How can I force a web server to reload changed images in a different subdirectory?

I have a slideshow with the HTML for it on one page, but the images are stored in a different subdirectory on the server. When I change the images, the server does not detect the change (at least not for a long time) and the old images continue to display. I know how to force a server to refresh a page, but these images are not part of an HTML page. I have no control over how the server operates–I’m just creating the website.

My guess is that there is not a way for the HTML page to do the updates. If that is correct then suggestions for a solution likely require additional information. Such as:

  • How are the images uploaded?
  • How does the HTML use the images?
  • If you are able to update the page to get the new images used then how do you do that?

I do not know if all or any of those questions are relevant but that is at least the type of additional information that will help.

To force a web server to reload changed images in a different subdirectory, you typically have a few options:

  1. Clear Browser Cache: The simplest method is to clear your browser cache. When you reload the page, the browser will fetch the updated images from the server.

  2. Change File Names: If you’re frequently updating images, you can append a version number or timestamp to the image file names. For example, image.jpg can become image_v2.jpg or image_20240506.jpg. This forces the browser to see it as a new image and fetch it from the server.

  3. Query String: You can add a query string to the image URL with a unique parameter each time the image changes. For instance, image.jpg?v=1, image.jpg?v=2, and so on. This signals to the browser that the resource is different from what it has cached.

  4. HTTP Cache Headers: Configure your web server to send appropriate cache-control headers. You can set the Cache-Control header to no-cache or max-age=0 for the directory containing the images. This tells the browser to revalidate the cache before using the cached version.

  5. Server-Side Scripting: If you have server-side scripting capabilities (like PHP, Node.js, etc.), you can dynamically generate the image URLs with unique identifiers each time the page is loaded.

Here’s a simple example using PHP:

<img src="path/to/images/image.jpg?<?php echo time(); ?>" alt="Image">

In this example, time() function generates a unique timestamp each time the page loads, forcing the browser to fetch a new version of the image.

Choose the method that best fits your requirements and technical capabilities.

Thank you for that full and very helpful reply. Appending a version number is the option available to me (I use it when I change my basic scripts.js file because the server takes a long time to “realize” there has been a change). I don’t have any control of or access to the server (aside from uploading files to it); otherwise option #4 sounds ideal because it would include all the many places where there is a link to a resource that is in a different directory.