--- description: Troubleshoot HTTP 503 error responses. title: Error 503 image: https://developers.cloudflare.com/og-docs.png --- [Skip to content](#main-content) > Documentation Index > Fetch the complete documentation index at: https://developers.cloudflare.com/support/llms.txt > Use this file to discover all available pages before exploring further. # Error 503 Last updated Aug 24, 2026|Copy as Markdown|[View as Markdown](https://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/support/troubleshooting/http-status-codes/cloudflare-5xx-errors/error-503/index.md)|[Agent setup](https://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/agent-setup/) ## 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://docs-durable-objects-instance-replaced-errors.previews.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://docs-durable-objects-instance-replaced-errors.previews.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://docs-durable-objects-instance-replaced-errors.previews.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://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/support/troubleshooting/http-status-codes/cloudflare-1xxx-errors/error-1102/)) * Worker code encounters memory limit issues (see [Error 1102](https://docs-durable-objects-instance-replaced-errors.previews.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. Was this helpful? YesNo ## On this page [![](https://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/_astro/logo.te5VL_aD.svg)Docs](https://docs-durable-objects-instance-replaced-errors.previews.developers.cloudflare.com/) ```json {"@context":"https://schema.org","@type":"TechArticle","@id":"https://developers.cloudflare.com/support/troubleshooting/http-status-codes/cloudflare-5xx-errors/error-503/#page","headline":"Error 503 · Cloudflare Support docs","description":"Troubleshoot HTTP 503 error responses.","url":"https://developers.cloudflare.com/support/troubleshooting/http-status-codes/cloudflare-5xx-errors/error-503/","inLanguage":"en","image":"https://developers.cloudflare.com/og-docs.png","dateModified":"2026-08-24","publisher":{"@type":"Organization","name":"Cloudflare","description":"One platform for your apps, agents, and workforce. Build, secure, and scale without managing infrastructure","url":"https://www.cloudflare.com/","sameAs":["https://github.com/cloudflare","https://www.linkedin.com/company/cloudflare","https://x.com/cloudflare"],"logo":{"@type":"ImageObject","url":"https://developers.cloudflare.com/logo.svg"},"address":{"@type":"PostalAddress","streetAddress":"101 Townsend St","addressLocality":"San Francisco","addressRegion":"CA","postalCode":"94107","addressCountry":"US"},"contactPoint":[{"@type":"ContactPoint","contactType":"Customer Support","url":"https://support.cloudflare.com/","availableLanguage":["English"]},{"@type":"ContactPoint","contactType":"Sales","url":"https://www.cloudflare.com/contact/","availableLanguage":["English"]}]},"isPartOf":{"@type":"WebSite","@id":"https://developers.cloudflare.com/#website","name":"Cloudflare Docs","url":"https://developers.cloudflare.com/"}} ```