An AI detector for long documents, up to whole books

This AI detector for long documents takes a novel, a thesis or a full manuscript in a single check: paste the text or open a .docx file below. It finds the chapters, shows where the higher-scoring passages sit and, for fiction, adds a narrative fingerprint. It is free, needs no account, and the manuscript never leaves your computer.

Why check a long document here

• Free, with no sign-up. No account, no email and no credit card. No credits, no daily cap, no per-word price, no paywall and no premium tier.
• No word or character limit. Paste a whole thesis or novel and check it in one go. No splitting into chunks.
• Nothing is uploaded. The check runs in your browser, so an unpublished manuscript or an embargoed thesis never leaves your device.
• Your text is never stored, shared, sold or used to train anything. We never receive it.
• Every word is scanned, never a sample, from the first chapter to the last.
• A report that explains itself: an AI-likeness score, sentence-by-sentence highlights, a chapter-by-chapter view, style notes with one-click plainer wording, a hidden-character and look-alike-letter cleaner, and a narrative fingerprint for fiction.
• Opens .txt and .docx files right in the browser.
• No ads where you paste text.

Whole books in one check

There is no limit on words, characters or chapters. A 208,000-word novel has been analysed in one go, and every word is scored, never a sample. Partial results appear while the scan runs, and a cancel button lets you stop at any point. Above 30,000 words the text is shown in pages of 5,000 words with a chapter jump menu, so even a long book stays easy to move around in.

How the AI detector for long documents shows chapters

Chapters are found from their headings, so a manuscript laid out with “Chapter 1”, “Chapter 2” and so on gets a result for each one. This is where checking a long document properly pays off. One overall verdict on a 90,000-word book says very little; a chapter that scores well above its neighbours tells an author or editor exactly where to start reading, and that chapter's drafts and history are the natural next place to look.

A narrative fingerprint for fiction

For fiction, the report adds a narrative fingerprint: simple counts of storytelling features in your manuscript. They include how much of the text is dialogue, how often smell turns up in descriptions, how often the narrator spells out what a scene means, direct address to the reader and markers of jumps in time. Each count sits beside the human and AI base rates published in StoryScope, a study of AI fiction by Russell and colleagues (COLM 2026). That research found that AI and human stories differ in their narrative choices as well as their wording. AI stories, for instance, tended to explain their themes outright.

The fingerprint describes rather than judges. Our counts are inspired by the paper and never feed into the verdict, which makes them useful editorial feedback even when nobody suspects AI at all. There is more on this in how AI fiction differs.

Theses, reports and other non-fiction

A thesis, a long report or a book-length article goes in the same way as a novel: one check, with chapters found from their headings. For academic work, the style notes are a useful extra. They mark stock phrases such as “plays a crucial role” and words such as “underscore” and “paramount”, and offer a plainer wording you can apply with one click. A thesis is also exactly the kind of document you may not want on someone else's server before it's examined or published, and here it never leaves your device.

How to check a manuscript or thesis

1. Save the document as .docx or .txt, or select all of it and copy.
2. Put each chapter heading on its own line, for example “Chapter 12”, so chapters can be found.
3. Open the file or paste the text in the box above, and press Check for AI.
4. Read the overall outcome, then use the chapter menu to jump to any chapter.
5. For fiction, open the narrative fingerprint and compare each feature with the published base rates.
6. Keep the result with your drafts if you need a record: download it as JSON, save it as a PDF or copy a short summary.

Our methodology page explains how the detector is tested.

Sources

1. StoryScope: Investigating idiosyncrasies in AI fiction (arXiv 2604.03136), checked October 2026