Google Sheets SSL Expiry Checker is a secure, free, and lightweight solution for checking SSL certificate expiry dates directly inside Google Sheets.
It is built with Google Apps Script on the frontend and a PHP API (MODX or standalone) on the backend.

✅ Manager-friendly — works directly in a Google Spreadsheet
✅ Secure by design — HMAC signature, HTTPS-only, timestamp validation
✅ Cache-enabled — reduces load and blocks spamming
✅ Flexible backend — works with MODX or any PHP hosting
✅ Free — no paid APIs or SaaS dependencies

1. Place the api.php script in your hosting root (can be MODX or pure PHP).
2. If using MODX:
   • Create a System Setting named ssl_checker_api_key and set your secret key.
   • Ensure $modx->cacheManager is available for caching.
3. If using standalone PHP:
   • Store $storedApiKey in a secure config file.
   • Replace MODX caching with file_put_contents() or any cache system.
4. Serve API only over HTTPS.

1. Open your Google Sheet.
2. Go to Extensions → Apps Script.
3. Paste the provided Google Apps Script code.
4. In the sheet, open the ⚙️ GM SCRIPTS menu and run SSL CHECKER.
5. Enter:
   • API URL (https://yourdomain.com/api.php)
   • API Key (from backend)
   • Column with domains
   • Column to update with expiry dates
6. Done ✅ — all expiry dates will be fetched securely.

• HTTPS-only — request rejected if not over TLS
• HMAC SHA256 — verifies request authenticity
• Timestamp validation (±30s) — blocks replay attacks
• Server-side cache (60s default) — reduces load & spam
• Minimal exposed surface — only one POST endpoint
• Maxum post content size — is 500 KB

• 🕒 Saves hours — no manual SSL checks
• 📊 Centralized view of certificate expiry dates
• 🔐 No public API leakage
• ⚡ Fast due to caching

MIT — free to use, modify, and integrate.

⭐ If this tool saved you time — give it a star on GitHub and share with your colleagues!