Best AI Detectors in 2026: 10 Tools Compared on 4 Text Samples
We compared 10 AI detectors on four text samples: human prose, AI-generated story, mixed human+AI, and an AI rewrite. Pangram identified mixed text best; Copyleaks was clean on pure text; ZeroGPT and Grammarly both flagged Lewis Carroll as AI.
8 min read
Best AI Detectors in 2026: 10 Tools Compared on 4 Text Samples
Pangram is our first tool to try based on this four-sample comparison: its displayed categories matched all four inputs, and its mixed-text report identified the later AI section. Copyleaks is another candidate for an initial check of fully human or AI-generated text, although it missed the AI portion of our mixed sample.
These are observations from four short English samples, not estimates of overall accuracy or reliability. GPTZero's displayed results remain unverified against the current inputs and are excluded from performance recommendations.
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 + 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; not human-written or a commercial humanizer output. |
We tested 10 product interfaces. Scribbr displayed a QuillBot v7.1.0 panel, so we do not count it as an independent confirmation. Scores below retain each product's own units.
Which AI Detector Should You Try?
| Your priority | First trial and evidence | Important limitation |
|---|---|---|
| Inspect mixed human and AI text | Pangram. M01 received a mixed label, a 37% AI / 63% human split, and a note locating AI content in the later section. | One constructed mixture; long-run accuracy and repeatability were not measured. |
| Screen fully human or AI-generated text | Copyleaks. H01 showed 0% AI; A01 and E01 showed 100% AI, with input word totals. | M01 showed 0% AI despite two known AI paragraphs. |
| Check long documents or many files | No recommendation established. All prepared samples were under 500 words. | Full-length and bulk workflows were not tested. |
Before paying, try text with a source you can verify, confirm that the complete input was processed, and inspect the explanation as well as the label.
Results at a Glance
These are displayed outputs, not accuracy rates. Each product's scale is preserved. "No result" means access was blocked; it is never a zero AI score.
| Product | H01 human | A01 AI | M01 mixed | E01 rewrite |
|---|---|---|---|---|
| GPTZero — input matches unverified | Human 100% — unverified | AI 100% — unverified | Mixed 100%; 13/19 sentences likely AI — unverified | AI 100% — unverified |
| Pangram | Human-written 100% | AI-generated 100% | Mixed; 37% AI / 63% human | AI-generated 100% |
| Copyleaks | 0% AI; 454 human words | 100% AI; 375 AI words | 0% AI; 404 human words | 100% AI; 390 AI words |
| Originality.ai | Likely Original; 100% confidence | Likely AI; 100% confidence | Likely Original; 77% confidence | No result: daily free limit exhausted |
| Undetectable AI | 1% AI/GPT; human-written | 95% AI/GPT; AI-generated | 37% AI/GPT; human-written | 73% AI/GPT; AI-generated |
| ZeroGPT | 99.6% AI GPT | 97.1% AI GPT | 88.1% AI GPT | 15.7% AI GPT; human-written |
| QuillBot | 0% likely AI; Human 100% | 0% likely AI; Human 100% | 0% likely AI; Human 100% | 0% likely AI; Human 100% |
| Scribbr / QuillBot panel | 0% likely AI; Human 100% | 0% likely AI; Human 100% | 0% likely AI; Human 100% | 0% likely AI; Human 100% |
| Grammarly | 100% AI-generated | 100% AI-generated | 100% AI-generated | No result: daily limit reached |
| Sapling.ai | Fake 66.9% — full coverage unconfirmed | Fake 100% — truncated at 2,000 chars | Fake 99.1% — truncated at 2,000 chars | Fake 76.5% — truncated at 2,000 chars |
Product Reviews
GPTZero: Displayed Reports Awaiting Verification
The GPTZero interface displayed human, AI, mixed, and AI labels in sample order. The M01 capture also showed 13 of 19 sentences described as likely AI-generated. However, all four screenshots display "Text changed — Scan to update," so they do not establish that each report had refreshed for the adjacent input. A completed fresh scan of each sample is needed before GPTZero can support a performance recommendation.
Pangram: Mixed-Text Results Explained
Pangram's displayed categories matched all four samples. On M01, it also stated that AI-generated content appeared in the latter part, and its 37% AI / 63% human split was close to the prepared 37.4% AI word share. This makes it the first candidate to try if your priority is inspecting a mixed-text report, based on this single example.
Copyleaks: Clear AI Signals with a Mixed-Text Miss
Copyleaks separated H01 from A01 and E01, with a clear 0% or 100% result in each case, and its word totals made the reported input length visible. M01 exposed the trade-off: all 404 words were treated as human despite the two known AI paragraphs. Copyleaks is a candidate for initial screening based on the pure-text results, but this run does not support relying on it to locate AI-assisted sections.
Originality.ai: Confidence Scores and Free-Scan Limits
Originality.ai's confidence labels aligned with the pure human and AI samples. M01 received 77% confidence in "Likely Original," while the daily limit prevented an E01 report. The tool remains a candidate for a second opinion on pure text, but its confidence percentages are not measured accuracy rates.
