503 Service Unavailable
The website is up but refusing work for now: it's overloaded, in maintenance, or has no healthy backend servers. Try again later.
Quick checks
- Wait a few minutes and reload.
- Check the site's status page for maintenance.
- If it's a big launch or sale, traffic is probably the cause.
If you’re visiting the site
Wait and retry
- Reload after a few minutes; avoid rapid repeated reloads, which add load.
- If the page shows a time to come back, that's the Retry-After hint.
If you run the site
Find out who sends the 503
- The app, the web server, a load balancer (no healthy targets) or a CDN can all return 503. The response headers (Server, Via) usually tell you which.
Check capacity and health checks
- A load balancer returns 503 when every backend fails its health check. Check the health-check path and the instances.
- Raise worker counts or scale out if traffic exceeds capacity.
Use 503 correctly for maintenance
- Send
503with aRetry-Afterheader during planned maintenance, so search engines don't treat the outage as permanent.
- Send
Still not working?
If a 503 lasts more than a few hours, the service may be having a larger outage; check its status page.
See what’s happening
LightAtom's connections view shows when an app on your Mac keeps reconnecting to a service that's unavailable.
Frequently asked questions
Is 503 Service Unavailable temporary?
It's meant to be. Servers send it during overload or maintenance, often with a Retry-After header. A 503 that lasts days usually means a broken deployment.
Does a 503 hurt SEO?
Short outages with a 503 don't: search engines retry later. Weeks of 503 can lead to pages dropping from results.
What is the difference between 502 and 503?
502 means a gateway got a bad response from the backend. 503 means the server, or the load balancer, says it can't take requests right now.
Why do I get 503 from a load balancer?
No backend is healthy: all instances failed their health checks or none are registered. Check the targets and the health-check URL.