Webpage Change Detection & Alerts with Google Suite and Hash Tracking

This n8n workflow monitors specified webpages for changes, tracks content hashes in Google Sheets, and sends email alerts via Gmail when a change is detected. It also stores the webpage content in Google Drive for historical reference.

What it does

This workflow automates the process of detecting changes on web pages and notifying you:

1. Schedules Checks: Periodically triggers to check for updates (e.g., every hour, daily).
2. Fetches Webpage Content: Makes an HTTP request to a configured URL to retrieve its HTML content.
3. Hashes Content: Calculates a SHA256 hash of the fetched HTML content to create a unique fingerprint.
4. Retrieves Previous Hashes: Reads existing webpage data (URL, last hash, last check date) from a Google Sheet.
5. Compares Hashes: Compares the newly generated hash with the previously stored hash for the same URL.
6. Detects Changes: If the hashes differ, it signifies a change on the webpage.
7. Alerts via Gmail: Sends an email notification with details about the changed webpage.
8. Stores New Hash and Content: Updates the Google Sheet with the new hash and the current timestamp, and saves the full HTML content of the changed page to Google Drive.
9. Removes Duplicates: Ensures that only unique URLs are processed and stored.

Prerequisites/Requirements

To use this workflow, you will need:

• n8n Instance: A running instance of n8n.
• Google Account: For Google Sheets, Google Drive, and Gmail.
• Google Sheets Credential: An n8n credential configured for Google Sheets access.
• Google Drive Credential: An n8n credential configured for Google Drive access.
• Gmail Credential: An n8n credential configured for Gmail access.
• Google Sheet: A Google Sheet set up to store your monitored URLs, their last checked hash, and last check date. The sheet should have columns like URL, Last Hash, Last Check.
• Google Drive Folder: A Google Drive folder where the HTML content of changed pages will be stored.

Setup/Usage

1. Import the Workflow:
   • Download the provided JSON file.
   • In your n8n instance, click "Workflows" in the left sidebar.
   • Click "New" -> "Import from JSON" and upload the downloaded file.
2. Configure Credentials:
   • Locate the "Google Sheets", "Google Drive", and "Gmail" nodes.
   • For each, click on the "Credential" field and select your existing Google OAuth2 credentials or create new ones if you haven't already. Ensure these credentials have access to Google Sheets, Google Drive, and Gmail respectively.
3. Configure Google Sheets Node:
   • In the "Google Sheets" node, specify the "Spreadsheet ID" and "Sheet Name" where your webpage data is stored.
   • Ensure the column names in your sheet match what the workflow expects (e.g., URL, Last Hash, Last Check).
4. Configure HTTP Request Node:
   • The "HTTP Request" node will dynamically fetch URLs from your Google Sheet. No manual configuration is typically needed here beyond ensuring it can access external websites.
5. Configure Crypto Node:
   • The "Crypto" node is set to use SHA256 hashing. No changes are usually required here.
6. Configure Gmail Node:
   • In the "Gmail" node, set the "To" email address for alerts.
   • Customize the "Subject" and "Body" of the email if desired, using expressions to include details like the changed URL.
7. Configure Google Drive Node:
   • In the "Google Drive" node, specify the "Folder ID" where the HTML content of changed pages should be saved.
8. Activate the Workflow:
   • Once all configurations are complete, click the "Activate" toggle in the top right corner of the n8n editor to start the scheduled checks.
   • Adjust the "Schedule Trigger" node to your desired interval (e.g., every 1 hour, every 24 hours).

This workflow will now automatically monitor your specified webpages and alert you to any content changes.