UD5 Toolkit
Interactive sandbox to understand LCP, INP, and CLS. Tweak parameters, observe real-time impact, and learn optimization strategies.
Click the button to measure INP.
Inject content to see layout shift impact.
<link rel="preload">requestAnimationFrame for visual updateswidth & height on imagesmin-height for async content areas<link rel="preload" as="image">, (3) Compress images to WebP/AVIF format, (4) Remove render-blocking JavaScript and CSS, (5) Ensure the LCP element is not lazy-loaded, and (6) Use efficient caching strategies.setTimeout or requestAnimationFrame to yield to the browser, (3) Debounce or throttle rapid events like scroll and resize, (4) Offload CPU-intensive work to Web Workers, (5) Avoid synchronous layout reads/writes that cause forced reflows.min-height, (3) Web fonts causing FOIT/FOUT — use font-display: swap with a fallback font that matches the size, (4) Content injected above existing content — prefer appending below the fold.Enter a URL and get a quick simulation of First Contentful Paint, LCP, and CLS using browser metrics. Lightweight alternative.
Patch the PerformanceObserver and show your page’s Core Web Vitals as you browse. See real‑time scores and suggestions.
Type a UPC or EAN number and see how a laser scanner would identify it, plus check digit validation.
Ask a yes/no question and click to reveal a classic Magic 8-Ball response. Animated shake effect. Nostalgic fun, pure local randomness.
Set up resources and processes and run the Banker's algorithm to check for safe states. Classic OS deadlock avoidance demo.
Simulate memory page reference strings with FIFO, LRU, and Optimal algorithms. See page fault count. OS concept demo.
Render 1000 styled elements using inline styles vs. CSS classes and compare time. Understand CSS‑in‑JS trade‑offs.
Enter a password and see the estimated time it would take to crack using brute force at different speeds. Educational.
Test a regex against long strings and measure execution time. Detect catastrophic backtracking patterns. Visual warning if slow.
Open many parallel WebSocket connections and send messages. Test your server's concurrency. All from your browser.
Measure your browser's GPU compute power using a simple WebGPU matrix multiplication. See raw FLOPS and compare with peers. Fully client‑side.
Paste a raster image and an SVG, see the file size and rendering time. Understand when to use vector. Local.
Toggle contain: strict, content, paint, layout and see how it affects rendering. Understand isolation for faster pages.
Apply will‑change to any element and see its effect on compositing. Learn best practices for smooth animations.
Keep track of a tennis match: points, games, sets, and deuce. Supports tiebreak. Great for friendly matches. Local.
Upload any image and view it as a person with deuteranopia, protanopia, or tritanopia would. Promote inclusive design.
Roll any number of dice thousands of times and see a live bar chart of the sum distribution. Great for game designers.
Select functional groups to see an approximate IR absorption spectrum. Learn spectroscopy visually. All local.
Enter a URL and get a one‑page report of titles, description, headings, image alts, and broken links. All from browser.
Simulate random mouse moves, clicks, or keystrokes to test idle‑timeout logic. Stops when you move the mouse. Dev test.
Type any CSS selector with :hover/:active/:focus and see the styles applied live. Perfect for debugging interaction states.
Set a cron expression and see a calendar of the next 1,000 execution times. Never miss a schedule again.
Adjust ISO, aperture, and shutter speed sliders and see how it affects the exposure of a sample scene. Learn photography basics.
Select telescope and eyepiece parameters to see the field of view circle on a simulated night sky image.
Watch the planets orbit the Sun in a top‑down 2D view. Adjust speed and zoom. Distances not realistic; beautiful model.
Fold a virtual square paper step by step with crease lines and visual previews. Practice origami basics without wasting real paper. All canvas‑based.
Drag to see how a solar eclipse occurs. Visualize the moon's shadow. Educational and interactive.
Enter a URL and get a rough client-side performance simulation: request count, DOM size, and potential speed tips. No real Lighthouse.
Control a lunar module and try to land softly on the moon. Manage fuel and thrust. Classic arcade physics. Canvas.
Simulate how images and UI elements appear to users with various types of color blindness. Upload or paste image URL. Promote inclusive design.