HumanPen vs StealthWriter: a detector on the homepage, or a file workflow
StealthWriter rewrites pasted text and lets anyone run its AI detector without an account. HumanPen works on your .docx or .pptx and reads the Turnitin or iThenticate report you bring.
Competitor details verified 2026-09-11. Their own site is the authority.
The short answer
StealthWriter is a web rewriter for pasted text, with a free AI detector anyone can use without an account. Its plans count runs per day, so it fits short pieces you rewrite often. HumanPen is for a finished English .docx or .pptx that you want rewritten inside the file, following a Turnitin or iThenticate report if you have one.
Side by side
| HumanPen | StealthWriter | |
|---|---|---|
| Input | Upload the document itself | Paste text (rewriting needs an account; the logged-out page only has the detector box) |
| Output | The same file back, still editable | Text, with up to 3 alternative rewrites per sentence; no file return described |
| Per-request word cap | None | Free 1,000 words; 5,000 words on every paid plan |
| Detection report import | Turnitin / iThenticate, flagged passages only | Not stated |
| Word-count control | Set a target word range; output converges on it, slight drift possible | Not stated (rewrite levels 1–10 only) |
| Billing | Metered credits, never expire | Monthly or annual subscription, counted in humanizations per day (10 to 2,000), reset at midnight UTC |
| Adjacent tools | Citation fix, condense, translate | Built-in AI detector (V1 / V2, Deep Scan) |
| Agent / API integration | Skill, MCP, and REST API — callable from AI agents | None (its FAQ: "there is no public API") |
| Rewrite languages | English only | Multiple (Spanish, French, German, Italian, Portuguese, Dutch and more) |
When to pick StealthWriter
- You want a detector. StealthWriter's is on its homepage and runs without an account, in two versions, with a sentence-level Deep Scan on every plan including Free. HumanPen has none: you bring a Turnitin or iThenticate report, or pick the passages yourself.
- You want to try before you sign up. The detector needs no account, and the free plan needs no card: 1,000 words per input, 10 humanizations a day.
- You rewrite lots of short pieces every day. Only the first Humanize on a text counts toward the daily quota; Rehumanize and Humanize More don't.
- You like choosing sentence by sentence. Click any sentence and it offers up to 3 alternative rewrites.
- You need a language other than English. It lists Spanish, French, German, Italian, Portuguese, Dutch and more; HumanPen only works in English.
Paste-sized pieces, or the whole file
Its public pages describe a paste-in, text-out flow: paste text, choose a rewrite level from 1 to 10, click Humanize, and get text back. The FAQ recommends pasting plain text and offers to strip markdown first.
Every paid plan has the same 5,000-word cap per input, from Starter at $20 a month to Scale at $400; higher plans add more runs a day. So a 12,000-word chapter goes in as at least three pastes, and you fit the results back between your headings, tables and citations.
HumanPen has no per-request cap. You upload the .docx or .pptx, rewrite the whole document, passages you pick, or the ones a Turnitin or iThenticate report flagged, and get back an editable file of the same type.
If a recheck still flags something, bring the new report. Eligible passages can be re-run at no charge.
FAQ
StealthWriter has a free detector. Why do you not have one?
If you want a score right next to the rewrite, that's a fair reason to choose StealthWriter. Its score comes from its own model, though. If your school uses Turnitin, the Turnitin report is the one that counts, and that's the report HumanPen reads.
Is the 5,000-word limit the same on every paid plan?
Yes, as of 11 September 2026: 5,000 words per input on Starter, Plus, Pro, Business, Scale and Enterprise, and 1,000 on Free. The plans differ in how many humanizations you get a day. Plans change, so check its pricing page.
Which one is more effective at lowering AI scores?
We haven't tested the two side by side, so we don't have a number to give you. The most reliable comparison is to run your own file through each one.
Can I call StealthWriter from an agent or a script?
Not at the moment. Its FAQ says it's a web-only tool with no public API, and that one may come later. HumanPen has a REST API, an MCP server and a Skill, all on the same credit balance.
Compare the results on your own document
Use your signup credits to try a small selection of paragraphs. Upload a copy, then compare the returned file with the original.
Try it on your document