# Detector & audit reference

> All 13 detectors, their thresholds, the audit check ids, and where to fix each.

All 13 detectors are enabled by default; toggle any of them via
`config.detectors` (see [The Engine](/docs/concepts/engine#configuration)). The
`Fix guide` column links to a fix guide for each — framework-specific where the
fix differs.

| Detector | What it catches | Threshold | Fix guide |
| --- | --- | --- | --- |
| `dom-bloat` | Excessive DOM nodes and deep nesting | ≥ 800 nodes (warning), ≥ 1,500 (error) | [Excessive DOM size](/fix/excessive-dom-size) |
| `duplicate-requests` | The same URL + method fetched repeatedly | 2+ identical requests within 2s | [Duplicate requests](/fix/duplicate-network-requests) |
| `console-spam` | High-volume console output | > 20 calls per 10s window | [Console log spam](/fix/console-log-spam) |
| `memory-leak` | Steadily growing JS heap without GC recovery | > 10% growth over 30s (warning), > 25% (error) | [Memory leak](/fix/memory-leak) |
| `layout-thrashing` | Clusters of layout shifts without user input | ≥ 3 shifts within 500ms | [Layout shift](/fix/cumulative-layout-shift) |
| `unoptimized-images` | Missing dimensions/lazy/alt, oversized, or distorted images | natural > 2× rendered; aspect mismatch > 0.15 | [Unoptimized images](/fix/unoptimized-images) |
| `large-images` | Oversized image transfers | ≥ 500KB (warning), ≥ 1,024KB (error) | [Large image files](/fix/large-image-files) |
| `long-task-attribution` | Scripts causing long animation frames (LoAF) | ≥ 3 long frames attributed to one source | [Long tasks](/fix/long-tasks) |
| `resource-bloat` | Oversized JS/CSS/font/image resources | ≥ 100KB (prod) / 500KB (dev) | [Large JS bundles](/fix/large-javascript-bundles) |
| `web-essentials` | Missing document essentials (favicon, viewport, lang, charset) | 4 document checks | [Web essentials](/fix/essentials) |
| `heavy-library` | Known heavy libraries and their pitfalls | 16 library signatures | [Heavy dependencies](/fix/heavy-dependencies) |
| `seo` | Discoverability / search-visibility problems | 20 checks (title ≤ 60, description ≤ 160 chars, …) | [Search visibility](/fix/seo) |
| `aeo` | AI answer-engine / agent readiness | 9 checks | [AI readiness](/fix/aeo) |

## Audit checks

The `seo`, `aeo`, and `web-essentials` detectors each emit one issue per failed
check. Each check id below is the value carried in the issue's `evidence.check`.

### Search visibility (`seo`) — 20 checks

Fix guides live under [/fix/seo](/fix/seo).

- `title-missing` — Missing page title
- `title-too-long` — Page title is too long
- `title-default` — Page title is a framework default
- `meta-description-missing` — Missing meta description
- `meta-description-too-long` — Meta description is too long
- `og-image-missing` — Missing social preview image (og:image)
- `og-title-missing` — Missing og:title
- `og-description-missing` — Missing og:description
- `canonical-missing` — Missing canonical link
- `h1-missing` — No <h1> heading
- `h1-multiple` — Multiple <h1> headings
- `image-alt-missing` — Images missing alt text
- `slug-unfriendly` — Unfriendly URL slug
- `noindex` — Page is set to "noindex"
- `title-too-short` — Page title is very short
- `og-url-missing` — Missing og:url
- `twitter-card-missing` — Missing Twitter/X card
- `generic-link-text` — Vague link text
- `sitemap-missing` — Missing or invalid sitemap.xml
- `robots-missing` — Missing robots.txt

### AI answer-engine readiness (`aeo`) — 9 checks

Fix guides live under [/fix/aeo](/fix/aeo).

- `structured-data-missing` — No structured data (JSON-LD)
- `structured-data-invalid` — Structured data is invalid
- `no-main-landmark` — No <main> landmark
- `no-author-metadata` — No author or date signals
- `llms-txt-missing` — No llms.txt
- `content-requires-js` — Content only renders with JavaScript
- `markdown-negotiation-missing` — No markdown content negotiation
- `ai-crawlers-blocked` — robots.txt blocks AI crawlers
- `mcp-discovery-missing` — No agent interface (MCP) advertised

### Document essentials (`web-essentials`) — 4 checks

Fix guides live under [/fix/essentials](/fix/essentials).

- `favicon` — Missing favicon
- `viewport` — Missing viewport meta tag
- `lang` — Missing lang attribute on <html>
- `charset` — Missing charset declaration

**Evidence shapes**

  Each issue carries a typed `evidence` object — e.g. `dom-bloat` emits
  `{ nodeCount, maxDepth, selector }`, `duplicate-requests` emits
  `{ url, method, count, windowMs }`. See `IssueEvidenceMap` in the
  [protocol types](/docs/reference/core-api#types) for the full per-detector map.