UD5 Toolkit
Barcode Scanner Simulator – Online Enter Number & Visualize
Type a UPC or EAN number and see how a laser scanner would identify it, plus check digit validation.
Tag: Simulator - Virtual Testing
40+ toolsSimple Circuit Simulator – Online Visual Resistor LED
Drag a battery, resistor, LED onto a grid and simulate current flow. Show Ohm's law in action.
Browser Console Simulator - Online Practice JavaScript Logging
Type JavaScript expressions and see output like a real browser console. Supports console.log, error, warn. Use for quick testing without DevTools.
Viewport Meta Tag Simulator - Online Test Mobile Rendering
Change the viewport meta tag and see how a page would render at different device widths. Understand responsive basics.
Gradient Color Blindness Simulator - Online Test Palettes
Upload a gradient or enter a palette and simulate how it appears with different types of color vision deficiency. Ensure inclusive data visualization.
Paper Snowflake Simulator - Online Fold & Cut Preview
Virtually fold a digital paper and cut out shapes to see a snowflake unfold. Experiment with designs before real scissors. Pure creative fun.
Two‑Pass Assembler Simulator - Online Simple SIC/XE
Write a simple assembly program and see the pass‑1 and pass‑2 symbol tables and object code. Systems programming helper.
CPU Scheduler Simulator - Online FCFS, SJF, Round‑Robin
Enter processes and see how different scheduling algorithms handle them. Gantt chart generation. OS course helper.
Print Contrast Simulator - Online See How It Looks on Paper
Upload an image and see a rough simulation of how it might look when printed. Highlights areas that may lose detail.
Adaptive Bitrate Streaming Simulator - Online HLS/DASH Demo
Simulate adaptive bitrate logic by switching between different quality video segments. See how ABR algorithms work.
Telescope Field of View Simulator – Online Eyepiece & Object
Input telescope and eyepiece parameters to see a simulated view of the Moon or Andromeda. Plan observations.
Exposure Triangle Simulator – Online ISO, Aperture, Shutter
Adjust ISO, f‑stop, shutter speed and see a simulated image brightness and depth of field effect. Learn manual mode.
Banker's Algorithm Simulator - Online Deadlock Avoidance
Set up resources and processes and run the Banker's algorithm to check for safe states. Classic OS deadlock avoidance demo.
Brute Force Time Estimator - Online Password Cracking Simulation
Enter a password and see the estimated time it would take to crack using brute force at different speeds. Educational.
SQL Injection Simulator - Online Educational Sandbox
Test SQL injection inputs on a mock database and see the resulting query. Learn how to prevent SQLi. No real data.
Screen Reader Text Simulator - Online See What It Says
Enter an HTML snippet and see a rough transcription of what a screen reader might announce. Check alt texts.
Magic 8-Ball Simulator - Online Ask and Shake
Ask a yes/no question and click to reveal a classic Magic 8-Ball response. Animated shake effect. Nostalgic fun, pure local randomness.
Page Replacement Simulator - Online FIFO, LRU, Optimal
Simulate memory page reference strings with FIFO, LRU, and Optimal algorithms. See page fault count. OS concept demo.
Enhanced Color Blindness Simulator - Image & UI Combined
Upload an image and also see a UI mockup under different deficiencies side‑by‑side. Powerful for inclusive design.
Core Web Vitals Simulator - Online Learn How to Improve LCP/INP/CLS
Adjust page characteristics (image size, server delay, layout shift) and see the simulated Core Web Vitals scores. Understand what impacts performance.
Projectile Motion Simulator - Online Angle & Speed
Set launch angle, initial speed, and height. See the trajectory, max height, and range plotted on a canvas. Learn kinematics.
Tennis Scoring Simulator - Online Point Tracker
Keep track of a tennis match: points, games, sets, and deuce. Supports tiebreak. Great for friendly matches. Local.
WebSocket Load Tester - Online Simulate Many Clients
Open many parallel WebSocket connections and send messages. Test your server's concurrency. All from your browser.
Depth of Field Simulator - Online Blur Preview
Visualize how aperture, focal length, and subject distance affect background blur. Interactive DOF calculator.
Cron Job Simulator - Online Visual Schedule Tester
Set a cron expression and see a calendar of the next 1,000 execution times. Never miss a schedule again.
Steroids IR Spectrum Simulator - Online Simple Chemistry Tool
Select functional groups to see an approximate IR absorption spectrum. Learn spectroscopy visually. All local.
Camera Exposure Simulator - Online Learn ISO, Aperture, Shutter
Adjust ISO, aperture, and shutter speed sliders and see how it affects the exposure of a sample scene. Learn photography basics.
Dice Roll Simulator & Stats - Online Massive Roll Trials
Roll any number of dice thousands of times and see a live bar chart of the sum distribution. Great for game designers.
Random User Activity Simulator - Online Test Idle Logic
Simulate random mouse moves, clicks, or keystrokes to test idle‑timeout logic. Stops when you move the mouse. Dev test.
Paper Fold Simulator - Online Virtual Origami Practice
Fold a virtual square paper step by step with crease lines and visual previews. Practice origami basics without wasting real paper. All canvas‑based.
Hover State Simulator - Online Test :hover :active :focus
Type any CSS selector with :hover/:active/:focus and see the styles applied live. Perfect for debugging interaction states.
Lunar Lander Simulator - Online Retro Thrust Game
Control a lunar module and try to land softly on the moon. Manage fuel and thrust. Classic arcade physics. Canvas.
Solar System Simulator 2D - Online Top‑Down Orrery
Watch the planets orbit the Sun in a top‑down 2D view. Adjust speed and zoom. Distances not realistic; beautiful model.
Solar Eclipse Simulator - Online Visualize Totality
Drag to see how a solar eclipse occurs. Visualize the moon's shadow. Educational and interactive.
Color Blindness Simulator - Online Vision Deficiency Preview
Simulate how images and UI elements appear to users with various types of color blindness. Upload or paste image URL. Promote inclusive design.
Image Color Blindness Simulator - Upload & See
Upload any image and view it as a person with deuteranopia, protanopia, or tritanopia would. Promote inclusive design.
Telescope FOV Simulator - Online Eyepiece & View Preview
Select telescope and eyepiece parameters to see the field of view circle on a simulated night sky image.
Page Speed Simulator - Online Estimate Load Metrics
Enter a URL and get a rough client-side performance simulation: request count, DOM size, and potential speed tips. No real Lighthouse.
Online Dice Roller - Virtual Dice Simulator
Simulate rolling dice for board games, RPGs, and decision making. Choose number of dice and faces. Fun, lightweight, and no download required.
Coin Flipper - Online Heads or Tails Simulator
Flip a virtual coin to make a decision or settle a dispute. Realistic animation and fair random outcome. Simple, fast, and always available.