Free · nothing uploaded
Check your writing for an AI provenance mark
Up to 1,500 words at a time. The engine downloads to your browser and your text is measured there, so there is nothing for us to store, log or hand to anyone.
0 / 1,500 words
Paste, drop a file, or upload .txt, .md, .rtf or .csv. Everything is read and processed on your device.
After the check
Want the evidence reduced as well as measured?
The main NeverPrompted flow rewrites the passages that carry detectable AI-style evidence and then runs this exact check on the result, so you see the text and the measurement together. Same engine, same on-device guarantee, one step.
Answers, in full
Before you read too much into a result
- Is a detected mark proof I used AI?
- No. A detected mark is not proof of authorship. Marks can appear in text that was quoted, translated, edited, or written with assistance, and a statistical test reports a probability rather than a fact about a person. NeverPrompted reports the strength of the signal and the passages carrying it, and states this limit on every result and every exported report.
- Can this tool guarantee my writing won't be flagged?
- No, and any tool that claims a 100% or guaranteed result is overselling a probabilistic process. NeverPrompted can reduce detectable AI-style evidence: both statistical watermark signal, where structurally possible, and human-perceptible AI tells like em dashes and stock phrasing. It cannot guarantee defeating a model vendor's undisclosed watermark, because nobody outside that vendor holds the key it was applied with, and no honest tool can promise otherwise. The rewrite runs entirely on your device, on every tier, and shows you the before/after evidence so you can judge the result yourself rather than take a guarantee on faith.
- Does NeverPrompted detect ChatGPT's or Claude's watermark specifically?
- Not unless this deployment holds that vendor's detection key, and no vendor currently publishes one; the result lists exactly which keys were tested, under "keysTested", so you can see that for yourself rather than take a claim on faith. NeverPrompted also reports a separate, key-free "AI-style likelihood" score: a heuristic that flags surface habits common in Claude, ChatGPT and other current model output (dash-clause connectors, stock phrasing, elevated vocabulary, uniform sentence length), deliberately biased to catch more real AI writing rather than to minimise false positives. It is not a statistical test and it is not a substitute for a real watermark result; see /guide/claude-ai-watermark for what a provenance mark actually is and why the key is the whole story.
- What's the difference between the Standard and Pro rewrite engines?
- Standard is deterministic substitution against the core AI-tell library: instant, no download, and included on every plan. Pro is a real language model that runs in your browser, generating more candidate rewrites per passage and using the extended AI-tell library; it comes with a Pro subscription rather than being metered on the free plan. What the free plan meters is how much rewriting you do: 20,000 tokens every 7 days, where a token is one word as this product counts them. Checking is never metered on either plan. Neither engine ever sends your text anywhere.
- Does my document ever leave my device?
- Not on the free check, and never on the rewrite feature, on any tier or surface. Checking runs in your browser: the detection engine is downloaded to your device and the text is measured there; you can confirm it by opening your browser network tab and watching while the check runs. The API, the MCP server and the PDF evidence report necessarily run on our servers for CHECKING, because a programmatic caller has no browser, and those paths are documented separately and are opt-in. Rewriting is different and stricter: it runs entirely on-device or in-process everywhere, in the browser, the API package, and the MCP server alike, with no hosted mode at all, on any tier.
- Which languages are supported at launch?
- English, Spanish, French, German and Portuguese. Each has its own reference baseline measured from real contemporary prose in that language; a language without a measured baseline is reported as unsupported rather than analysed against a substitute, because comparing Portuguese text to a Spanish reference produces deviations that look like findings and are artefacts.
- An absent mark: does that prove I wrote it myself?
- No, and this matters as much as the first answer. Marks survive editing poorly, are not applied by every system, and cannot be detected at all without the key used to apply them. No model vendor publishes its detection key. NeverPrompted tests the keys it holds and names them, so "no mark detected" always means "under these keys" and never "this document is clean".
- What can I actually hand to someone who has accused me?
- The Pro evidence report: a dated PDF carrying the signal strength with its confidence band, the per-passage breakdown after false-discovery-rate correction, the full stated limits, the list of keys tested, and a SHA-256 hash of the exact document analysed. The hash is what ties the report to one specific file, so the report cannot be waved at a different draft.