CAPTCHA
Anti-Bot IntermediateWhat is CAPTCHA?
CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) is a challenge-response test designed to determine whether a user is human or a bot. The most common form asks users to identify distorted text, select images containing specific objects, or simply check “I’m not a robot.”
CAPTCHAs are the gatekeepers of the web. They’re everywhere — contact forms, login pages, checkout flows. While they protect against spam and brute-force attacks, they’re a major pain point for legitimate data operations.
Types of CAPTCHAs You’ll Encounter
| Type | Provider | Difficulty | Solve Method |
|---|---|---|---|
| Text-based | Legacy | Easy | OCR (Tesseract) |
| Image-based | reCAPTCHA v2 | Hard | Human solvers / ML |
| Invisible | reCAPTCHA v3 | Medium | Behavioral scoring |
| Privacy-focused | hCaptcha | Hard | Human solvers |
| Cloudflare | Turnstile | Medium | Browser fingerprinting |
reCAPTCHA v3 Example Flow:
1. User visits page → scores 0.1-1.0
2. Score < 0.5 → challenge triggered
3. Challenge: "Select all images with traffic lights"
4. Result: ✓ or ✗ based on accuracy
Pro insight: reCAPTCHA v3 doesn’t show challenges — it scores behavior. Run headless browsers with realistic mouse movements, typing patterns, and session durations to boost your score without solving explicit puzzles. For image challenges, 3rd-party solving services ($2-5/1000) offer human-powered accuracy when ML fails.