Website shows 503 Service Unavailable

Symptom#

Every page of a website returns HTTP Error 503. The service is unavailable, or a short "Service unavailable" page, while other sites on the server work. A 503 from IIS means the request reached the server, but no worker process could take it: in almost every case the site's application pool is stopped.

Cause 1: the subscription is suspended#

The service plan's Hosting Parameters tab has Websites of suspended subscriptions. With the default, Suspended, a suspended subscription keeps its site bindings, but its application pool is stopped so that visitors get HTTP 503 and no website code runs. A subscription is suspended when you or a reseller suspend the account, when it expires, or when its plan's Overuse policy suspends it after a limit is exceeded.

Check: open the subscription under Hosting Services › Subscriptions and look at its status. The customer's or reseller's account status is applied to all its subscriptions too.

Fix: activate it with Set Status (or Activate on the account), after sorting out the reason: renew the expiration, raise the limit or clean up disk space.

Cause 2: the application pool was stopped#

Go to Tools & Settings › IIS Application Pools and search for the website. If the pool's State is stopped while the subscription is active, click Start. Someone may have clicked Stop, or IIS stopped it, which is the next cause.

Cause 3: IIS disabled the pool after repeated crashes#

IIS rapid-fail protection stops an application pool whose worker process crashes several times in a short period. The site then answers 503 until the pool is started again, and it will stop again if the crash continues. Look in the Windows System event log for WAS warnings about the pool, for example with:

Get-WinEvent -LogName System -MaxEvents 50 | Where-Object ProviderName -eq 'Microsoft-Windows-WAS' | Format-List TimeCreated, Message

Typical reasons:

• The pool cannot start as its user. If the subscription's system user password no longer matches the pool's stored identity, WAS reports an invalid identity. Open the subscription and click Re-apply hosting settings on the Hosting card, or Re-apply settings on the website page, which writes the site and pool settings to IIS again.
• The application crashes on start. A broken web.config, a missing ASP.NET Core Hosting Bundle version or a .NET Framework version the application needs. Check the website's Logs, turn on Failed Request Tracing, and confirm the needed runtime under Tools & Settings › ASP.NET Settings.
• The memory limit. If the subscription's Memory limit is too low for the application, its processes get out-of-memory errors and can crash. Open the subscription's Resource Usage page and look at the Limit reached count and the memory graph. Raise the limit in the plan or for the subscription. PHP sites usually show HTTP 500 rather than 503 when they hit the limit.

After fixing the cause, start the pool again under IIS Application Pools and reload the site.

Cause 4: the server is short of memory#

When the server's commit limit is reached, new worker processes cannot start, and several sites may show 503 at once, often with "The paging file is too small" in the event log. The installer raises a fixed page file that is smaller than the RAM, but it takes effect only after a restart. Check memory on Home and in Server Management › Monitoring, restart the server if the installer changed the page file and you have not restarted since, and look for subscriptions without limits that use too much.

Still 503?#

Run Tools & Settings › Diagnose & Repair › Check Everything and repair the IIS findings. stackregent website-apply example.com on the server applies one website's settings again and prints the task log, which often names the problem. The websites chapter and the resource limits chapter have more detail.