Noplag Engine vs Originality.ai

Noplag Engine is an open-source plagiarism detection tool that checks text for verbatim and near-verbatim matches against a corpus you control. It uses winnowing fingerprints to find candidate sources, then aligns matching character ranges. Reports show similarity by source, passage offsets, and coverage accounting. It accepts.txt,.md,.pdf, and.docx files, with folder ingestion and HTTP uploads, and exposes a /v1 API for checks, reports, uploads, progress events, and corpus management. The API ships without authentication. The open-source engine searches a local corpus; the hosted product also searches the live web. It does not detect paraphrase, semantic similarity, or AI-written text. The engine can run on your own hardware with Docker Compose under the Apache 2.0 license. The repository lists Python 3.12 or newer for development and PostgreSQL in its Docker Compose setup. The free hosted plan costs nothing and allows 3 checks per month, while self-hosting permits unlimited local checks. Pro costs $9.99 a month and Premium costs $19.99 a month; Enterprise pricing is custom.

Originality.ai provides tools for checking AI-generated text, plagiarism, facts, readability, grammar, spelling and content quality. Its free Basic plan costs $0.00 per free and provides three AI scans per day, with up to 2,000 words per scan. The AI detector offers configurable allowances of 0%, 5%, 15%, 25% or 40%. A website scanner can crawl a site, identify pages likely to contain AI-generated content and run scheduled scans. The browser extension scans Google Docs, web pages or selected text, and includes writing replay, typing behavior insights and shareable reports. A REST-based API submits text for AI and plagiarism scans and returns detailed results; the maker says AI detection supports 30 languages. API AI scans require at least 50 words, and the help page says accuracy decreases below 100 words. Originality.ai describes detection results as probabilistic estimates that may produce false positives or false negatives, not conclusive proof. Pro costs $12.95 per month billed yearly, with a monthly option at $14.95 per month. The service is available through web, API and extension.