hx-indicator

The hx-indicator attribute allows you to specify the element that will have the htmx-request class added to it for the duration of the request. This can be used to show spinners or progress indicators while the request is in flight.

The value of this attribute is a CSS query selector of the element or elements to apply the class to.

Here is an example with a spinner adjacent to the button:

<div>
    <button hx-post="/example" hx-indicator="#spinner">
        Post It!
    </button>
    <img  id="spinner" class="htmx-indicator" src="/img/bars.svg"/>
</div>

When a request is in flight, this will cause the htmx-request class to be added to the #spinner image. The image also has the htmx-indicator class on it, which defines an opacity transition that will show the spinner:

    .htmx-indicator{
        opacity:0;
        transition: opacity 500ms ease-in;
    }
    .htmx-request .htmx-indicator{
        opacity:1
    }
    .htmx-request.htmx-indicator{
        opacity:1
    }

If you would prefer a different effect for showing the spinner you could define and use your own indicator CSS. Here is an example that uses display rather than opacity:

    .htmx-indicator{
        display:none;
    }
    .htmx-request .my-indicator{
        display:inline;
    }
    .htmx-request.my-indicator{
        display:inline;
    }

Note that the target of the hx-indicator selector need not be the exact element that you want to show: it can be any element in the parent hierarchy of the indicator.

Finally, note that the htmx-request class by default is added to the element causing the request, so you can place an indicator inside of that element and not need to explictly call it out with the hx-indicator attribute:

<button hx-post="/example">
    Post It!
   <img  class="htmx-indicator" src="/img/bars.svg"/>
</button>

Demo

This simulates what a spinner might look like in that situation:

Notes