Backend

Reference backend implementations live in the server/ directory. They are not published packages — copy the code you need into your own backend project.

Directory	Framework	Port	Description
server/node	Express 5	3001	Node.js backend demo
server/java	Spring Boot 3	8080	Java backend demo
server/go	Gin	8082	Go backend demo

Quick Start (Node.js Demo)

cd server/node
pnpm install
pnpm dev

Server runs at http://localhost:3001. See each server directory's README for details.

API Endpoints

Method	Endpoint	Description
GET	/api/captcha	Generate captcha image
POST	/api/captcha/verify	Verify captcha
GET	/api/health	Health check
GET	/api/info	Server info

Generate Captcha

GET /api/captcha?type=slider&width=300&height=170

Parameter	Type	Default	Description
type	string	slider	Captcha type: slider or click
width	number	300	Image width
height	number	170	Image height
precision	number	5	Verification precision
clickCount	number	3	Click count (for click type)

Response (slider):

{
  "success": true,
  "data": {
    "captchaId": "uuid-string",
    "type": "slider",
    "bgImage": "data:image/png;base64,...",
    "sliderImage": "data:image/png;base64,...",
    "sliderY": 42,
    "width": 300,
    "height": 170,
    "expiresAt": 1700000000000
  }
}

Response (click) includes clickTexts and clickCharImages instead of sliderImage/sliderY.

Verify Captcha

POST /api/captcha/verify

Request body:

{
  "captchaId": "uuid-string",
  "type": "slider",
  "target": [123]
}

Response:

{
  "success": true,
  "message": "Verification successful",
  "data": { "verifiedAt": 1700000000000 }
}

Security Endpoints

Method	Endpoint	Description
GET	/api/security/status/:ip	Get IP security status
GET	/api/security/blacklist	Get blacklist entries
POST	/api/security/blacklist	Add IP to blacklist
DELETE	/api/security/blacklist/:ip	Remove IP from blacklist

Environment Variables

Variable	Default	Description
PORT	3001 (Node) / 8080 (Java) / 8082 (Go)	Server port
HOST	localhost	Server host
SECRET_KEY	captcha-pro-secret-key	AES-GCM encryption key
EXPIRE_TIME	60000	Captcha expire time (ms)
TIMESTAMP_TOLERANCE	60000	Timestamp tolerance (ms)

Frontend Integration

import { SliderCaptcha } from '@captcha-pro/core'

const captcha = new SliderCaptcha({
  el: '#captcha',
  verifyMode: 'backend',
  backendVerify: {
    getCaptcha: 'http://localhost:3001/api/captcha?type=slider',
    verify: 'http://localhost:3001/api/captcha/verify'
  },
  onSuccess: () => console.log('Backend verification passed!')
})

Per-Server Guides

• Node.js · Java · Go