12 Common Causes of Website Downtime (And How to Prevent Each)

What Happens

Physical servers break. Hard drives fail, RAM corrupts, power supplies die. Cloud VMs can also experience underlying hardware issues. This is one of the oldest and most common causes of downtime.

Real-World Example

How to Prevent It

• Use redundant infrastructure (load balancers, multiple servers)
• Choose hosting with automatic failover
• Monitor server health metrics (CPU, memory, disk I/O)
• Keep backups current and tested

How Monitoring Helps

What Happens

Unexpected surge in visitors overwhelms the server. Can be caused by going viral on social media, a successful marketing campaign, a press mention, or a DDoS attack. The server runs out of resources (CPU, memory, connections) and starts returning errors or timing out.

Real-World Example

How to Prevent It

• Load test before launches
• Use auto-scaling infrastructure
• Implement caching (CDN, page cache, database query cache)
• Have a plan for traffic surges (static fallback page)

How Monitoring Helps

What Happens

A deployment introduces a bug that crashes the application, causes memory leaks, breaks critical functionality, or creates an infinite loop. This is the #1 cause of outages at most software companies.

Real-World Example

How to Prevent It

• Automated testing (unit, integration, end-to-end)
• Staged deployments (canary, blue-green)
• Quick rollback mechanisms
• Code review for all production changes

How Monitoring Helps

What Happens

DNS (Domain Name System) translates your domain name to an IP address. If DNS fails, browsers can't find your server at all. DNS issues include misconfigured records, propagation delays after changes, and DNS provider outages.

Real-World Example

How to Prevent It

• Use a reliable DNS provider (or two — secondary DNS)
• Don't make DNS changes on Friday afternoons
• Use low TTL values before planned changes
• Keep DNS records documented

How Monitoring Helps

What Happens

Your SSL/TLS certificate expires, and browsers display a frightening "Your connection is not private" warning. Most users leave immediately. Even with auto-renewal (Let's Encrypt), certificates can fail to renew due to DNS issues, server configuration changes, or permission problems.

Real-World Example

How to Prevent It

• Monitor certificate expiry dates
• Test auto-renewal actually works (not just that it's configured)
• Use monitoring that checks SSL validity, not just HTTP status

How Monitoring Helps

What Happens

Distributed Denial of Service attacks flood your server with traffic from thousands of sources, overwhelming its capacity. Attacks are increasingly common and can target any site, not just big companies.

Real-World Example

How to Prevent It

• Use a DDoS protection service (Cloudflare, AWS Shield)
• Rate limiting on your API and critical endpoints
• Have a response plan documented
• Keep your hosting provider's emergency contacts handy

How Monitoring Helps

What Happens

Your site depends on external services: payment processors, CDNs, analytics, authentication providers, APIs. When they go down, parts of your site break — sometimes silently.

Real-World Example

How to Prevent It

• Identify all third-party dependencies
• Implement graceful degradation (site works in reduced mode)
• Monitor critical third-party endpoints independently
• Have fallback options for essential services

How Monitoring Helps

What Happens

Database overload, disk space exhaustion, corrupted tables, slow queries, or connection pool saturation. The application can't read or write data, causing errors or extreme slowness.

Real-World Example

How to Prevent It

• Monitor database performance (query time, connections, disk space)
• Set up slow query alerts
• Regular database maintenance (indexing, vacuuming)
• Separate read/write replicas for heavy workloads

How Monitoring Helps

What Happens

Someone misconfigures a server, pushes to production instead of staging, deletes the wrong database, changes a firewall rule, or accidentally drops a table. This is arguably the #1 root cause across all incident categories.

Real-World Example

How to Prevent It

• Require confirmation for destructive operations
• Use infrastructure as code (reversible, reviewable)
• Separate production credentials from staging
• Limit production access to essential personnel

How Monitoring Helps

What Happens

Network connectivity problems between your server and your users. This can be ISP issues, peering problems, CDN node failures, or routing errors. Often regional — your site works in some countries but not others.

Real-World Example

How to Prevent It

• Use a CDN with multiple edge locations
• Monitor from multiple geographic regions
• Have a CDN bypass option for emergencies

How Monitoring Helps

What Happens

Your hosting provider (AWS, DigitalOcean, Hetzner, etc.) has an outage. This is rare for major providers but not impossible — even AWS has had significant multi-hour outages affecting millions of sites.

Real-World Example

How to Prevent It

• Multi-region or multi-cloud deployment for critical apps
• At minimum, be aware of your provider's status page
• Have a disaster recovery plan
• Consider a standby in a different provider

How Monitoring Helps

What Happens

Your domain registration expires. Your entire site disappears. Browsers can't even find it. This is rare but devastating — and recovery can take days if someone else registers your expired domain.

Real-World Example

How to Prevent It

• Enable auto-renewal with an up-to-date payment method
• Register domains for multiple years
• Set calendar reminders for renewal dates
• Monitor domain expiry dates

How Monitoring Helps