Solve BLS CAPTCHA with Node.js and CaptchaAI

BLS CAPTCHA presents a 3×3 grid of images with a numeric instruction code specifying which cells to select. This tutorial shows you how to solve BLS CAPTCHAs from Node.js using the CaptchaAI API.

Prerequisites

Item	Value
CaptchaAI API key	From captchaai.com
Node.js	14+
Library	`axios` (`npm install axios`)

How BLS CAPTCHA works

A 3×3 grid numbered left-to-right, top-to-bottom:

1 | 2 | 3
---------
4 | 5 | 6
---------
7 | 8 | 9

A numeric instruction (e.g., "664") specifies what to select. CaptchaAI returns the indices of matching cells.

Step 1: Extract grid images

const axios = require('axios');
const puppeteer = require('puppeteer');

const browser = await puppeteer.launch();
const page = await browser.newPage();
await page.goto('https://example.com/bls-form');

// Get instruction code
const instruction = await page.$eval('.bls-instruction', (el) => el.textContent.trim());

// Get all 9 cell image URLs and convert to base64
const cellImages = await page.$$eval('.bls-grid img', (imgs) =>
  imgs.map((img) => img.src)
);

const images = [];
for (const src of cellImages) {
  if (src.startsWith('data:')) {
    images.push(src);
  } else {
    const { data } = await axios.get(src, { responseType: 'arraybuffer' });
    const b64 = Buffer.from(data).toString('base64');
    images.push(`data:image/png;base64,${b64}`);
  }
}

Step 2: Submit to CaptchaAI

const API_KEY = 'YOUR_API_KEY';
const sleep = (ms) => new Promise((r) => setTimeout(r, ms));

const params = new URLSearchParams({
  key: API_KEY,
  method: 'bls',
  instructions: instruction,
  json: '1',
});

// Add all 9 images
images.forEach((img, i) => {
  params.append(`image_base64_${i + 1}`, img);
});

const { data: submitData } = await axios.post(
  'https://ocr.captchaai.com/in.php',
  params.toString()
);

if (submitData.status !== 1) throw new Error(submitData.request);
const taskId = submitData.request;
console.log(`Task submitted: ${taskId}`);

Step 3: Poll for the solution

await sleep(5000);

let selectedCells;
for (let i = 0; i < 30; i++) {
  const { data: pollData } = await axios.get('https://ocr.captchaai.com/res.php', {
    params: { key: API_KEY, action: 'get', id: taskId, json: 1 },
  });

  if (pollData.status === 1) {
    selectedCells = JSON.parse(pollData.request);
    console.log('Selected cells:', selectedCells);
    break;
  }
  if (pollData.request !== 'CAPCHA_NOT_READY') {
    throw new Error(pollData.request);
  }
  await sleep(5000);
}

Step 4: Click the correct cells

// Click each identified cell
const gridCells = await page.$$('.bls-grid img');
for (const cellNum of selectedCells) {
  await gridCells[cellNum - 1].click();
}

// Submit the form
await page.click('.bls-submit');
console.log(`Solved: clicked cells ${JSON.stringify(selectedCells)}`);
await browser.close();

Expected output:

Selected cells: [1, 4, 7, 8]
Solved: clicked cells [1,4,7,8]

Common errors

Error	Cause	Fix
`ERROR_BAD_PARAMETERS`	Missing images or instruction	Send all 9 images and the instruction code
`CAPCHA_NOT_READY`	Still processing	Keep polling every 5 seconds
`ERROR_ZERO_BALANCE`	No funds	Top up your CaptchaAI account