ScanForAI vs GPTZero: the score, or the reasons.
GPTZero is the best-known name in AI detection, especially in education. ScanForAI is built around one difference: every score comes with the marked lines and plain-English reasons behind it — free while in beta.
The short version.
| ScanForAI | GPTZero | |
|---|---|---|
| Price | Free while in beta — scanner, accounts, history, API | Free tier with tight limits; paid plans for real use |
| What you get back | Score plus the evidence: AI-leaning lines marked in your text, patterns named in plain English | Headline probability with summary highlights |
| Framing | A signal, not a verdict — failure modes documented on the accuracy page | "Probability AI" percentage |
| If a student disputes | Per-line breakdown + PDF report — evidence both sides can discuss | Score-first; deeper docs on paid tiers |
| Per-scan size | 20,000 chars anonymous · 50,000 free account | Smaller on the free tier |
| Extras | Cleanup free · batch scan · URL scan · API | Writing reports, LMS integrations (paid) |
Competitor details paraphrased from public pages, last reviewed July 2026, and may change — check gptzero.me for current terms. GPTZero is a trademark of its owner; ScanForAI is not affiliated with or endorsed by it. We publish no accuracy percentages for either tool — nobody's are independently settled.
When GPTZero is the right call — and when we are.
GPTZero earned its name recognition: it's the default in many schools, and if your institution already standardizes on it, use it. Where ScanForAI is built differently is what happens after the score. A percentage alone can't be discussed — a marked-up text can. We show which lines read machine-written and why, so a flag becomes a conversation instead of a verdict.
Run us as the second opinion
Two detectors agreeing means more than one. Paste the same text here before acting on any single tool's flag — it's free.
Flagged by GPTZero?
Scan your draft here, export the per-line PDF report, and bring evidence to the conversation. See our student guide.
Teachers: evidence beats accusation
Our result shows the reasons in plain English — the difference between "the tool says 87%" and "these six lines read machine-written, here's why."
Where we say no
We don't do "probability a human wrote this" theatre, and we tell you when text is too short to judge instead of guessing.
Common questions.
Is ScanForAI a free GPTZero alternative?
Yes — the scanner, accounts, history, batch and API are free while in beta. The bigger difference is the output: we mark the AI-leaning lines in your text and name the patterns in plain English, rather than returning a probability alone.
Which is more accurate, ScanForAI or GPTZero?
Nobody can honestly answer that — independent studies show every detector, including the biggest names, misses rewritten AI and sometimes flags human writing (formal and non-native writing most of all). That's why we show our evidence per line and publish our failure modes instead of an accuracy number.
I was flagged by GPTZero — what now?
Get a second opinion here (free), export the per-line PDF report, gather your draft history, and ask for a conversation rather than accepting a verdict. No single detector score is proof, and most institutions know it.
Can I use both?
That's often the smartest setup: run both and only act when they agree. Detectors with different methods failing the same way is much stronger evidence than one tool's percentage.
Is GPTZero free?
GPTZero has a free tier with per-scan and monthly limits; serious use sits on its paid plans. ScanForAI is fully free while in beta — scanner, accounts, batch, API — which makes it a zero-cost second opinion even if your school pays for GPTZero.
Why did GPTZero flag my essay as AI?
Formal structure, even sentence lengths, careful grammar and formal vocabulary — the habits of disciplined academic writing overlap the habits of AI text on every detector. That's the false-positive problem in one sentence. Scan the same essay here: if our per-line view shows nothing concrete, that disagreement is itself useful evidence for your conversation.