Undetectable AI: A Mixed Score Beneath a Human Label
Undetectable AI separated the pure human text from both AI versions. The AI/GPT score decreased from 95% on A01 to 73% on E01, while the headline remained AI-generated. M01 is the reason to read beyond the headline: the page said human-written while showing 37% AI/GPT. That is not the same output as an explicit mixed label.
ZeroGPT: A Human False Positive and a Rewritten-AI Miss
The human control was the clearest concern: ZeroGPT assigned Lewis Carroll's prose 99.6% AI GPT. A01 received a similarly high 97.1%, so a high score alone did not distinguish those two sources. E01 changed the result substantially: the rewritten story received 15.7% AI GPT and a human-written label. ZeroGPT showed both a human false positive and a rewritten-AI miss.
QuillBot: Four Human Labels Across Different Sources
QuillBot v7.1.0 returned the same 0% likely AI and 100% human-written result for all four inputs. The H01 result was appropriate, but A01 and E01 were both produced by AI, and M01 deliberately included AI paragraphs. This shows why a human-only check is insufficient when evaluating a detector.
Scribbr: Results from a QuillBot-Labeled Panel
All four Scribbr-page screenshots contain a detector panel labeled "QuillBot v7.1.0." Its outputs match the four QuillBot-page outputs. We retain this row because it records what a reader encountered on Scribbr, but it is not an independent engine result.
Grammarly: A Strong Human False Positive
Grammarly's first three reports all showed 100% AI-generated. A01 was indeed AI-written, but H01 was historical human prose, and M01 contained both sources. The repeated label makes the human control particularly valuable: this test shows why Grammarly's score should not settle authorship by itself.
Sapling.ai: Scores That Need a Coverage Check
Sapling uses the label "Fake." A01, M01, and E01 explicitly displayed a truncation warning at the free 2,000-character limit. H01 showed 66.9% with full coverage unconfirmed. Sapling's results illustrate why checked length deserves as much attention as the headline score.
What the Comparison Tells Us
Pangram identified AI content in the later part of mixed text
Pangram displayed the expected categories for all four samples, and its M01 report identified the later AI section as well as giving a 37% AI / 63% human split. This is the strongest basis in these captures for a first tool to try on mixed text.
Mixed text reveals more than a pure-AI test
M01 is especially informative because the source boundary is known. Copyleaks and QuillBot reported no AI, Undetectable AI retained a human headline with a 37% signal, and Pangram reported a mixture and identified the later AI section.
False positives and rewriting both matter
ZeroGPT and Grammarly gave strong AI labels to the known human passage. ZeroGPT then labeled the AI rewrite human-written. Together, these observations show why evaluating only one fresh AI output is inadequate: a detector also needs a human control, a mixed sample, and an edited or rewritten comparison.
How to Use a Detector Result Responsibly
Check the input range and refresh state first. Read the label alongside the percentage, inspect any available passage-level evidence, and compare the result with drafts, notes, citations, and revision history. A detector report does not identify the writer or establish their honesty.
Current Access and Pricing
| Product | Free access | Paid plan |
|---|---|---|
| Pangram | 2,000 words/day; no payment method required. | $20/month for 300,000 words/month. |
| Copyleaks | Up to 25,000 characters per free web scan without logging in. | $16.99/month for 100 unified credits, covering up to 25,000 words. |
A listed allowance is not proof of full-document processing. Before choosing a paid plan, check supported input length, file type, language, report detail, and whether the amount is a per-scan limit or a daily or monthly quota.
Frequently Asked Questions
Which AI detector is best in 2026?
Pangram is the first candidate to try based on these four short English samples: its displayed categories matched all four, and it identified the later AI section in the mixed text. This does not establish a universal accuracy winner. Copyleaks is another candidate for pure-text screening, with a mixed-text miss. GPTZero needs fresh completed scans before it can support a performance recommendation.
What is the best free AI detector?
Pangram lists 2,000 free words per day. Copyleaks advertises up to 25,000 characters per free web scan without logging in. Compare them with your document length and verify that the whole input is processed.
Does Scribbr use the QuillBot API?
The tested Scribbr page displayed a QuillBot v7.1.0 panel. The screenshots do not reveal whether it uses an API, embedded component, or another integration. We report the panel attribution and do not count its outputs as a separate independent confirmation.
Can an AI detector prove who wrote a text?
No. These captures show disagreement even on text whose origin is known. Detector output should support review alongside drafts, source material, and a conversation with the writer; it should not determine authorship or academic misconduct by itself.
Can rewriting reliably make AI text pass as human?
This test does not support that claim. E01 remained AI-labeled in several reports but was called human in others. A lower detector score is not proof of better writing.
Final Verdict
Start with Pangram if you want to inspect mixed-text reporting, based on its category labels and identification of M01's later AI section. Consider Copyleaks for an initial pure-text check while keeping its mixed-text miss in mind. The strongest practical lesson is to verify the checked text, the report's refresh state, and the meaning of its score. Those details determine whether a result can support a useful review. Keep drafts and sources as the primary evidence of how a document was written.
