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Browser Automation for Bulk PDF Download

Automating Complex Website Navigation to Download PDFs

Sometimes the data you need is locked behind login flows, multi-step navigation, dynamic pages, or implicit interactions that are difficult to script with simple HTTP requests. This solution demonstrates a controlled, auditable approach where a Python API accepts credentials, drives a headless browser to perform clicks and navigation (including unknown/variable pages), optionally surfaces CAPTCHAs for human solving, and downloads PDF artifacts from a government website at scale.

About the Solution

The Browser Automation service provides a secure API for delegated browser-driven scraping and downloads. Users provide a username and password through an authenticated backend API; the service launches an isolated headless browser session (Playwright or Selenium), performs the necessary clicks and navigation, handles dynamic content and async loading, and returns links or directly streams downloaded PDFs.

This use case focuses on lawful, permissioned access (for example, an account you own or with explicit consent). It is designed for scenarios like bulk retrieval of public records or forms that require authenticated access.

Core Capabilities

  • Credentialed login via secure API (no persistent user passwords stored).
  • Headless browser automation using Playwright or Selenium to perform clicks, form fills, and navigation across unknown pages.
  • Heuristics for locating download links or buttons and following redirect chains to actual PDF assets.
  • Automated CAPTCHA handling: detect CAPTCHA challenge and automatically solve it using an approved, auditable solver; can fall back to human-in-the-loop where required by policy.
  • Download batching, retry/backoff, and resumable downloads for large collections.
  • Logging, audit trails, and per-session isolation (temp profiles, ephemeral storage).

How It Works (High Level)

  1. Client requests a job and supplies ephemeral credentials via the secure API.
  2. Backend validates request and spins an ephemeral browser worker (Playwright recommended).
  3. Automation script performs login, navigates pages, follows links, and detects download targets.
  4. If a CAPTCHA is detected, the session automatically routes to an approved, auditable solver and logs the solver result. If policy requires, the session can fall back to pausing and notifying a human operator.
  5. PDFs are downloaded to an ephemeral storage location, scanned for viruses, and then packaged or uploaded to the client's storage endpoint.
  6. Session artifacts (logs, metadata, list of downloaded files) are returned to the client; credentials are discarded.

Typical Workflow

  1. Developer calls the API with job parameters (target site, username, password, selection filters).
  2. Worker performs the job and streams progress events (login success, page reached, files found, CAPTCHA encountered).
  3. On completion, worker returns download URLs or a ZIP of PDFs, plus a JSON manifest describing source pages and timestamps.

API Example (Python)

Below is a minimal example demonstrating how a client might submit credentials and start a job. The backend uses Playwright to run the browser task.

import requests

API_URL = "https://api.example.com/browser-job"

payload = {
    "target": "https://gov.example.gov/public-reports",
    "filters": {"year": 2023},
}

files = {}
headers = {"Authorization": "Bearer <YOUR_API_TOKEN>"}

# Credentials are sent in the JSON body over TLS; backend treats them as ephemeral.
resp = requests.post(API_URL, json={"username": "user@example.com", "password": "s3cr3t", **payload}, headers=headers)
print(resp.json())

Security, Compliance & Responsible Use

  • Legal & Terms: Only run against sites and accounts for which you have authorization. Scraping or automated access may violate terms of service or law — obtain consent when required.
  • Credential handling: Credentials are handled over TLS and never persisted beyond the job lifecycle. Prefer OAuth or API tokens when available.
  • CAPTCHA policy: The system automatically solves CAPTCHAs using an approved, auditable solver when enabled. Automated solving must only be enabled where explicitly permitted, logged, and auditable; otherwise the system falls back to human-in-the-loop.
  • Rate limiting: Workers implement polite crawling (rate limits, backoff) to avoid service disruption.
  • Malware scanning: All downloaded PDFs are scanned before delivering to clients.

Business Value

  • Save hours of manual downloads for regulatory, archival, or research purposes.
  • Consistent, auditable data collection with error handling and retries.
  • Safe delegation of credentialed access without exposing long-term secrets.

Getting Started

  1. Review the target site's terms and legal constraints.
  2. Create an API token and deploy the browser-worker service (Playwright recommended).
  3. Test with a single job and verify CAPTCHA auto-solve settings (or enable human-in-the-loop where required).
  4. Scale up with batching and monitoring once validated.

Example Outputs

  • JSON manifest with entries: {source_page, file_name, downloaded_at, sha256, size_bytes}
  • ZIP archive of downloaded PDFs or direct upload to client storage (S3/MinIO).