million as of 2024 disclosures.
AI paraphrasing detectors (Turnitin's AI detection, Copyleaks, GPTZero) are increasingly able to detect text paraphrased by QuillBot and similar tools, particularly at lower variation settings. This is an ongoing technical race — detector vendors update their models as paraphrasers improve. The Formal and Academic modes tend to produce more detectable output than the Creative mode with high variation. However, AI detection accuracy is still imperfect — false positives and false negatives occur regularly. Academic institutions' policies on AI paraphrasing tools vary; students should check their institution's guidelines.
Source note: Pricing from quillbot.com/pricing. Company background from public records and Course Hero acquisition announcements. All verified April 2026.
Opens your assistant with this page as the source, and a question rather than a summary. It will ask what you are building before it answers.
Nothing is sent from here. The link carries only this page’s title and address.