Best AI Detectors in 2026: 13 Tools Compared on 4 Text Samples

We tested 13 AI detector interfaces on the same four short English samples: a known human passage, an unedited AI story, a deliberate human-plus-AI mix, and an AI rewrite. The point was not to crown a single winner but to see which tool handles each job — especially mixed text — and which labels you cannot trust on their own. GPTZero's reports are shown for the record but excluded from recommendations, because every capture still showed a refresh warning and could not be confirmed against the current inputs.

The Four Test Samples

Sample	What we submitted
H01 · Human · 454 words	The opening six paragraphs of Lewis Carroll's Alice's Adventures in Wonderland.
A01 · AI · 375 words	An unedited AI-generated story about Mara finding a brass key in her grandfather's shed.
M01 · Mixed · 404 words	H01's first three paragraphs plus A01's last two. AI supplied 151 words, or 37.4%.
E01 · AI rewrite · 390 words	A rewrite of A01 by the same AI assistant; neither human-written nor a commercial humanizer output.

We recorded each product's own label, units, and any scan limits rather than forcing a common score. "No result" means access was blocked — it is never a 0% AI score.

Which Detector Should You Try First?

Your priority	First trial and evidence	Key limitation
Inspect mixed human + AI text	Pangram. M01 got a mixed label, a 37% AI / 63% human split, and a note locating AI content in the later section.	One constructed mixture; repeatability not measured.
Screen fully human or AI text	Copyleaks. H01 showed 0% AI; A01 and E01 showed 100% AI, with word totals.	M01 showed 0% AI despite two known AI paragraphs.
Review controls after a scan	A detector with passage highlighting and review rows.	Three scans stopped at 250 words; highlight accuracy not verified.
Long documents or bulk files	No recommendation established.	All samples were under 500 words.

All 13 Detectors at a Glance

These are displayed outputs, not accuracy rates. Each product's scale is preserved.

Product	H01 human	A01 AI	M01 mixed	E01 rewrite
Pangram	Human 100%	AI 100%	Mixed; 37% AI / 63% human	AI 100%
Copyleaks	0% AI; 454 human words	100% AI; 375 words	0% AI; 404 human words	100% AI; 390 words
Originality.ai	Likely Original; 100% conf.	Likely AI; 100% conf.	Likely Original; 77% conf.	No result: daily limit
Undetectable AI	1% AI/GPT; human	95% AI/GPT; AI	37% AI/GPT; human label	73% AI/GPT; AI
ZeroGPT	99.6% AI GPT	97.1% AI GPT	88.1% AI GPT	15.7% AI GPT; human
QuillBot	0% likely AI; human	0% likely AI; human	0% likely AI; human	0% likely AI; human
Grammarly	100% AI-generated	100% AI-generated	100% AI-generated	No result: daily limit
Sapling.ai	Fake 66.9%	Fake 100%; truncated	Fake 99.1%; truncated	Fake 76.5%; truncated
T-Checker (third party)	93% human / 2% AI	55% AI	93% human / 2% AI	24% AI
HIX Bypass	Human-written	Human-written	No result: sign-in	No result: sign-in
GPTZero	Human / AI / mixed / AI labels shown, but input matches unverified (refresh warning on every capture).

Scribbr's page displayed a QuillBot v7.1.0 panel and returns the same four human labels, so it is not counted as an independent engine. Solvely's detector showed headline results and review controls, but three scans were cut off at 250 words — before the known AI section in M01 — so its numbers cannot be read as a full-document match.

What the Results Reveal

Mixed text is the real test. Because we knew exactly where the human and AI sections were, M01 exposed who actually locates AI-assisted writing. Copyleaks and QuillBot reported no AI at all; Undetectable AI kept a "human-written" headline while showing a 37% signal; only Pangram called it a mixture and pointed to the later AI section, landing within a point of the prepared 37.4% AI word share.

False positives go both ways. ZeroGPT gave Lewis Carroll's prose a 99.6% AI score, and Grammarly labeled the known-human sample 100% AI. Meanwhile ZeroGPT called the rewritten AI story human. A detector that only gets tested on fresh AI output is missing half the picture — you need a human control, a mixed sample, and a rewritten comparison.

Check the scanned length, not just the headline. Sapling truncated three of four scans at a free 2,000-character limit; Originality.ai and Grammarly hit daily caps; HIX Bypass required sign-in. A missing result or a partial scan is not a verdict.

Method and Limits

Each product received the same four fixed English inputs, and we recorded the visible label, number, limit, and warning rather than averaging unlike scales. There is only one example of each type: M01 is an abrupt paragraph splice, not representative of natural editing; A01 and E01 came from the same AI assistant, not multiple commercial models; and the set does not measure long-run accuracy, multilingual performance, or false-positive rates for non-native writers. Detector results should support review alongside drafts and sources — not determine authorship on their own.

Free Access and Pricing (Checked September 2026)

Product	Free access	Paid plan
Pangram	2,000 words/day, no card	$20/mo for 300,000 words
Copyleaks	Up to 25,000 characters/scan, no login	$16.99/mo for 100 unified credits

A listed allowance is not proof of full-document processing. Before paying, confirm supported input length, file types, languages, and whether the quota is per-scan or daily/monthly.

Frequently Asked Questions

Which AI detector is best in 2026? Based on these four samples, start with Pangram for mixed-text reporting; consider Copyleaks for pure-text screening while keeping its mixed-text miss in mind. No universal winner is established.

What is the best free AI detector? Pangram lists 2,000 free words/day; Copyleaks allows up to 25,000 characters per free web scan. Compare against your document length and confirm the whole input is processed.

Can an AI detector prove who wrote a text? No. On text whose origin we knew, these tools already disagreed. Use a detector as one signal alongside drafts, notes, and the writer's own process.

Can rewriting reliably make AI text pass as human? This test does not support that. The AI rewrite stayed AI-labeled in some reports and human in others, and a lower score is not proof of better writing.

Final Takeaway

Start with Pangram if you want to inspect mixed-text reporting; use Copyleaks for a first pure-text check; and treat any single 0% or 100% score as a prompt to look closer. The strongest practical lesson is to verify the scanned input, the report's refresh state, and what the percentage actually means — then keep drafts and sources as the real evidence of how a document was written.