`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, or the keyword closest, followed by a CSS selector, which will find the closest ancestor element or itself, that matches the given CSS selector (e.g. closest tr);

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 (Note that we use my-indicator instead of htmx-indicator):

    .my-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 explicitly 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

hx-indicator is inherited and can be placed on a parent element
In the absence of an explicit indicator, the htmx-request class will be added to the element triggering the request
If you want to use your own CSS but still use htmx-indicator as class name, then you need to disable includeIndicatorStyles. See Configuring htmx. The easiest way is to add this to the <head> of your HTML:

<meta name="htmx-config" content='{"includeIndicatorStyles": false}'>