This script allows you to check to see if a resource URL exists. It returns a value of "yes" or "no". A common use of this plugin would be to check if an external resource exists within a conditional to set up an alternative if the resource comes back with a 404.
Here’s an example of setting a variable using the plugin syntax:
{preload_replace:has_photo="{exp:easy_file_exists url='{photo}'}"}
Then, later in the template:
<img src="{if has_photo='yes'}{photo}{if:else}{default_avatar}{/if}" class="user-avatar" alt="" />
This is extremely useful when the file in question is an external resource as a simple {if photo} will evaluate as "true" if {photo} has a value, but the conditional does not check against the actual availability of the linked resource.