What AI detectors actually measure
AI detectors do not have a magic 'is this AI' switch. They estimate two statistical properties: perplexity (how surprising each next word is, given the previous ones — AI text tends to pick the most-likely next word, so its perplexity is lower than human text) and burstiness (the variation in sentence length and complexity — humans write in bursts, AI tends to produce uniform sentences). A detector combines these signals into a probability score. Like any statistical classifier, it is correct most of the time but can be wrong in both directions: confident, well-edited human writing can score as 'AI', and lightly-rewritten AI text can score as 'human'.
Why detectors are not proof
Multiple studies (Stanford, MIT, OpenAI's own deprecated classifier) have shown false-positive rates of 5–15% on human-written text, with higher false-positive rates on non-native English writing. Universities and publishers that use AI detectors as the sole basis for plagiarism allegations have lost legal cases. Treat the detector output as a screening tool: a 'likely AI' score is a prompt to investigate, not a verdict.
How to use the result responsibly
If you are a writer running your own text through a detector, treat anything above 50% AI-likelihood as a signal that your prose is too regular and predictable — vary sentence length, add idiosyncratic word choices, and the score will drop. If you are a teacher or editor, never use a single detector output as evidence of misconduct; require process artefacts (drafts, version history, in-person discussion) instead.
What AI Detector is built for
AI Detector solves a single, well-scoped task on files without the usual web-tool friction: no signup wall, no email gate, no upsell prompts, no watermark, no daily quota and no file-size limit beyond what your device's RAM allows. The interface is deliberately minimal — pick your input, set any options, click the action button, download the result. Everything from upload to download usually takes less than ten seconds. Because the tool focuses on a single job rather than trying to be a do-everything suite, the defaults are tuned for that job and rarely need adjustment.
How AI Detector runs in your browser
Most operations happen locally using modern browser APIs (Canvas, File, Web Workers, WebAssembly) so your data never has to leave your device. That matters for personal documents (IDs, statements, certificates), confidential business files (contracts, invoices), and anything else you'd rather not hand to a third-party server. Where a step genuinely needs server help (only true for AI-powered tools), we route through a trusted AI gateway and discard your input immediately after the response is returned. There is no analytics pixel attached to the file itself, no fingerprinting of the document, and no copy persisted in cloud storage.
Where AI Detector fits in a workflow
Real work is a chain of small steps: download a file → fix one thing → re-upload. AI Detector owns one link in that chain and tries to do it well — sharp output, predictable behaviour, no surprises. Pair it with the other free tools on this site (compressors, converters, resizers, PDF utilities, QR generators, AI writing helpers) to handle the entire chain without leaving the browser. The fewer tabs your workflow needs, the faster you finish, and the lower the risk of a sensitive file leaking through a third-party converter.
Free, private and unlimited use of AI Detector
There is no premium tier. The tool is free because hosting static JavaScript costs us almost nothing, and we'd rather earn trust than rent attention with paywalls. Use it once a year or a hundred times today — the experience is the same. If a tool ever does require a server call (AI features specifically), that call is metered at our cost, not yours, and you will never be asked for a credit card to access the basic functionality. We do not insert affiliate links into outputs, we do not stamp watermarks on downloads to push upgrades, and we do not impose 'pro' formats behind a paywall.
Browser support and device compatibility
AI Detector runs on every modern desktop browser (Chrome, Edge, Firefox, Safari, Brave, Arc) released after 2021, and on every modern mobile browser including iOS Safari and Android Chrome. There is nothing to install, no extension to approve and no permission to grant beyond standard file access when you pick an upload. On slower phones the heaviest tasks (image compression of multi-megabyte photos, PDF merges of long documents) may take a few extra seconds while the device's JavaScript engine catches up, but the work still completes locally. If you hit a memory error on a very low-end device, refresh the tab and try a smaller batch — every tool here is stateless, so a refresh is harmless.
Quality, security and trust
Because nothing is uploaded, there is no question of who can see your file in transit, where the server lives, or how long the provider retains a copy. The browser is the sandbox. The code that runs is the same code that ships to every visitor — auditable in the page source. We follow standard web security practice: HTTPS-only delivery, Subresource Integrity on third-party scripts, and a strict Content Security Policy that prevents arbitrary third-party code from running on the page. For organisations that need to demonstrate due diligence on a 'no data leaves the device' claim, the network tab in any browser's developer tools confirms that processing a file generates zero outbound requests with file contents attached.
Tips for getting the best result with AI Detector
Start from the highest-quality source you reasonably can — AI Detector preserves quality but cannot invent detail that isn't in the input. For images, prefer the original camera file over a screenshot of a screenshot. For PDFs, prefer the digitally generated original over a phone photograph of a printout. If a step in your workflow is going to compress or downscale, do it last, so each earlier step still has full information to work with. And when a portal you are uploading to enforces an awkward limit (a strict 50 KB cap, an obscure aspect ratio, a single-page-only restriction), check the tool list — there is almost certainly a dedicated tool here that handles that exact constraint without you needing to learn the maths.