---
title: Error 503
description: Troubleshoot HTTP 503 error responses.
image: https://developers.cloudflare.com/core-services-preview.png
---

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# Error 503

## Error 503: service temporarily unavailable

HTTP error 503 occurs when your origin web server is overloaded.

### Common causes

There are different causes identifiable by the error message or the location of the error:

* Error does not contain `cloudflare` or `cloudflare-nginx` in the HTML response body. In this case, the issue is likely from your origin server.
* Error contains `cloudflare` or `cloudflare-nginx` in the HTML response body. In this case, the issue may stem from Cloudflare.
* Error is only visible in logs or analytics.

### Resolution

To resolve a `503` error, first determine whether the issue originates from your origin web server or Cloudflare. The following sections provide guidance on troubleshooting both scenarios.

#### 503 Error without `cloudflare` or `cloudflare-nginx`

If the error does not contain `cloudflare` or `cloudflare-nginx` in the HTML response body, contact your hosting provider to verify if they rate limit requests to your origin web server.

#### 503 Error with `cloudflare` or `cloudflare-nginx`

If the error contains `cloudflare` or `cloudflare-nginx` in the HTML response body, a connectivity issue occurred in a Cloudflare data center. Provide [Cloudflare support](https://developers.cloudflare.com/support/contacting-cloudflare-support/) with the following information:

* Your domain name
* The time and timezone of the `503` error occurrence
* The output of `www.example.com/cdn-cgi/trace` from the browser where the `503` error was observed (replace `www.example.com` with your actual domain and hostname)

#### 503 Error only visible in logs and analytics

These errors result from [unsuccessful prefetches from Speed Brain](https://developers.cloudflare.com/speed/optimization/content/speed-brain/#how-speed-brain-works) and can be discarded. These errors are not visible to visitors of your website. [Speed Brain](https://developers.cloudflare.com/speed/optimization/content/speed-brain/#enable-and-disable-speed-brain) can be disabled for the zone if needed (this feature cannot be disabled for a specific path).

### Workers-specific causes

Error 503 can also occur when using Cloudflare Workers:

* A Worker exceeds CPU time limits (see [Error 1102](https://developers.cloudflare.com/support/troubleshooting/http-status-codes/cloudflare-1xxx-errors/error-1102/))
* Worker code encounters memory limit issues (see [Error 1102](https://developers.cloudflare.com/support/troubleshooting/http-status-codes/cloudflare-1xxx-errors/error-1102/))

If you are using Workers, check the Workers dashboard for error logs and resource limit issues.

## Identifying the source of a 503 error

Use the error page content to determine whether a 503 was generated by Cloudflare or your origin server:

| Signal                                                          | Interpretation                                                                                                                     |
| --------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------- |
| Error page HTML contains cloudflare or cloudflare-nginx         | Generated by Cloudflare — refer to [503 Error with cloudflare or cloudflare-nginx](#503-error-with-cloudflare-or-cloudflare-nginx) |
| Error page HTML does not contain cloudflare or cloudflare-nginx | Your origin generated the 503 directly                                                                                             |

### Cloudflare-generated 503

A Cloudflare-generated 503 indicates a connectivity issue in a Cloudflare data center. Refer to [503 Error with cloudflare or cloudflare-nginx](#503-error-with-cloudflare-or-cloudflare-nginx) for next steps, and check **Security** \> **Events** for active mitigation events.

### Origin-generated 503

If your origin generated a 503, check origin server logs for signs of overload: CPU/memory saturation, exhausted connection pool, or application-level maintenance mode.

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