htmx is designed to allow you to use CSS transitions to add smooth animations and transitions to your web page using only CSS and HTML. Below are a few examples of various animation techniques.
htmx also allows you to use the new View Transitions API for creating animations.
The simplest animation technique in htmx is to keep the id of an element stable across a content swap. If the
id of an element is kept stable, htmx will swap it in such a way that CSS transitions can be written between
the old version of the element and the new one.
Consider this div:
<style>
.smooth {
transition: all 1s ease-in;
}
</style>
<div id="color-demo" class="smooth" style="color:red"
hx-get="/colors" hx-swap="outerHTML" hx-trigger="every 1s">
Color Swap Demo
</div>
This div will poll every second and will get replaced with new content which changes the color style to a new value
(e.g. blue):
<div id="color-demo" class="smooth" style="color:blue"
hx-get="/colors" hx-swap="outerHTML" hx-trigger="every 1s">
Color Swap Demo
</div>
Because the div has a stable id, color-demo, htmx will structure the swap such that a CSS transition, defined on the
.smooth class, applies to the style update from red to blue, and smoothly transitions between them.
The Progress Bar demo uses this basic CSS animation technique as well, by updating the length
property of a progress bar element, allowing for a smooth animation.
If you want to fade out an element that is going to be removed when the request ends, you want to take advantage
of the htmx-swapping class with some CSS and extend the swap phase to be long enough for your animation to
complete. This can be done like so:
<style>
.fade-me-out.htmx-swapping {
opacity: 0;
transition: opacity 1s ease-out;
}
</style>
<button class="fade-me-out"
hx-delete="/fade_out_demo"
hx-swap="outerHTML swap:1s">
Fade Me Out
</button>
Building on the last example, we can fade in the new content by using the htmx-added class during the settle
phase. You can also write CSS transitions against the target, rather than the new content, by using the htmx-settling
class.
<style>
#fade-me-in.htmx-added {
opacity: 0;
}
#fade-me-in {
opacity: 1;
transition: opacity 1s ease-out;
}
</style>
<button id="fade-me-in"
hx-post="/fade_in_demo"
hx-swap="outerHTML settle:1s">
Fade Me In
</button>
You can also take advantage of the htmx-request class, which is applied to the element that triggers a request. Below
is a form that on submit will change its look to indicate that a request is being processed:
<style>
form.htmx-request {
opacity: .5;
transition: opacity 300ms linear;
}
</style>
<form hx-post="/name" hx-swap="outerHTML">
<label>Name:</label><input name="name"><br/>
<button>Submit</button>
</form>
class-tools ExtensionMany interesting animations can be created by using the class-tools extension.
Here is an example that toggles the opacity of a div. Note that we set the toggle time to be a bit longer than the transition time. This avoids flickering that can happen if the transition is interrupted by a class change.
<style>
.demo.faded {
opacity:.3;
}
.demo {
opacity:1;
transition: opacity ease-in 900ms;
}
</style>
<div class="demo" classes="toggle faded:1s">Toggle Demo</div>
htmx provides access to the new View Transitions API
via the transition option of the hx-swap attribute.
Below is an example of a swap that uses a view transition. The transition is tied to the outer div via a
view-transition-name property in CSS, and that transition is defined in terms of ::view-transition-old
and ::view-transition-new, using @keyframes to define the animation. (Fuller details on the View Transition
API can be found on the Chrome Developer Page on them.)
The old content of this transition should slide out to the left and the new content should slide in from the right.
Note that, as of this writing, the visual transition will only occur on Chrome 111+, but more browsers are expected to implement this feature in the near future.
<style>
@keyframes fade-in {
from { opacity: 0; }
}
@keyframes fade-out {
to { opacity: 0; }
}
@keyframes slide-from-right {
from { transform: translateX(90px); }
}
@keyframes slide-to-left {
to { transform: translateX(-90px); }
}
.slide-it {
view-transition-name: slide-it;
}
::view-transition-old(slide-it) {
animation: 180ms cubic-bezier(0.4, 0, 1, 1) both fade-out,
600ms cubic-bezier(0.4, 0, 0.2, 1) both slide-to-left;
}
::view-transition-new(slide-it) {
animation: 420ms cubic-bezier(0, 0, 0.2, 1) 90ms both fade-in,
600ms cubic-bezier(0.4, 0, 0.2, 1) both slide-from-right;
}
</style>
<div class="slide-it">
<h1>Initial Content</h1>
<button hx-get="/new-content" hx-swap="innerHTML transition:true" hx-target="closest div">
Swap It!
</button>
</div>
You can use the techniques above to create quite a few interesting and pleasing effects with plain old HTML while using htmx.