UD5 Toolkit
Font Loading API Demo - Online Wait for Fonts Ready
Use the document.fonts API to check if a font is loaded. Watch the ready promise. Avoid FOUT. JavaScript demo.
Tag: API Request Builder
63+ toolsNavigation Timing API Viewer - Online Page Load Breakdown
See your current page load broken down into DNS, TLS, request, and DOM phases. Understand where time is spent.
Browser Feature Support Detector - Online Check Your Device
See a comprehensive table of which modern web APIs your current browser supports. Includes WebGPU, AVIF, and more.
FedCM Demo - Online Federated Credential Management
Experiment with the Federated Credential Management API. Simulate a sign‑in flow without third‑party cookies. Privacy‑first.
Resource Timing Viewer - Online See All Asset Loads
List all resources loaded by the current page and their detailed timing breakdown. In‑browser waterfall.
Selection & Range API Demo - Online Get/Set Selection
Select text and see the Selection object properties. Create ranges programmatically. Understand how rich‑text editors work.
Permissions Query API Demo - Online Check All APIs
Query the permission state of camera, microphone, geolocation, and more. See the response and learn the API.
Get Installed Related Apps Demo - Online PWA Detection
Check if your related native or PWA app is installed. See the API in action and copy the code.
Web USB Console - Online Claim & Talk to USB Device
Request a USB device and communicate with it using the Web USB API. See vendor and product IDs. Experimental.
Web HID Explorer - Online List & Read HID Devices
Request HID devices and list them. Read input reports and send output. For custom hardware and controllers.
Web Serial Terminal - Online Connect to Microcontroller
Connect to a serial device (Arduino, etc.) via the Web Serial API. Send and receive text. No native app needed.
Contact Picker API Demo - Online Select & Read Contacts
Pick a contact from the device’s address book (mobile). Read name, email, and phone. All permission‑based. Privacy safe.
Navigation API Playground - Online Single‑Page Router
Intercept and manage navigations without reloading. Test transition handling and URL updates. The future of client‑side routing.
File Handle API Demo - Online Persistent File Access
Use the File System Access API with file handles for persistent read/write. Learn incremental saving patterns.
Content Indexing API Test - Online Add to Device's Media Feed
Test the Content Indexing API to add a page to the device's content feed. See how your PWA integrates with the OS.
Broadcast Channel API Demo - Online Cross‑Tab Communication
Open the same page in two tabs and send messages between them. See real‑time cross‑tab communication. Learn the API.
API Request Builder - Online Test REST Endpoints
Select HTTP method, set headers, and body. Send requests and see the full response. Lightweight Postman alternative.
Navigation Timing API Viewer - Online Page Load Breakdown
See your current page load broken down into DNS, TLS, request, and DOM phases. Understand where time is spent.
Shared Storage API Demo - Online Cross‑Site Data
Write to shared storage and run a worklet to process data. Learn the privacy‑preserving alternative to third‑party cookies.
Media Session API Demo - Online Now Playing Widget
Set media metadata and play/pause controls for the OS media widget. Test action handlers. Perfect for web audio apps.
EyeDropper API - Online Pick Any Screen Color
Use the EyeDropper API to sample a color from anywhere on your screen. Click, select, and copy the hex. No extensions needed.
Prioritized Task Scheduler Demo - Online scheduler.postTask()
Schedule tasks with user‑visible, user‑blocking, or background priority. See execution order and delays. Modern web perf.
File System Access API Demo - Online Open & Save Files
Test the modern File System Access API. Open a file, modify it, and save back to disk. All sandboxed in browser.
Launch Handler API Demo - Online Control App Launch Behavior
Configure how your PWA launches: focus existing or create new. Test with the launch_handler manifest field.
Constraint Validation API Tester - Online Form Debug
Test required, pattern, minlength etc. See validity states and custom error messages. Learn browser‑native validation.
Web Animations API Sandbox - Online JS Animation Editor
Write JavaScript using element.animate() and see the result in a live preview. Compare with CSS keyframes. Debugger included.
Private State Token Demo - Online Anti‑Fraud Test
Issue and redeem Private State Tokens (formerly Trust Tokens). Understand how they help detect bots without cookies.
Web Share Level 2 Tester - Online Share Files
Test sharing multiple files (images, PDFs) using the Web Share API. Check if the browser supports file sharing. Demo page.
Picture‑in‑Picture Tester - Online Float Video Anywhere
Open a test video in Picture‑in‑Picture mode. Control entering and leaving PiP. Copy the code snippet for your own app.
Bluetooth Battery Monitor - Online Read Device Levels
Connect to a BLE device and read its Battery Service characteristic. See the charge level in a gauge.
