definitely-not-a-robot: Humanizing Browser Automation

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The Challenge

• Perfect timing: Bots click exactly 500ms after page load
• Linear movements: Mouse travels in straight lines to targets
• Consistent typing: Every keystroke at identical intervals
• Mechanical scrolling: Always the same speed and distance
• Zero mistakes: No hesitation, no errors, no human variability

• Testing tools getting blocked on production sites
• Web scraping for research hitting endless CAPTCHAs
• QA automation failing due to bot detection
• Monitoring tools getting IP banned
• Data collection becoming unreliable

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The Solution

1. Bezier curve mouse movements that arc naturally like a human hand
2. Variable typing speeds based on ASCII key distances
3. Random micro-movements during idle time
4. Natural hesitation before important clicks
5. Debug visualization to see exactly how the “human” moves

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Technical Build

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Core Architecture

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Key Implementations

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Bezier Mouse Movement Algorithm

// Splits long movements into segments with jitter
const distance = calculateDistance(start, end)
const segments = Math.max(2, Math.min(50, Math.floor(distance / 10)))

// Natural acceleration/deceleration
const speed = 0.03 + distance * 0.001
const acceleration = 0.002

// Bezier control points for curved paths
const ctrlPt1 = start + Math.random() * (end - start) * 0.5
const ctrlPt2 = end - Math.random() * (end - start) * 0.5

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ASCII-Based Typing Delays

// Larger key distance = longer delay
const diff = Math.abs(text.charCodeAt(i) - text.charCodeAt(i - 1))
const delay = averageDelayPerChar + (diff * 2)

// Pause after punctuation
if (['.', '!', '?'].includes(char)) {
  delay += 200 // Natural thinking pause
}

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Jitter Movement System

• 3-95 pixel random movements
• Returns to original position
• Simulates idle hand tremor
• Configurable intensity and count

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API Design

const browser = new HumanBrowser()

// All methods return promises for chaining
await browser.launch({ headless: false })
await browser.navigate('https://example.com')
await browser.humanMove('#button', {
  hesitationBeforeClick: true
})
await browser.humanType('Hello World', 100) // WPM
await browser.jitterMouse({ jitterCount: 3 })
await browser.wait(1000, 5000) // Random delay

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Results & Impact

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Technical Achievements

• Bezier curve paths instead of straight lines
• 50-150ms random click delays for natural hesitation
• WPM-based typing with variable speeds (default 40 WPM)
• Debug mode showing red path visualization
• Zero dependencies beyond Puppeteer ecosystem

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Real-World Usage

• QA Testing: Running tests on production without triggering bot detection
• Web Scraping: Collecting public data for research and analysis
• Automation: Building reliable workflows that don’t break
• Monitoring: Tracking competitor sites without getting banned

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Open Source Impact

• Published on npm as definitely-not-a-robot
• GitHub repository with working examples
• Demo automation of shadcn/ui interface
• Clear documentation and TypeScript types

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Lessons Learned

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Randomness is Key

• Humans don’t move in straight lines
• Typing speed varies based on key distance
• Everyone has idle hand movements
• Mistakes and corrections are natural

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Debug Visualization Matters

• See exactly how the mouse moves
• Verify Bezier curves look natural
• Spot mechanical patterns instantly
• Tune parameters visually

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Simplicity Wins

• Bezier curves for natural arcs
• Normal distribution for delays
• ASCII distance for typing variance
• Basic jitter for idle movement

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What Made It Work

1. Mathematical foundations — Bezier curves and easing functions
2. Observation of humans — How people actually move and type
3. Debug-first development — Visual feedback during creation
4. Modular design — Separate utilities for each behavior
5. TypeScript — Caught edge cases during development

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Industry Impact

• Proved simple randomization can defeat bot detection
• Showed legitimate use cases need human-like automation
• Demonstrated the importance of imperfection in automation
• Set a template for ethical automation tools

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Open Source

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Technologies Used

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Code Example

import HumanBrowser from 'definitely-not-a-robot'

const browser = new HumanBrowser()

await browser.launch({ headless: false })
await browser.navigate('https://ui.shadcn.com')

// Search with natural movement and typing
await browser.humanMove('input[type="search"]', {
  hesitationBeforeClick: true,
  debug: true // Shows red path
})
await browser.jitterMouse({ jitterCount: 3 })
await browser.humanType('Hello World', 86) // 86 WPM

// Navigate with pauses
await browser.wait(300, 500)
await browser.humanMove('button[aria-label="Select a team"]')

// Careful typing for important fields
await browser.humanType('Monster', 30) // Slow 30 WPM

await browser.close()

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Ethical Note