Skip to main content

BLS Captcha

BLS is a CAPTCHA type that presents a 3×3 grid of images with a numeric instruction code specifying which images to select. CaptchaAI analyzes each cell and returns the indices of tiles that match the instruction.

Overview​

BLS Captcha typically appears with:

  • A 3×3 grid containing 9 image cells
  • A numeric instruction code (e.g., 664, 123, 546) that specifies what to select
  • Returns an array of indices (1–9) of cells matching the instruction
  • Cells are numbered left-to-right, top-to-bottom
BLS Captcha Example

Example: A 3×3 BLS captcha asking to "select all boxes with number 664"

How to Solve BLS Captcha​

Step 1: Prepare the Grid Images and Instruction​

  • Extract all 9 images from the grid as separate images
  • Convert each image to Base64 data URI format: data:image/gif;base64,R0lGODlh...
  • Identify the numeric instruction code (e.g., 664, 123, 546)

The grid cells are numbered in reading order:

1 2 3
4 5 6
7 8 9

Step 2: Submit the Task to CaptchaAI​

Send a POST request to https://ocr.captchaai.com/in.php with all 9 images and the instruction code.

import requests

# Prepare the data
data = {
    'key': 'YOUR_API_KEY',
    'method': 'bls',
    'instructions': '664',
    'json': '1'
}

# Add all 9 base64 images
files = {f'image_base64_{i+1}': (None, images[i]) for i in range(9)}

response = requests.post('https://ocr.captchaai.com/in.php', data=data, files=files)
result = response.json()
task_id = result['request']

Step 3: Retrieve the Solution​

Wait 5 seconds, then poll for the result using a GET request to https://ocr.captchaai.com/res.php:

import time
import json

time.sleep(5)  # Wait 5 seconds

params = {
    'key': 'YOUR_API_KEY',
    'action': 'get',
    'id': task_id,
    'json': '1'
}

response = requests.get('https://ocr.captchaai.com/res.php', params=params)
result = response.json()

if result['status'] == 1:
    solution = json.loads(result['request'])  # e.g., [1, 4, 7, 8]
    print(f"Selected cells: {solution}")

Step 4: Apply the Solution​

The response contains an array of cell indices (1–9) that match the instruction. For example:

  • [1, 4, 7, 8] means cells 1, 4, 7, and 8 contain the matching pattern
  • Click or select these cells to complete the captcha

Response Format​

JSON Response (with json=1):

{
  "status": 1,
  "request": "[1, 4, 7, 8]"
}

Plain Text Response:

OK|[1, 4, 7, 8]

Common Errors​

  • ERROR_BAD_PARAMETERS: Missing images or invalid instruction format. Ensure all 9 images are provided as valid Base64 data URIs.
  • ERROR_ZERO_BALANCE: Insufficient account balance. Top up your account to continue.
  • CAPCHA_NOT_READY: Solution not ready yet. Wait 5 seconds and poll again.

For complete error documentation, see the Error Handling Guide.

Tips & Best Practices​

Tip: Always encode images as data URIs with the correct prefix: data:image/gif;base64, or data:image/png;base64,

Tip: Use json=1 parameter for structured responses that are easier to parse

Tip: Ensure the instruction code is numeric and matches the BLS system format

API Reference​

For complete API specifications and advanced options, visit the CaptchaAI API Documentation and select BLS Captcha from the sidebar.