20 tools
Website Performance & Accessibility Tools
Twenty tools to make pages faster and usable by everyone: Core Web Vitals budgets, LCP, INP and CLS analysis, waterfalls, bundles, fonts, images, caching, contrast, accessible names and keyboard access.
About these tools
Performance tools here work from evidence you can reproduce: a HAR file, a DevTools trace, the layout-shift and event-timing entries your own browser records, or the public HTML and response headers of a page. Each one says whether a figure is a field measurement, a lab measurement or a static estimate, because those are different things and are easy to confuse.
Accessibility tools separate what can be checked automatically from what needs a person. A clean automated result means no automated rule failed - it does not mean a page is accessible - so every audit ends with the manual checks that remain.
Popular tasks
All Website Performance & Accessibility Tools
- Core Web Vitals Budget Calculator Turn the documented LCP, INP and CLS thresholds into per-phase budgets for mobile and desktop, check measured p75 values against them, and see where the time has to come from.
- LCP Element Analyzer Identify the likely LCP element from a page's HTML or a pasted DevTools trace, split its time into TTFB, load delay, load duration and render delay, and get the specific fix for each.
- INP Interaction Profiler Analyse event timing entries or a DevTools trace to find the slowest interactions and split each into input delay, processing time and presentation delay - with lab and field kept apart.
- CLS Layout Shift Debugger Group layout-shift entries into CLS session windows, name the elements that moved, and flag likely causes - unsized media, late fonts, injected ads and banners.
- Resource Waterfall Analyzer Load a HAR file and see a waterfall of every request split into DNS, connect, TLS, wait and download, with blocking, priority, connection reuse and the slowest resources called out.
- Critical Request Chain Visualizer Derive dependency chains from a HAR file or a page's HTML and CSS - page, stylesheet, @import, font - measure each chain's cost and highlight the links you can break.
- JavaScript Bundle Analyzer Drop a bundle and its source map to see which packages and files make up its weight, find duplicated modules, and estimate compressed size - nothing is uploaded.
- CSS Coverage Analyzer Match a stylesheet's selectors against HTML to find rules that probably never apply, flag state and script-driven selectors as uncertain, and suggest critical-CSS candidates.
- Web Font Loading Optimizer Analyse @font-face rules or a page's fonts and get copyable CSS for font-display, preload, unicode-range subsets and size-adjusted fallbacks that reduce layout shift.
- Image Delivery Optimizer Check how a page delivers its images - format, transfer size, intrinsic versus displayed dimensions, lazy loading, priority and caching - and see the saving for each fix.
- Responsive Image srcset Builder Generate srcset, sizes and picture markup from your breakpoints and image widths, preview which file each viewport downloads, and copy framework-ready snippets.
- Preload and Preconnect Builder Generate preload, preconnect, dns-prefetch and modulepreload hints from the resources you name, with warnings for over-preloading, missing crossorigin and wrong as values.
- Browser Cache Policy Builder Build Cache-Control policies per resource type, simulate browser and CDN behaviour over time, and export Nginx, Apache, IIS and Express configuration.
- Compression Savings Estimator Compress your own CSS, JavaScript, HTML or JSON with gzip and deflate in the browser, optionally measure Brotli, and see realistic transfer savings per file.
- Third-Party Performance Budget Calculator Inventory analytics, ads, chat widgets and embeds, allocate byte, request and main-thread budgets to each, and produce a governance report that shows who is over.
- DOM Complexity Analyzer Measure element count, maximum depth and widest parents from HTML or a public URL, and find the repeated structures and hotspots that make the DOM expensive.
- HTML Semantic Outline Checker See a page's heading outline and landmark map, and find skipped levels, missing main or lang, and misused lists and tables - with corrected snippets.
- Accessibility Contrast Matrix Test every foreground and background in your palette, including hover and disabled states and translucent colours, against WCAG 2.2 text and non-text contrast thresholds.
- Accessible Name Debugger Paste an HTML component and see the accessible name and description each element receives, which rule produced it, and why aria-label, labels or content lost.
- Keyboard Navigation Auditor Audit a page's HTML for tab order, positive tabindex, unreachable controls, missing skip links and dialog focus problems, then walk the live checks in your own browser.
Newly added
Related A2Z.Tools utilities
- Cache-Control Checker
- HTTP Compression Checker
- Image Compressor
- HAR File Viewer
- Website Responsive Test
- Keyboard Checker
Other tool collections
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