503 Service Unavailable

Updated 11 October 2026

Short answer

A 503 means the server is reachable but is refusing to handle requests right now. That's usually for one of three reasons: it's overloaded, it's deliberately in maintenance mode, or the app behind it has no capacity left (all workers busy, or out of memory or database connections). If traffic just spiked, it's overload. If someone was updating the site, check it isn't stuck in maintenance mode.

What's the problem

The site shows "503 Service Unavailable", "Service Temporarily Unavailable", or a maintenance message. It may come and go, often at busy times.

Why it happens

  • Too much traffic for the server: a sale, a newsletter, a mention somewhere popular, or bots.
  • Maintenance mode left on. WordPress, for example, puts up a maintenance page during updates and can get stuck if an update fails.
  • Resource limits reached: CPU, memory, worker processes or database connections. Cheap hosting plans hit these quickly.
  • The app is restarting or deploying and isn't ready yet.
  • Your hosting provider has throttled or suspended the account for using too many resources.

How to fix it

  1. Check if traffic spiked. Look at your analytics or hosting dashboard for the time it started.
  2. Check for maintenance mode. On WordPress, delete the .maintenance file in the site's root folder if an update was interrupted.
  3. Check server resources in your hosting dashboard: CPU, memory and process limits.
  4. Restart the app or web server to clear stuck workers.
  5. Look for bots. A large share of traffic from a few IP addresses or one country often means scraping or an attack. A firewall or rate limit helps.
  6. If it's regular overload, upgrade the plan, add caching so fewer requests reach the server, or move heavy work off the request path.

What Preventionlabs checks

One click runs the full report on your domain. For this problem it shows whether your site loads, how fast, and where its redirects go; up to 50 pages from your sitemap, listing any that fail or are slow, plus broken links on them. With Cloudflare connected, it also shows which pages returned server errors (5xx) to visitors, and when; which requests the firewall blocked, by Cloudflare's own rule names; recent deploys and account changes, with their times.

Run your free report

Your first report is free, no card needed. Then A$50 a month, up to 10 domains. Read-only: it never changes anything.

Sources

  1. MDN Web Docs: 503 Service UnavailablereferenceThe HTTP 503 Service Unavailable server error response status code indicates that the server is not ready to handle the request.
  2. MDN Web Docs: 503 Service UnavailablereferenceIn overload cases, some server-side applications will reject requests with a 503 status when resource thresholds like memory, CPU, or connection pool limits are met.
  3. WordPress: Common WordPress errorsofficial docsDelete the .maintenance file, which will be found in your site root.

Related

Server overloaded More work than the server can handle: a traffic spike, bots, a runaway process, or a slow query. Find what's using the CPU before upgrading. 429 Too Many Requests A rate limit was hit: too many requests too fast. On your site, check rate-limit and bot rules. In your app, slow down calls to that API. 502 Bad Gateway The server in front of your app got a bad answer, or none, from your app. Usually the app has crashed, isn't running, or is listening on the wrong port. Why is my website down? Check whether it's down for everyone, read the error on the page, then work through domain, hosting and recent changes. Most outages trace back to one of those.
← All of Error codes