The upload button was not the document test

Two AI humanizer pages showed me an upload control this week. I still left the editable-return column blank.

On undetectable.com, the logged-out input area showed Paste Text, Upload Doc, and a 0 / 2,000 words counter. Grammarly's current AI Humanizer page had an Upload file control too.

Both observations show that the public pages offer a file-upload entry point. They do not prove that a selected file is accepted or what comes back.

That sounds fussy until the input is a DOCX with footnotes, fields, citations, and tables, or a PPTX where one extra line can overflow a text box. Upload is an intake event. A document round trip includes the output format, editability, document structure, and the parts that were supposed to stay untouched.

The checked undetectable.com page did not state that an uploaded document returns in the same editable format. The checked Grammarly page did not state that either. That is not a claim that either product lacks the feature. It means the two upload controls cannot carry that conclusion on their own.

I did not submit a document to either product during this research. So I do not have a format-retention result to report. What I have instead is the acceptance test I would run before trusting any humanizer with the real file.

Make the test disposable and small. It should still contain the structures that make the real document expensive to repair:

1. Save a clean copy and record the exact input extension.
2. Add a heading, a footnote, one in-text citation, a numbered list, and a small table to a DOCX. For a PPTX, add a text box close to its lower boundary and one slide with notes.
3. Mark one paragraph as the intended rewrite scope. Put a distinctive sentinel sentence in a paragraph that should stay outside that scope.
4. Run the public workflow on the exact tier you plan to use. Record the date, tier, displayed counting unit, and every file the product lets you download.
5. Open the result in Word or PowerPoint, not only in a browser preview. Record the extension, whether normal editing still works, and whether fields or linked elements remain live.
6. Compare the clean input with the result. Check the selected paragraph, the sentinel paragraph, citation text, footnote numbering, table cells, list numbering, slide overflow, and notes.
7. Keep both files and the checklist. A screenshot of the upload button is not evidence for any item after step four.

The protocol is deliberately boring. Every row has a result another person can inspect. DOCX in and DOCX out are observable. "Looks fine" is not. A field that still updates is observable. A familiar page layout in a screenshot is not.

It also keeps vendor claims in the right column. If a page promises same-format editable return, write that down as a public claim before the run. Then test it. If a page only shows an upload control, write down exactly that and leave the return field unresolved until the workflow produces evidence.

The same discipline applies to scope. A product may accept a full file yet rewrite more of it than you wanted. The sentinel paragraph makes that visible. If the selected paragraph changes and the sentinel does not, you learned something useful about this run. If both change, you caught the mismatch on a disposable file.

Our product is HumanPen. Its public pages list DOCX, PPTX, and TXT as accepted inputs and promise editable Word and PowerPoint returns. They also describe passage selection that leaves text outside the confirmed boundary unchanged. Those are vendor statements. HumanPen should go through the same acceptance protocol rather than receiving a free pass because we wrote the protocol. Eligible results can continue lowering AI for free.

None of this predicts what Turnitin will show afterward. The test answers a different question: can the document survive the workflow you are about to depend on?

An upload button is evidence that the page offers a file-upload entry point. Stop there, and successful intake remains unresolved. Follow the file all the way back into its native editor, and the marketing label turns into a testable contract.

Originally published at HumanPen: https://humanpen.net/blog/ai-humanizer-comparison-2026?utm_source=devto&utm_medium=article&utm_campaign=D96