blocks, parses the JSON, validates prerender/prefetch rules, eagerness levels, and URL predicate patterns. Chrome 121+ can instantly render next-page clicks.">

Speculation Rules API Audit

Speculation Rules are Chrome 121+ (Jan 2024) native prerendering — the next page is fully rendered in the background. Done right, link clicks feel instant. The audit checks your speculation rules JSON for shape and eagerness.

Context and background

Read the story behind this tool: Why Speculation Rules API Audit Exists →

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📖 Context & background

Read the story behind this tool: Why this tool exists — performance stack.

\n\n2. Use eagerness: "moderate" for prerender — Chrome prerenders on hover/focus.\n3. Use eagerness: "conservative" for prefetch — Chrome prefetches on mousedown / touchstart.\n4. Exclude URLs that are state-mutating (logout, delete, buy, auth). Use the "not" predicate.\n5. Exclude URLs likely to cause bandwidth / cost surprises (video pages, big-image pages) unless you have CDN bandwidth to spare.\n6. Test: in Chrome, open DevTools → Application → Speculative loads. Verify prerender runs on hover.\n7. If server-side logic relies on an HTTP request happening ONLY when user actually navigates, be aware: prerender hits your server early. Add Sec-Purpose: prefetch;prerender detection and avoid writes on those requests.\n8. For non-Chrome browsers: quicklink (https://github.com/GoogleChromeLabs/quicklink) is the polyfill.';const fp=(window.jwTool&&window.jwTool.enhancePrompt)?window.jwTool.enhancePrompt(fix,{persona:{role:'a senior front-end performance engineer',expertise:'Speculation Rules API (Chrome 121+), Sec-Purpose header, prerender vs prefetch tradeoffs, state-mutating URL exclusion',approach:'moderate-eagerness-first, exclude-mutating-urls, measure via DevTools Speculative Loads'},stakes:'Speculation rules can make navigation feel instant (0ms) but also waste bandwidth. Get eagerness + exclusions right.'}):fix;const sc=(window.jwAuditScorecard?window.jwAuditScorecard.render(findings,{title:'Speculation Rules',toolLabel:'Speculation'}):'');document.getElementById('results').innerHTML=sc+'

Findings

'+findings.map(renderChk).join('')+'

'+(scripts.length?'

Current speculation rules

'+esc(scripts.map(s=>s.raw).join('\n\n'))+'

':'')+'

Fix prompt

'+esc(fp)+'

';document.getElementById('results').style.display='block';try{window.jwAugmentCheckLinks&&window.jwAugmentCheckLinks({rootSelector:'#results',targetUrl:url});}catch(_){}}catch(e){document.getElementById('results').innerHTML='

Audit failed: '+esc(e.message)+'

';document.getElementById('results').style.display='block';}finally{document.getElementById('loading').style.display='none';}});