Best AI Detector software

Accuracy is independently verified, not just claimed: researchers at the University of Chicago and University of Maryland found Pangram posted the lowest false positive rates against competing detectors, with a documented 1-in-10,000 false positive rate measured across tens of millions of human-written documents.

Segment-level analysis goes beyond a single score by highlighting exactly which parts of a document are AI-generated versus AI-assisted, so mixed human-and-machine writing can be explained with concrete evidence.

Exact plan prices aren't shown on the homepage, and Educational Institution and Enterprise tiers require contacting sales for a quote, so budgeting takes extra legwork.

Plagiarism detection is locked behind paid plans — free users get AI and image detection only, and free image checking is capped at just 3 scans per day.

Genuinely free to use with no account or sign-up required, so you can run a check the moment you need one

Accepts both pasted text and URLs, letting you check drafts and already-published pages with the same tool

It is a simple verification tool, not a forensic one — you get a score, not sentence-level breakdowns, source attribution, or detailed reporting

No batch processing or API access, so teams screening high volumes of content will need a more robust platform

Provides per-word probability estimates rather than just a single document score, letting reviewers see exactly which tokens look machine-generated.

Highlights suspect passages inline, making it much faster to locate and discuss AI-written sections in long documents.

Detection is probabilistic and can produce false positives—particularly on writing by non-native English speakers or formulaic human prose—so flagged text still requires human review.

Accuracy is calibrated against current mainstream models like ChatGPT and Gemini; newer, fine-tuned, or heavily paraphrased AI output may evade detection.

Runs AI detection, plagiarism, fact checking, and content quality checks in a single scan instead of making you juggle separate tools

Actively tests paraphrasing tools like Quillbot and Grammarly, so AI text reworded to look human still gets flagged

False positives happen: the vendor's own FAQ discusses what causes them and cautions that a score shouldn't be used on its own

The free tier caps you at 3 scans a day and 2,000 words, which runs out quickly on real agency or publishing workloads

Combines AI text detection, plagiarism checking, and AI image detection in one platform instead of requiring three separate services

Free account provides immediate access, so you can validate detection quality on samples with known origins before paying

Detection is probabilistic, so false positives on human writing and misses on heavily edited AI text remain possible and demand human review

Accuracy claims are vendor-stated; institutions should verify performance on their own known-origin samples before relying on scores for high-stakes decisions

Originality checking is built into the same platform institutions use to create, deliver, and grade assessments, so staff don't have to export work to a separate detector.

Integrity tools are layered rather than isolated: Inspera Originality pairs with the Integrity Browser for locked-down exam environments and Proctoring with adjustable monitoring levels.

The original Crossplag AI detector page returns a 404, so the standalone tool can no longer be evaluated or purchased at its old address, and its published claims — including training on over 1.5 billion parameters and English-only support — cannot be verified against a live product.

No pricing is published anywhere: buyers must book a demo and negotiate with Inspera's sales team, and trial, refund, and cancellation terms are not stated publicly.

Detects output from a broad range of LLMs, explicitly including GPT-5, Gemini, and Claude, rather than being tuned to a single model family.

Reports separate human-written sections from AI-generated sections within the same mixed document, giving reviewers specific passages instead of one blanket score.

Like every AI detector, results are probabilistic; false positives and false negatives can occur, so a flagged score should never be the sole basis for a consequential decision.

Detection accuracy can lag behind brand-new or heavily paraphrased LLM output as models evolve and users learn to mask machine patterns.

Pinpoints which sentences look machine-generated rather than returning only a document-level score, so feedback can cite specific passages

Uses multiple signals—perplexity, burstiness, and tone repetition—instead of relying on a single heuristic

AI detection is probabilistic; a flag is a signal to investigate, not proof of misconduct, and human writing can occasionally score as AI-generated

Top-tier pricing reaches $504/month, which is steep for individual users, and heavy scanning may trigger usage-based charges