Criterion CheckWise AI QuillBot
CategoryAI Detection & Plagiarism CheckingAI Writing & Content Creation
In one sentenceAn independent document-analysis service that runs an AI-writing check and a similarity (plagiarism) check on the same upload.A suite of writing tools for paraphrasing, summarising, grammar checking and AI detection, popular with students.
Problem it solvesGives students, researchers, writers and businesses a quick, pay-per-check way to see whether a document shows AI-writing signals or closely matches existing sources, without a subscription.Rewording, condensing or checking text by hand is slow, especially for students and non-native writers.
Free planNoYes
Developer APINoNo
Open sourceNoNo
PlatformsWebWeb, Browser extension, Microsoft Word, Google Docs
Pricing (summary)Each account gets 1 free check (AI and similarity reports) until 1 January 2027, with no credit card. After that you buy one-time token packs: Starter $3 for 1 check, Plus $25 for 10 checks, Business $200 for 100 checks. Tokens are valid for 30 days; there is no subscription.
Checked 2026-10-19
Free tier with word limits. Premium is shown at $8.33/month billed annually ($99.95/year); QuillBot's FAQ lists $19.95 for monthly billing. Team plans start at $7.50 per seat per month for 2-10 seats. Prices can vary by region.
Checked 2026-10-19
Strengths
  • AI analysis and similarity check combined in one check
  • Simple per-check pricing with no subscription
  • Clear data-handling statements: own server, no training on documents, 90-day purge
  • Says plainly that AI detection is probabilistic
  • Generous free tier
  • Low-cost annual plan
  • Simple interface
Limitations
  • AI detection can produce false positives and false negatives — the site says a score is an indicator, never proof
  • The size and scope of the similarity index are not described
  • No API or LMS integrations are listed
  • Purchased tokens are valid for 30 days
  • Supported languages are not stated
  • Free paraphraser limited to 125 words and two modes
  • Prices vary by region
  • AI detection results are probabilistic