| name | seo-mobile |
| description | Audit mobile-friendliness of a page from the PageSnapshot — verify the viewport meta, no horizontal-scroll/fixed-width layouts, adequate tap targets, legible base font, and mobile/desktop content parity — and generate the viewport meta when missing. Module M7b. Feeds the Search SEO score. |
| allowed-tools | Read, Grep, Glob, WebFetch, Bash |
seo-mobile (M7b)
Google indexes mobile-first: the mobile rendering of a page is the canonical one for ranking. This module checks that a page is usable on a small viewport. Layout problems that hurt mobile usability often surface as CLS — cross-check references/cwv-thresholds.md.
Audits
Working from the PageSnapshot (rendered_dom if present, else raw_html):
- Viewport meta: a
<meta name="viewport"> exists with width=device-width and initial-scale=1. Flag missing, fixed-width (width=1024), or zoom-blocking (user-scalable=no, maximum-scale=1) values — the last also harms accessibility.
- No horizontal scroll: detect fixed-width containers / large absolute widths that force the viewport wider than the device (content overflowing a ~360 px small viewport).
- Tap-target size: interactive elements (links, buttons, form controls) should be large enough and spaced so adjacent targets are not easily mis-tapped.
- Legible base font: body text rendered at a readable base size, not a desktop-only small size that forces pinch-zoom on mobile.
- Content parity: the mobile DOM must contain the same primary content, headings, structured data, and links as desktop — mobile-first indexing ranks what is in the mobile render, so hidden/stripped mobile content is a ranking risk.
Fixes
- AUTO (
fixable: auto): inject <meta name="viewport" content="width=device-width, initial-scale=1"> into <head> when absent. Deterministic, additive, verifiable — emitted as a diff for fix.
- ADVISORY (
fixable: advisory): fixed-width/overflow layouts, tap-target sizing, base-font, and parity gaps depend on CSS, design system, and JS — high breakage risk. The tool diagnoses and prioritizes but does not auto-edit layout code. Never invent breakpoint values or pixel sizes — report observed values or leave a clearly-marked TODO for the user.
Verification
- Method
dom_assert: assert against the snapshot (viewport meta presence/content, computed widths, target geometry).
- Reproduce the deterministic part (viewport meta presence/content) offline:
node ${CLAUDE_SKILL_DIR}/../../scripts/parse-html.mjs --url <u> (or --file <path>) — inspect head_hygiene.viewport. Tap-target/overflow geometry is a manual_review pass over the rendered snapshot.
- Tap-target and overflow checks need the rendered snapshot (computed layout). When only
raw_html is available and layout cannot be resolved, status is needs_api, never a false pass.
Findings
Emit findings per schema/finding.schema.json. Examples:
M7b.viewport.missing — no viewport meta (status fail, severity 3, fixable: auto, axis search, confidence established).M7b.viewport.user_scalable_no — viewport disables zoom (status warn, severity 3, fixable: advisory, axis search, confidence established).M7b.layout.horizontal_scroll — content overflows the small viewport (status fail, severity 3, fixable: advisory, axis search, confidence directional).M7b.taptarget.too_small — interactive targets too small/close (status warn, severity 3, fixable: advisory, axis search, confidence directional).
Each finding: evidence.observed quotes the page (the meta tag string, the overflowing selector/width, the target geometry); verification.reproduce is the runnable command above; expected_impact is banded + confidence-tagged (no naked %).
Honesty
- Mobile-friendliness is a usability baseline, not a strong positive ranking lever — a fast, well-built desktop-only site does not get a ranking boost for adding a viewport tag; it removes a usability liability. Frame fixes as removing risk, not gaining rank.
- Google retired the standalone "Mobile-Friendly Test" tool and the page-experience badge; there is no single mobile-friendly ranking flag to "win." Don't ship that myth.
- A present viewport meta does not prove the layout is actually responsive — confirm with the rendered snapshot, don't infer responsiveness from the tag alone.
