---
title: Website Downtime: the most common causes (and how to prevent each)
description: Most outages aren't mysterious — they come from the same short list of causes, again and again. Here's that list, what each one looks like, and how to stop it taking your site down.
canonical: https://watchfor.io/blog/website-downtime-causes
---

# Website Downtime: the most common causes (and how to prevent each)

2026-05-23 · WatchFor Team · Monitoring · uptime, reliability, incidents

Most outages aren't mysterious — they come from the same short list of causes, again and again. Here's that list, what each one looks like, and how to stop it taking your site down.

When a site goes down, it feels like a unique catastrophe. It almost never is. Pull back and look across thousands of outages and the same handful of causes show up over and over — which is great news, because a known list of causes is a list you can defend against.

Here's the usual suspects, what each looks like in the wild, and the concrete way to stop it.

## The usual suspects

| Cause | What it looks like | How to prevent it |
| --- | --- | --- |
| **Expired SSL certificate** | Full-screen browser security warning; total block | Auto-renew **and** independently monitor expiry |
| **Expired domain** | Site (and email) vanish overnight | Auto-renew the domain; monitor its expiry date |
| **DNS misconfiguration** | "Server not found"; the server is fine, nobody can reach it | Monitor DNS resolution and expected records |
| **Server / app errors (5xx)** | 500s and 502s; deploys gone wrong | Health checks, staged rollouts, fast rollback |
| **Traffic spikes** | Slow then unreachable under load | Autoscaling, caching, a CDN, load testing |
| **Slow / failing database** | Timeouts, 504s, half-loading pages | Monitor query latency; connection limits; failover |
| **Third-party dependency** | A payment or API provider fails, taking you with it | Timeouts, circuit breakers, graceful degradation |
| **Human error / bad deploy** | "It was fine five minutes ago" | Code review, staging, feature flags, easy rollback |

If you've ever had an outage, it was almost certainly on this list. Let's look at the big ones.

## The avoidable classics

### Expired certificates and domains

These deserve a special mention because they're **100% preventable and 100% embarrassing**. A lapsed certificate or domain takes everything down — site *and* email — usually on a weekend. Auto-renewal helps, but it fails silently more often than you'd think. The fix is a second, independent layer: a monitor that watches the actual expiry date and warns you weeks ahead. (We wrote a whole guide on [never getting caught by an expired SSL certificate](/blog/ssl-certificate-expiry).)

### DNS problems

When [DNS breaks](/blog/how-dns-works), your server is perfectly healthy — visitors just can't find it. A typo'd record, a deleted entry, or a change that hasn't finished caching can all take you offline while every server-side dashboard stays green. The only way to catch it is to monitor DNS *itself*.

### Bad deploys and server errors

The most common self-inflicted outage: a deploy ships a bug, and suddenly everything returns [500s or 502s](/blog/http-status-codes-explained). The defenses are well known — review, staging, **staged (canary) rollouts**, and above all a **fast, reliable rollback** so a bad release is a five-minute blip, not an hour-long incident.

### Traffic spikes

Your big moment — a launch, a feature on the news — becomes your worst moment as load overwhelms the servers. Caching, a CDN, and autoscaling absorb the surge; load testing beforehand tells you where you'll break *before* your customers find out.

### Third-party dependencies

You're only as reliable as the services you call. A payment gateway, an auth provider, or an external API can drag you down with it. Defend with **timeouts** (don't wait forever), **circuit breakers** (stop hammering a dead dependency), and **graceful degradation** (lose a feature, not the whole site).

## The one thing that ties it all together

Notice a pattern in that table? Nearly every cause is something you can **detect early** — *if* something is watching for it. The difference between a minor blip and a major incident is almost always **how fast you found out**.

> **You can't prevent every outage — but you can make sure you're never the last to know.** Prevention reduces how often things break; monitoring reduces how long they stay broken.

Good monitoring covers the whole list: uptime and error checks for server problems, [certificate](/docs/monitors/certificates) and domain expiry, [DNS](/docs/monitors/network) resolution, response-time checks for overload and slow databases — all confirmed from [multiple locations](/docs/reference/probe-locations) and alerting the right people the moment something slips.

## The bottom line

| Takeaway | In one line |
| --- | --- |
| Outages aren't mysterious | They come from the same short list. |
| The classics are preventable | Certs, domains and DNS should never surprise you. |
| Deploys cause many outages | Stage, flag, and make rollback instant. |
| Speed beats perfection | You can't prevent everything — but you can find out first. |

Downtime is part of running anything online. But most of it is predictable, and almost all of it is *catchable*. Defend against the common causes, watch for the rest, and you turn "the site is down and I have no idea why" into "we caught it in three minutes and it's already fixed."

Start with [Uptime Monitoring 101](/blog/uptime-monitoring-101), or set up your first checks with the [monitors guide](/docs/monitors).

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Canonical page: https://watchfor.io/blog/website-downtime-causes · All articles: https://watchfor.io/blog/all.md · Site guide: https://watchfor.io/llms.txt