Monitoring 101: Essentials
Monitoring watches site health 24/7. Critical for users, revenue.
Compare tools: Best 2025. Setup: Get Started.
What
Continuous checks: Accessible, functional, performing.
Example: E-comm: Homepage loads, cart adds, checkout works. Alert on fail.
Monitoring vs Perf
Monitoring: Up/down? Perf: How well?
Need both: Up but slow loses users.
Pro tip: Start monitoring, add perf.
Uptime vs Availability
Uptime: Operational time %. Availability: Operational probability, includes maintenance.
| % | Mo Down | Yr Down | Impact |
|---|---|---|---|
| 90 | 72 hrs | 36.5 days | Bad |
| 95 | 36 hrs | 18.25 days | Poor |
| 99 | 7.2 hrs | 3.65 days | Ok |
| 99.9 | 43 min | 8.77 hrs | Good |
| 99.99 | 4 min | 52 min | Excellent |
| 99.999 | 26s | 5 min | World-class |
99% = weekend down. Not great.
Metrics
HTTP codes: 200 good, 3xx ok, 4xx client err, 5xx server err.
Response: <200ms target, <1s acceptable, >3s bad.
Uptime: 99.9% min.
Geographic: Diff regions.
SSL: Expiry 30+ days warn, handshake <100ms, chain valid.
Content: Keywords present, API expected, forms work.
Advanced: TTFB, Web Vitals, synthetic, RUM.
Deep dive: Real-time vs 5-min. Landscape: Intro.
Types
- Ping: Alive?
- HTTP/S: Server response.
- API: Endpoints valid.
- Transaction: Full flows.
- DNS: Resolution.
Practices
- HTTP main pages.
- Alerts.
- Multi-locations.
- Test alerting.
Strategy:
Critical: Homepage, login, checkout, API, admin.
Frequency: Critical 1 min, important 5 min, secondary 15 min.
Thresholds: Response 3x normal, immediate downtime, content missing.
Response: Who alerted, escalation, tracking.
Avoid Mistakes
- Alert fatigue: Tune thresholds.
- One location: Multi-region.
- Ignore SSL: Monitor expiry.
- No full journey: Multi-step.
- Forget mobile: Monitor specific.
- No doc: Document setup/response.
Advanced: Beyond Uptime, Best Practices.
Why exit1.dev
30s checks free, dev-friendly, global, intelligent, transparent.
Conclusion
Monitor smart. Start simple, evolve.
Sign up free. Catch issues before users.
Related: Get Started, Free Tools, Downtime, Free vs Paid, Best Practices
Sources
- MDN: HTTP response status codes — https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Status
- web.dev: Core Web Vitals — https://web.dev/articles/vitals
- Google SRE Book: Monitoring Distributed Systems — https://sre.google/sre-book/monitoring-distributed-systems/
Recommended Free Monitoring Resources
- Free Uptime Monitor Checklist – Step-by-step actions to configure a free uptime monitor that catches incidents fast.
- Best Free Uptime Monitoring Tools (2025) – Compare the strongest free uptime monitor platforms and when to upgrade.
- Free Website Monitoring Tools 2025 Guide – Evaluate which free website monitor fits your stack and alerting needs.
- Free Website Monitoring for Developers – See how engineering teams automate alerts, SLO tracking, and reporting with a free website monitor.
Morten Pradsgaard is the founder of exit1.dev — the free uptime monitor for people who actually ship. He writes no-bullshit guides on monitoring, reliability, and building software that doesn't crumble under pressure.