Every guide is mapped 1:1 to an active check key so you can move from warning to fix without guesswork.
Minification strips whitespace, comments, and unnecessary characters from code without changing functionality — typically saving 20-30% on file size. Every visitor downloads your development comments and formatting. Build tools like Terser (JS) and cssnano (CSS) handle this automatically, and most CDNs offer it as a toggle.
Open guideGoogle officially confirmed on March 12, 2024 that Core Web Vitals are used as a ranking factor (Google Search Central). After the March 2024 core update, sites with poor CWV experienced 20-40% traffic drops while those that improved saw 15-30% gains (BrightVessel). Pages at position 1 are 10% more likely to pass CWV than pages at position 9 (BKND).
Open guideBounce probability increases 32% when page load time goes from 1 to 3 seconds, and 123% at 10 seconds (Google/Huckabuy). Conversion rates drop by 4.42% for each additional second of load time (WP Rocket). The average page loads in 2.5s on desktop but 8.6s on mobile (ToolTester, 2026) — meaning mobile users are already at the edge of abandonment before your page finishes.
Open guideBrotli compression reduces file sizes by up to 70% (vs Gzip's 65%), with Akamai reporting median savings of 82% for Brotli (DebugBear). Switching from Gzip to Brotli alone improves First Contentful Paint by approximately 3.5% (WP Rocket). Enabling compression is typically a single server configuration change that instantly benefits every visitor.
Open guideThis check measures how long the initial HTML document request takes. It is your baseline "first response" signal before all scripts, images, and secondary resources finish load...
Open guideImages comprise 21% of total webpage weight on average, with pages loading 4.4MB of image data (HTTP Archive, 2024). Only 30% of images are served in WebP format despite 97% browser support (W3Techs, 2026) — meaning most sites are still serving larger JPEG/PNG files when a smaller, identical-quality alternative exists. Switching to WebP typically cuts image bytes by 30-50%.
Open guideImages account for the largest portion of page weight on most sites — averaging 4.4MB per page (HTTP Archive, 2024). When total image bytes blow past your budget, mobile users on metered connections pay real money for your bloat, and everyone gets a slower experience. Performance budgets exist to catch this drift before it compounds.
Open guideRender-blocking resources are the most common cause of poor First Contentful Paint — only 68% of desktop pages and 51% of mobile pages achieve good FCP scores (Shopify Performance, 2024). Each render-blocking resource forces the browser to download and process it before painting any content. Inlining critical CSS and deferring non-critical scripts can make content appear seconds faster.
Open guideGoogle recommends a TTFB of 0.8 seconds or less, with 200ms as the ideal target (Seobility/Google). An analysis of 143,827 URLs found that TTFB was the strongest speed-related correlation with rankings (Neil Patel). TTFB is the foundation — no amount of frontend optimisation can overcome a slow server. Common causes: unoptimised database queries, no page caching, or inadequate hosting.
Open guideWhen interactive elements don't have accessible labels, screen readers announce them as "button" or "link" with no context — forcing blind users to guess what each control does. Notable accessibility settlements include Bashin's $2M settlement and accessiBe's $1M FTC settlement (Accessibility.Works, 2024). Proper ARIA labels are foundational accessibility requirements under WCAG 2.1.
Open guideApproximately 8% of males and 0.5% of females have colour vision deficiency — roughly 1 in 12 men worldwide (Vision Center). WCAG AA requires a minimum 4.5:1 contrast ratio for normal text. Low contrast also affects everyone reading on mobile screens in bright sunlight. With over 5,100 ADA web accessibility lawsuits filed in 2025 — a 20% increase from 2024 (EcomBack) — contrast failures are actionable legal risk.
Open guideWhen a label isn't programmatically associated with its input (via for/id or wrapping), screen readers don't announce what the field is for, and voice control users can't say "click email field." Form label errors are among the most commonly cited issues in accessibility audits, and they're straightforward to fix — just add matching for and id attributes.
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