HubSpot uses automatic image compression to reduce the size of your images and optimize the load speed of your content. If an image has a width attribute set in its markup, HubSpot adds a query string to the image src attribute to load a compressed version of the image. For example, if the following HTML was created in the editor:
<img src="my_image.jpg" width=420>
The COS will render the following markup with a timestamp and width query string, on the final page:
This feature allows users to upload larger image files and scale them down in the editor without having to worry about affecting the page's load speed. You can learn more about disabling automatic image compression here.