# Fast vs Deep Scan — Which AI Check to Use

Fast scan answers instantly and suits bulk checks. Deep scan runs every check we have — use it for grades, disputes and decisions. Both free.

- Source: https://scanforai.com/fast-vs-deep
- ScanForAI — AI-writing detection. A score is a signal, not a verdict.

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# Fast scan vs Deep scan. Pick deliberately.

Same scanner, two very different reads. **Fast** answers instantly and is built for quick looks and bulk. **Deep** runs **every check we have** and is the one to trust when the answer matters. Both are free.

## Deep for anything important. Fast for speed and volume.

If a result could touch a grade, a job, a dispute or a decision about a person — use Deep. If you need an instant first impression, or you are working through a stack of documents — Fast is what it is for, and its score tells you which ones deserve a Deep look.

|   | Fast scan | Deep scan |
| --- | --- | --- |
| **What runs** | The core pattern checks — sentence rhythm, phrasing, predictability, typography — combined by a trained scoring profile. | **Everything.** The full pattern set *plus* our trained deep-analysis model, run across every section of the document, with the strictest calibration we have. |
| **Speed** | **Instant.** Milliseconds of computing — which is also why it is unlimited. | A few seconds. Roughly a thousand times more computing per document. |
| **Accuracy** | A deliberate trade: tuned first to avoid flagging human writing, at the cost of catching less AI. A clean fast result is *not* a guarantee. | **Substantially more accurate** in both directions — catches far more AI *and* is far less likely to flag a person by mistake. |
| **Built for** | Quick looks. First passes. Checking a batch of entries fast. Deciding what deserves a closer read. | Grades, submissions, disputes, editorial calls, anything you might act on or show to someone else. |
| **How to read it** | As a **screening pass**: "clear", "worth a deep check", or "leaning AI". The middle answer is the honest one surprisingly often. | As our best read of the document — score, per-sentence marking, and the evidence behind every signal that fired. |
| **Price** | Free, no account, unlimited. | Free with a [free account](https://app.scanforai.com/register) — the account is the abuse guard, not a paywall. |

## Fast is tuned to be safely wrong, not confidently wrong.

Every detector makes mistakes. What you can choose is the *direction*. Our fast tier is tuned so that when it errs, it errs by saying "worth a deep check" — not by branding a person's writing as AI, and not by handing out clean bills of health it cannot back. That costs it raw catch-rate, and we would rather say so here than let a quick check be mistaken for a verdict. The Deep scan exists precisely so that being careful costs you nothing but a few seconds.