Responsive Design Emulator - Online Test All Device Sizes
See your website inside iframes at multiple breakpoints simultaneously. Side‑by‑side responsive testing.
UD5 Toolkit
A virtual flashlight transforms your device's screen into a powerful light source. By displaying bright colors at maximum screen brightness, it can illuminate dark spaces, serve as an emergency signal, or create ambient mood lighting. Unlike a physical flashlight, you can customize the color, brightness, and even add strobe effects — all directly from your browser with no app installation required.
Select Strobe mode to make the light flash at a customizable frequency (1–20 Hz). This is useful for parties, visual effects, or signaling attention. The SOS mode automatically flashes the international Morse code distress signal (three short, three long, three short flashes) — an essential feature for emergency situations. The Party mode smoothly cycles through vibrant colors for a dynamic light show.
Absolutely! The Virtual Flashlight is fully responsive and optimized for mobile devices. On smartphones, the light panel adjusts to a comfortable size, and you can tap it to enter fullscreen mode — turning your entire phone screen into a bright, uniform light source. It's perfect as a bedside light, reading lamp, or emergency flashlight when you need it most.
Fullscreen mode maximizes the light output by expanding the colored panel to cover your entire screen, eliminating distractions from controls and UI elements. This significantly increases the illuminated area and perceived brightness. Press F on your keyboard, tap the light panel, or click the Fullscreen button to activate it. Press Esc or tap again to exit.
The tool offers 10 carefully selected preset colors including Pure White (ideal for general illumination), Warm White (softer, eye-friendly for reading), Yellow, Orange, Red (great for preserving night vision), Pink, Purple, Blue, Cyan, and Green. You can also use the custom color picker to choose any color imaginable — millions of possibilities at your fingertips.
The Keep Screen On button attempts to use the browser's Wake Lock API, which prevents your device screen from dimming or sleeping while the flashlight is active. This feature requires a secure HTTPS connection and is supported on most modern browsers (Chrome, Edge, Safari on iOS 16.4+). If unsupported, we recommend manually setting your device's auto-lock/screen timeout to a longer duration in system settings.
Yes, completely free! There are no hidden costs, subscriptions, or account requirements. The tool runs entirely in your browser, with no data collection or advertisements. It works online and can also function offline once the page is loaded, making it a reliable companion for camping, travel, or emergency preparedness.
Definitely. The SOS mode is specifically designed for emergency signaling, flashing the universally recognized distress pattern. Combined with fullscreen mode at maximum brightness, your phone becomes a highly visible beacon. The strobe mode can also serve as a warning or attention signal. We recommend keeping this page bookmarked for quick access in unexpected situations.
See your website inside iframes at multiple breakpoints simultaneously. Side‑by‑side responsive testing.
Compare :focus and :focus‑visible styling. See which one applies when using mouse vs. keyboard. Accessible focus management.
Convert pixel values to viewport‑relative units (vw, vh, vmax, vmin) for a specified breakpoint. Includes DVH and SVH. Essential for fluid layouts.
Create a custom element with named slots and see content projection in action. Learn Web Components basics.
Play an audio file or use mic to see real‑time frequency bars. Choose colors. Great for music videos. Canvas.
Convert pixel values to viewport‑relative units (vw, vh, vmin, vmax) based on a selected breakpoint. Precise responsive design.
Adjust opacity visually with a slider and see the different CSS representations (opacity property vs RGBA/HSLA). Copy best option.
See a comprehensive table of which modern web APIs your current browser supports. Includes WebGPU, AVIF, and more.
Change the text input cursor color. See the effect live. Copy the minimal CSS. Simple but delightful.
Create a reflection effect for images or text using box‑reflect. Adjust direction and offset. Copy the CSS.
Drag a virtual ruler across your screen to measure pixel distances. Horizontal and vertical guides. Useful for UI designers checking alignment.
Generate a Lit Element web component skeleton with styles and properties. Copy and start coding immediately.
Record your screen, window, or tab with audio directly in the browser. Download the recording as a WebM file. No upload.
Record your screen, window, or tab with audio directly in the browser. Download as WebM. No extension required.
Register a service worker, subscribe to push, and send a test notification using a VAPID key pair. Step‑by‑step demo.
Convert pixel values to em and rem units based on a base font size. Bidirectional. Must‑have for front‑end developers.
Select any HTML element on a page and capture its screenshot. Download as PNG. Perfect for bug reports. JavaScript API demo.
Paste a user agent string to get a human-readable breakdown of browser, operating system, and device. See your own current agent info automatically.
Request a USB device and communicate with it using the Web USB API. See vendor and product IDs. Experimental.
Assign Secret Santa pairings from a list of names with spouse/partner exclusions. Optionally email results via mailto link. Fully local, no server.
Convert REM values to pixels and vice versa based on your root font size. Essential for scalable web typography.
Paste HTML and see a before/after comparison of minified output. Check the byte savings. All local.
Count total DOM nodes on the current page and show warnings if limits exceed best practices. Keep the DOM lean.
Virtual flip coins thousands of times and see the heads/tails ratio converge to 50%. Interactive law of large numbers.
Measure your browser's GPU compute power using a simple WebGPU matrix multiplication. See raw FLOPS and compare with peers. Fully client‑side.
Visualize audio in real time from your microphone or uploaded audio file. See the waveform dance. Uses Web Audio API locally.
Play left‑only, right‑only, and frequency sweeps to test your speakers or headphones. Quick audio check.
Generate a realistic, random user‑agent string for desktop, mobile, or bot. Perfect for API testing and scraping.
Build a properly formatted robots.txt file with user-agent rules and sitemap location. Validate syntax in real time. Essential for webmasters.
Tap a glass icon each time you drink a cup of water. See your daily intake. Reminders optional. Local storage.