CAPTCHA Glossary: Complete Developer Reference

Every CAPTCHA and anti-bot term a developer needs, in one place.

A

Action (reCAPTCHA v3): A label sent with reCAPTCHA v3 tokens identifying the user action (e.g., login, submit). Must match between site and API call.

API Key: Your unique authentication token for CaptchaAI. Used in every API request. Keep it secret; never commit to public repos.

Anti-bot: General term for systems designed to detect and block automated traffic. Includes CAPTCHAs, fingerprinting, and behavioral analysis.

B

Base64: Binary-to-text encoding used to transmit CAPTCHA images via API. Standard method for image CAPTCHA submission.

BLS CAPTCHA: Image grid CAPTCHA used primarily on BLS visa services. Solved via method=bls in CaptchaAI.

Bot Detection: Techniques sites use to distinguish bots from humans — browser fingerprinting, mouse movement tracking, timing analysis.

C

calc: CaptchaAI parameter that tells the solver to compute a math equation in a CAPTCHA image and return the result.

CAPTCHA: Completely Automated Public Turing test to tell Computers and Humans Apart. A challenge designed to block bots.

Challenge: A specific CAPTCHA instance presented to a user. In GeeTest, the challenge parameter is session-specific.

Cloudflare Challenge: Full-page Cloudflare protection requiring browser verification. Solved via method=cloudflare_challenge.

Cloudflare Turnstile: Cloudflare's invisible CAPTCHA replacement for reCAPTCHA. Solved via method=turnstile.

Callback: JavaScript function called when a CAPTCHA is solved. Must be triggered after injecting tokens in browser automation.

D

Data-sitekey: HTML attribute containing the CAPTCHA provider's site key. Used to identify the CAPTCHA on a page.

F

Fingerprinting: Collecting browser, device, and network attributes to create a unique identifier for a visitor.

G

GeeTest: Interactive CAPTCHA provider using slide, click, and icon challenges. Supported via method=geetest.

gt: GeeTest's account identifier parameter. 32-character hex string, constant per site.

H

HCAPTCHA: Privacy-focused CAPTCHA alternative by Intuition Machines. Uses image classification challenges.

Headless Browser: A browser without a visible GUI (e.g., headless Chrome). Used in automation but may be detected by anti-bot systems.

I

Image CAPTCHA: A CAPTCHA that displays distorted text or images requiring human interpretation. Submitted as base64 to CaptchaAI.

Invisible CAPTCHA: A CAPTCHA that runs without user interaction (e.g., reCAPTCHA v3, Turnstile managed mode).

J

JSON (response format): Setting json=1 in CaptchaAI requests returns structured JSON responses instead of plain text.

M

Method: CaptchaAI API parameter specifying the CAPTCHA type: userrecaptcha, turnstile, geetest, bls, base64, etc.

minLen / maxLen: Parameters constraining the expected length of an image CAPTCHA answer.

min_score: reCAPTCHA v3 parameter specifying the minimum acceptable score (0.0-1.0).

N

numeric: Image CAPTCHA parameter. 1 = digits only, 2 = letters only, 0 = no preference.

O

OCR: Optical Character Recognition. The process of reading text from images. CaptchaAI supports 27,500+ OCR CAPTCHA types.

P

pageurl: The full URL of the page displaying the CAPTCHA. Required for all token-based CAPTCHAs.

Polling: The process of repeatedly checking res.php for solve results. Standard interval: 5 seconds.

Proxy: An intermediary server used to route requests. CaptchaAI accepts proxy parameters for location-specific solving.

R

reCAPTCHA: Google's CAPTCHA system. Versions: v2 (checkbox/invisible), v3 (score-based), Enterprise.

reCAPTCHA Enterprise: Google's paid CAPTCHA with enhanced security features and API key authentication.

regsense: Image CAPTCHA parameter. 1 = case-sensitive answer required.

reportbad: CaptchaAI endpoint to report an incorrect solve. Helps improve model accuracy and may refund the solve.

res.php: CaptchaAI result polling endpoint. Returns CAPCHA_NOT_READY while solving, solution when complete.

S

Score (reCAPTCHA v3): A value from 0.0 (likely bot) to 1.0 (likely human) assigned by reCAPTCHA v3.

Sitekey: The public key identifying a site's CAPTCHA configuration. Extracted from HTML for API submission.

Stealth Mode: Browser automation techniques to avoid detection — modified navigator properties, realistic headers, etc.

T

Task ID: The identifier returned by in.php after submitting a CAPTCHA. Used to poll for results.

textinstructions: Image CAPTCHA parameter providing natural language hints to guide the solver.

Token: The CAPTCHA solution string. Must be injected into the page and submitted to the target site.

Token Expiry: How long a solved token remains valid. reCAPTCHA: 120s. Turnstile: 300s. Image: unlimited.

Turnstile: See Cloudflare Turnstile.

U

userrecaptcha: CaptchaAI method for all reCAPTCHA types (v2, v3, invisible, enterprise).

V

Validate / Seccode: GeeTest solution fields returned after solving. Must be submitted to the target site's validation endpoint.

Version: For GeeTest, specifies v3 or v4. For reCAPTCHA, v2 or v3.

Z

Zero-click CAPTCHA: A CAPTCHA that requires no explicit user action (e.g., Turnstile managed mode, reCAPTCHA v3).

Related Guides

• CAPTCHA Types Comparison Matrix
• CaptchaAI API Quick Reference

Learn the language of CAPTCHAs — start with CaptchaAI.