How can I look for changes in a large binary file on a site?

If you want to use Simon to detect when a large binary file like an app changes, one option would be to use a Web Page test with the download URL. But that would end up storing the entire download in the test, slowing it down and possibly causing loading or saving failures, as that large amount of data is encoded in JSON.

A better option is to just get a checksum of the file. That would only need to store a small amount of data, and would still result in a change when combined with a filter like Any Change.

Here’s a custom script-based service to assist with this; you can download it from the Simon Extras page:

Here’s a direct download of the script.

As always, you can add this a a new service in Simon via these easy steps:

Download and decompress the downloaded archive, if your browser didn’t do it for you.

Go to the Services list in Simon.

Click the New toolbar button (or via the File menu).

On the Name page, give the new service a suitable name, like “Checksum”.

Choose the Service Kind button to show the service page.

Choose the Script service kind, if not selected by default.

Click the Open Script… button and choose the script file.

Click Done to finish editing the new service.

You can then add a new test and choose this new service, entering a URL to check, and using the default Any Changes filter.

Enjoy!