Lazy Loading Image Snippet Generator - Online
Generate an <img> tag with the loading='lazy' attribute and optional low‑quality placeholder. Improve Core Web Vitals. Copy the snippet.
UD5 Toolkit
Generate optimized <link> tags for preload, prefetch, preconnect and dns-prefetch to speed up your website.
<link> elements that tell the browser to perform early actions (like DNS lookups, TCP handshakes, or pre-fetching) before they are strictly needed. They help improve perceived page load performance by warming up connections or preloading critical assets.
crossorigin="anonymous" (or use-credentials) to match the eventual request. Otherwise the browser may fetch the resource twice, wasting bandwidth.
preconnect to a CDN origin combined with a preload for a specific font file from that CDN. Avoid redundant hints, though; a single preconnect already covers DNS resolution, making an extra dns-prefetch unnecessary.
preload, prefetch, preconnect, and dns-prefetch. However, always check caniuse.com for the latest compatibility details, especially for preload nuances.
Generate an <img> tag with the loading='lazy' attribute and optional low‑quality placeholder. Improve Core Web Vitals. Copy the snippet.
Select a caching strategy and see a flow diagram of how requests are handled. Learn PWA patterns.
Generate a complete <head> section with meta charset, viewport, SEO, favicon, and social tags. Customize and copy.
Schedule tasks with user‑visible, user‑blocking, or background priority. See execution order and delays. Modern web perf.
Run a CPU‑heavy calculation (e.g., prime numbers) in a Web Worker and see the UI stay responsive. Code snippet provided.
Display used/total/limit JS heap size using performance.memory. Take snapshots and see growth. Simple memory leak detection.
Learn how to register your PWA to handle custom URL protocols. See the manifest entry and test.
Render 1000 styled elements using inline styles vs. CSS classes and compare time. Understand CSS‑in‑JS trade‑offs.
Configure a modern HTML5 boilerplate with your choice of meta tags, social media cards, favicon links, and CSS/JS includes. Download or copy the code.
Apply content‑visibility: auto to off‑screen sections and see the rendering cost drop. Demos for infinite scroll optimization.
Toggle content‑visibility: auto on long blocks and see the rendering time difference. Understand this powerful property.
Configure how your PWA launches: focus existing or create new. Test with the launch_handler manifest field.
When a yarn is discontinued, find equivalent alternatives by matching weight and gauge. Local reference.
Write a generator function and step through it with next(). See values and done state. Understand iterators.
Choose a base style guide (Airbnb, Standard, Google) and add plugins. Generate a ready‑to‑use .eslintrc config.
Calculate large Fibonacci numbers in a Web Worker. See the UI remain responsive. Copy the pattern for your app.
See your current page load broken down into DNS, TLS, request, and DOM phases. Understand where time is spent.
See your current page load broken down into DNS, TLS, request, and DOM phases. Understand where time is spent.
Compress text with Brotli at different quality levels. See size reduction and time. Find the sweet spot for your static assets.
See how many tabs you have open and estimate memory usage based on navigator object. Fun productivity check.
Create a properly styled 'Skip to Content' link. Customize target and appearance. Essential for keyboard users. Copy the HTML/CSS.
List cached responses for your domain. View headers, content, and delete individual entries. Understand your PWA's cache.
Enter income, pay frequency, and expected deductions to estimate your tax refund or balance due. Simplified model.
Fill in your PWA details to generate a valid manifest.json file. Include icons, theme color, display mode.
Fairly distribute pooled tips among staff based on hours worked or points. Customizable percentages. All calculations local and private.
Place rectangular pattern pieces on a virtual fabric width to optimize cutting layout and reduce waste. Simple manual drag & drop. Local only.
See the View Transitions API in action. Cross‑fade and morph between two states. Copy the JavaScript starter code.
Create CSS mask‑image effects with custom shapes, gradients, and SVGs. Visually see the mask applied to an image. Copy the CSS.
Adjust root, margin, and threshold. See a live log of intersection events as you scroll. Debug lazy loading.
Write text with inline footnote markers and this tool will move the notes to the bottom and add proper Markdown links. Saves time.