Cache Warmup
Updated this week

The cache warmup system has two primary functions:

  1. Keeping the site optimized when automated cache purges happen

  2. Preemptively optimizing all pages found in a configured URL source.

The warmup system prepares optimized versions of your pages without having to wait for organic traffic. This is great because it helps you prepare your pages for visitors without relying on organic traffic.

For optimal results, the system needs a source of links for your site. You can choose the Standard method, which will use your homepage URL to identify popular pages or a sitemap XML.

Important: The option to provide a sitemap XML is available only for users on paid plans.

If a sitemap is configured, it will take precedence. Otherwise, only the links found on your homepage will be warmed up.

If you don’t define a source, the system will warm up only URLs purged via automated events (for example, after editing a post, changing the price of a product, etc.).

When the Standard mode is chosen, or a sitemap is configured, you should click on the "Update" button to start the warmup process.

Once you click the button, the system estimates how many optimizations will be used in the process. After the estimate is done, the warmup process will start automatically.

The warmup system prepares optimized versions for desktop and mobile devices.

Additionally, when Variation cookies with known values are configured, the system will prepare optimized versions of all possible combinations of the cookies and their known values. This ensures great coverage of possible organic requests resulting in a much better cache hit ratio after the warmup is complete.

Further information for this feature implementation per platform can be found in the following articles:

Possible errors

In case NitroPack faces an issue accessing your website or Sitemap URL, you will be notified of this in our Dashboard.

Below is a list of the possible errors that you may encounter. πŸ‘‡

Unexpected error

This error message can be seen for various reasons, and we suggest reaching out to our Support team to dig deeper by using the chat bubble in the bottom right corner of this page.

Invalid sitemap format

This usually indicates that you have added a non-XML sitemap in the Cache Warmup settings.

For NitroPack to be able to crawl a sitemap, it should be formatted as an XML file without any errors present.

Error 403 (NitroPack cannot access your sitemap)

This error message usually indicates that NitroPack has faced a 403 Forbidden error when trying to access your website's sitemap.

To resolve this, we recommend that you whitelist NitroPack's IP addresses:




You should also double-check your server settings and ensure that the file is publicly accessible.

Error 404 (Sitemap not found)

Essentially, NitroPack encountered a 404 Not Found error when accessing your website's sitemap.

This usually means that the file itself does not exist or is not publicly available.

To solve this, we recommend making sure that the file is publicly accessible or re-uploading your sitemap with the correct URL.

Sitemap Index Contains No URLs

This error occurs when the sitemap XML you provided does not contain any URLs. A sitemap is essential for the cache warmup process as it guides which pages should be pre-loaded. Ensure that your XML sitemap is correctly formatted and includes URLs that you want to be pre-loaded.

To resolve this:

  • Verify the structure and content of your XML file

  • Adjust the XML file to include valid URLs only

  • Once you fix your XML, go to Cache Warmup, click "Edit," and re-upload your sitemap XML to re-initiate the process

Optimize-only URLs Not in Sitemap

This error indicates a mismatch between the URLs designated for optimization-only in the Cache Settings and the URLs listed in your sitemap. This discrepancy can prevent proper cache warmup because the system cannot locate the optimize-only URLs in the sitemap.

How to fix this error:

  • Review the list of optimize-only URLs in the Cache Settings

  • Cross-check these URLs with those in your sitemap to ensure there are no discrepancies

  • Once you're done, go to Cache Warmup, click "Edit," and re-upload your sitemap XML to re-initiate the process

Excluded URLs Match All Sitemap URLs

This error message emerges when all URLs listed in your sitemap XML file are also listed in the Excluded URLs feature. This prevents any URLs from being pre-loaded during the cache warmup.

To solve this, review the list of Excluded URLs in the Cache Settings and remove any that do not need to be there.

Once you update the Exlcuded URLs list, re-upload your sitemap XML in Cache Warmup to re-initiate the optimization process.

πŸ“Œ If you need any assistance or have questions, you can always reach out to our support team at [email protected] or by using the chat bubble located in the bottom right corner of this page.

Did this answer your question?