Ambient Pressure Sensor Demo - Online Barometer
Read the ambient atmospheric pressure in hPa using the Pressure Sensor API (if available). Real‑time graph.
Linear Acceleration Sensor - Online Motion Visualizer
Visualize real‑time linear acceleration (excluding gravity). Watch the 3D vector graph move as you shake the device.
Web OTP API Demo - Online Auto‑Read SMS Codes
Demonstrate how the Web OTP API automatically reads one‑time codes from SMS (mobile). Simulation with a fake SMS input.
Font Access API - Online Browse Local Fonts
Enumerate all fonts installed on your device and see a real‑time preview. Useful for design tools. Permission required.
Wake Lock API Tester - Online Prevent Screen Sleep
Request and release a screen wake lock to keep the device awake. See the lock state in real time. Perfect for recipes or presentations.
Compression Streams API Demo - Online Gzip/Deflate Raw
Compress and decompress text using the browser's native Compression Streams API. See the binary output size.
Gamepad Tester - Online Button & Axis Visualizer
Connect a game controller and see every button press, axis movement, and vibration test. Uses the Gamepad API.
Mutation Observer Tester - Online DOM Change Watcher
Modify the DOM via buttons and see MutationRecords logged. Understand childList, attributes, and subtree options.
Resize Observer Playground - Online Watch Element Size
Drag to resize a box and see the Resize Observer callback fire. Get contentRect and borderBoxSize. Learn the API.
Screen Wake Lock Tester - Online Keep Screen On
Toggle a screen wake lock to prevent the device from dimming or sleeping. See the lock state and learn the API.
Built-in Translation API Demo - Online On‑Device Translate
Test the experimental Translation API to translate text between languages directly in the browser, without cloud calls. Check support and copy the JavaScript starter.
Periodic Background Sync Registration - Online PWA Tool
Register a periodic background sync with a minimum interval. See the registration state and tags. Keep content fresh.
ImageDecoder API Demo - Online Progressive Decode
Decode an image progressively using the ImageDecoder API. See partial results and metadata. Modern alternative to <img>.
WebCodecs Video Frame Reader - Online Decode & Display
Decode individual video frames from a local file using the VideoDecoder API. Step through frames. Cutting‑edge browser feature.
Background Sync API Tester - Online Offline Queue
Register a one‑off background sync and see it fire when connectivity returns. Debug service worker sync logic.
Cookie Store API Tester - Online Async Cookie Read/Write
Read, write, and delete cookies using the modern Cookie Store API. Monitor change events. No more document.cookie parsing.
Web Notification Tester - Online Permission & Display
Check notification permission, request it, and send a test notification. Verify icon, body, and tag. Debug web push.
Network Information API Checker - Online Downlink Speed
Display your effective connection type (4g, 3g, etc.) and downlink speed using the Navigator API. Adapt your app accordingly.
Battery Status API Viewer - Online Check Level
See your device's battery level, charging status, and discharge time using the Battery Status API. Fun utility.
Screen Orientation API Tester - Online Lock & Check
Check current screen orientation and test the lock API. Useful for mobile web apps. Demo with code.
Pointer Events Playground - Online Mouse, Touch & Pen
Unified input demo: see pressure, tilt, and type from any pointer. Compare pointerType values. Essential for drawing apps.
Idle Detection API Demo - Online User Activity Monitor
Request permission and detect when the user is idle (away from keyboard). See screen lock state. For native‑like apps.
Gamepad API Tester - Online Visual Controller Check
Connect a gamepad and see all button presses and axis movements visually. Check that every input is detected correctly.
Web Locks API Demo - Online Resource Coordination
Acquire and release locks across tabs. Prevent race conditions in IndexedDB or localStorage. Visual queue and lock state.
Vibration API Demo - Online Test Haptic Feedback
Trigger different vibration patterns on mobile devices. Test if your phone supports haptic feedback. Simple demo.
API Status Checker - Online Test Endpoint & Response
Enter an API URL and quickly check its HTTP status code and response time. See response headers and body. Browser fetch.
View Transitions API Demo - Online Smooth Page Switch
See the View Transitions API in action. Cross‑fade and morph between two states. Copy the JavaScript starter code.
Web Share API Tester - Online Demo & Code
Test the Web Share API by sharing text, links, and files directly from the browser. Check compatibility and see example code.
HTTP Request Composer - Online Build & Send Requests
Pick a method, URL, headers, and body, then send an HTTP request directly from your browser. Debug APIs easily.
Clipboard API Tester - Online Read & Write Sandbox
Experiment with the Async Clipboard API: read/write text and images from the clipboard. Verify permissions and see demo code.