Copyleaks AI Detector vs Plagius

Copyleaks AI Detector identifies AI-written text, including writing that mixes AI and human passages. It supports more than 30 languages and names GPT-5, GPT-4, ChatGPT, Claude, Gemini, DeepSeek, Llama, Bloom, Rytr, and Jasper among the sources it detects. AI Logic explains flagged results, displays AI phrase frequency, and can identify text appearing in published content elsewhere. The web detector scans up to 25,000 characters without login; the website platform requires at least 255 characters and accepts up to 2,000 pages. A Chrome and Edge extension accepts 350 to 25,000 characters, and a Google Docs add-on and education LMS integrations connect it to other workflows. Personal costs $13.99 a year with annual billing or $16.99 a month; Pro costs $74.99 a year with annual billing or $99.99 a month. A free plan and free trial are listed. Copyleaks says data is encrypted at rest with AES-256, reports SOC 2 and SOC 3 certifications, and supports GDPR compliance.

Plagius Desktop analyzes academic papers and other documents for possible plagiarism, checking the internet or local files. It supports Word, PDF, OpenOffice, PPT, HTML, RTF, and plain-text formats. Reports can identify suspicious phrases and sources, display URLs with similarity percentages, estimate suspected-plagiarism percentages, and show analysis-quality indicators; results can be opened in a browser or exported as HTML. Its V5 AI detector analyzes paragraphs in context and returns an AI-generation probability and confidence level. The site says it recognizes signals from more than 15 models, including Gemini 3.7, GPT 5.6, and Claude 5. Professional desktop plans add local and network-share searches, batch analysis, direct URL analysis, and file comparisons. The maker says desktop analysis is performed locally, but external searches may send text fragments, usually 7 to 13 words, to search engines. AI detection may send isolated paragraphs to Plagius servers, where excerpts are deleted within up to 48 hours. A free demo runs analysis but reveals only some results. Plagius One is browser-based and initially limited to invited users. Plagius Basic costs $6.90, paid once; its license lasts 30 days and is for one Windows computer. The maker cautions that automated results need manual review and cannot alone confirm plagiarism.