Why Do Websites Go Down? 8 Common Causes Explained
Traffic spikes, DNS failures, expired certificates, bad deploys — the eight real reasons sites go offline, explained without jargon.
“The website is down” sounds like one problem, but it's eight different ones wearing a trench coat. Understanding the real causes helps you diagnose faster — and appreciate why even giants like Google and Meta go dark sometimes.
1. Traffic spikes and overload
The classic: more visitors than the servers can handle. Product launches, viral moments, and ticket sales regularly melt unprepared infrastructure. Servers queue requests until they start timing out — that's your 503 errors.
2. DNS failures
DNS is the internet's phone book. If a site's DNS records break or its DNS provider has an outage, the domain simply stops resolving — the servers are fine, but nobody can find them. Huge outages have been caused by nothing but DNS.
3. Expired SSL certificates
HTTPS certificates expire — usually yearly. Forget to renew and browsers start showing terrifying security warnings or refusing to connect at all. It's embarrassingly common, even at large companies. (You can check any site's certificate with our SSL expiry checker.)
4. Bad deployments
A new code release with a bug can take down a site in seconds — a bad database migration, a broken config file, a typo in infrastructure code. The faster a company ships, the more this happens; good ones roll back in minutes.
5. DDoS attacks
Distributed denial-of-service: floods of junk traffic from compromised devices, designed to drown a site. Mitigation exists (that's much of what Cloudflare sells), but big attacks still knock sites offline.
6. Hosting and cloud provider outages
Most websites rent infrastructure. When AWS, Cloudflare, or another giant has a bad day, thousands of sites go down together — which is why unrelated sites often break simultaneously.
7. Database failures
The web server is up but the database behind it choked — corrupted data, a failed failover, or simply a query load the database can't survive. Symptoms: the homepage loads, but anything requiring login or dynamic content fails.
8. Human error and config changes
The single biggest cause, insiders say. A wrong command, a firewall rule that blocks legitimate traffic, a BGP route withdrawn by accident — the October 2021 Facebook blackout was ultimately a configuration change gone wrong.
The pattern
Notice what's not on the list: hackers in hoodies “hacking the mainframe.” Real outages are overwhelmingly mundane — expired certificates, bad configs, too much traffic. When your favorite site dies, it's usually someone's very bad day at work, fixed within hours.
Don't guess — test it. Our free checker tells you in seconds whether any website is up or down.
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