Web Worker Fibonacci Demo - Online Non‑Blocking Calculation
Calculate large Fibonacci numbers in a Web Worker. See the UI remain responsive. Copy the pattern for your app.
UD5 Toolkit
Experience how the Web Locks API helps coordinate shared resources across tabs, windows, and workers — right in your browser.
Only one client can increment at a time – protected by a lock named 'my-shared-counter'.
No virtual clients yet. Add one to start testing the Web Locks API.
'my-shared-counter'.Calculate large Fibonacci numbers in a Web Worker. See the UI remain responsive. Copy the pattern for your app.
Generate a temporary webhook URL (mock) and view the JSON payloads sent to it. Great for testing integrations locally.
Enter a GraphQL endpoint, write a query, and see the response. Add headers and variables. Simple testing client.
Execute GraphQL queries against any endpoint with variables and headers. Explore schema via introspection. All requests made directly from your browser.
Enter processes and see how different scheduling algorithms handle them. Gantt chart generation. OS course helper.
Open many parallel WebSocket connections and send messages. Test your server's concurrency. All from your browser.
Generate random JSON data with customizable fields (users, products, orders). Useful for frontend mocking. All local.
Decode the header and payload of a JSON Web Token (JWT) without verifying the signature. Inspect claims securely on the client side. Great for developers.
Request notification permission and create a push subscription. See the subscription object. Learn how web push works.
Set a cron expression and see a calendar of the next 1,000 execution times. Never miss a schedule again.
Input any JavaScript object and see if structuredClone can deep‑copy it. Compare with JSON.parse/stringify. Learn transferables.
Describe cron schedule expressions in plain English and test future execution times. Indispensable for DevOps and backend developers. Local analysis.
Enter a CDN URL for a script or style and generate the integrity attribute with sha384 or sha512. Protect your site.
Build a GraphQL query by selecting fields and nesting visually. Copy the built query string. For learning and fast prototyping.
Create random strings of any length using custom character sets. Perfect for generating API tokens, salts, and unique codes. Fully client-side secure.
Watch a simulation of how the JavaScript event loop handles synchronous code, microtasks, and macrotasks. Learn async.
Experiment with the Federated Credential Management API. Simulate a sign‑in flow without third‑party cookies. Privacy‑first.
Build cron expressions using a visual editor with dropdowns. See human-readable description and next run times. Easier than raw cron.
Simulate paint colors on a pre-loaded room photo by adjusting hue, saturation. Find your perfect shade before buying. Local canvas.
Fill in a form to generate a valid package.json for your Node.js project. Includes popular scripts and fields. Local only.
Create a Review or aggregateRating structured data. Perfect for star ratings in search results. Copy the code.
Search and extract values from a large JSON object using dot/bracket notation. Quickly locate deeply nested fields. Data stays local in your browser.
Run the classic FizzBuzz with custom rules. See the output for any range. A beginner programmer's playground.
Combine a Pomodoro timer with a simple task list. Assign estimated Pomodoros to tasks and track completions. Boost focus and get things done.
Paste a JSON object and see a dynamic, draggable tree graph representation. Excellent for debugging nested data.
Assign an ICC profile to an image and simulate how it would look on another device. For accurate color workflows. Local.
Drag a battery, resistor, LED onto a grid and simulate current flow. Show Ohm's law in action.
Generate random icebreaker questions for meetings, parties, or classrooms. Categories for work, fun, and deep talks.
Click to build a laundry symbol and learn its meaning, or look up common symbols. Never ruin clothes again.
Generate an Article or BlogPosting structured data with headline, author, and image. For rich blog results.