HumanPen vs Undetectable.ai: who each one is for
One works on complete formatted documents; the other on short text anywhere, backed by a wide toolkit. Which is right depends entirely on what you are handing in.
Competitor details verified 2026-08-01. Their own site is the authority.
The short answer
If you work on complete, formatted documents - papers, reports, decks - HumanPen is built for that. If you work on short scattered text, want a browser extension for casual use, or need a whole suite of adjacent tools, Undetectable.ai fits better.
Side by side
| HumanPen | Undetectable.ai | |
|---|---|---|
| Input | Upload DOCX / PPTX | Paste text, plus a browser extension |
| Output | Editable DOCX / PPTX, layout intact | Plain text |
| Per-request word cap | None (per file, ~200k tokens) | 3,000 words on the $36/mo top tier |
| Detection report import | Turnitin / iThenticate, flagged passages only | None |
| Billing | Metered credits, never expire, failures not charged | Monthly subscription |
| Free tier | 100 credits (1,000 words) | 250 words, 3-day trial |
| Adjacent tools | Citation styles, condense, translate | 30+ tools |
| Rewrite languages | English only | Multiple |
When to pick Undetectable.ai
- You are working on scattered web text - blog paragraphs, social copy, email replies. Their extension works on a selection; we ask you to upload a file, which is pure overhead here.
- You want a full toolkit. They run 30+ tools under one account. We have four, all built around academic documents.
- You need a language other than English. Our rewrite engine is English-only today, and there is no way around it.
- You run high monthly volume and formatting does not matter. At content-team scale a subscription is cheaper per word.
- You want a large free trial before paying. We give 100 credits and that is it.
Where we stop
HumanPen is shaped around one thing: a document you have to hand in. Whole DOCX or PPTX in and out, formatting and citations untouched, Turnitin report import to rewrite only flagged passages, billing on words actually rewritten, credits that never expire.
The cost is that it is slower and heavier than a text box, wrong for a stray paragraph, and has no extension. That is a trade-off we chose, not an oversight.
FAQ
Can I use both?
Yes, and plenty of people do - an extension for scattered text, and us for the document that gets submitted.
Which one is more effective?
There is no honest general answer. Detection systems keep updating and text types differ, and we have run no head-to-head test, so we will not hand you a number we made up. Try each on your own writing - our 100 free credits cover a real section.
How do the prices compare?
The billing logic differs, so unit prices are not comparable. Subscriptions suit steady high volume; metered credits that never expire suit a few papers a semester. Work it out against your own usage.
Do you have a browser extension?
No. We process whole files, and an extension does not help much with that.
The only comparison that settles it is your own document
New accounts get 100 credits - enough to run a full section of your own writing through and judge the result yourself.
Try it on your document