htmx 4.0 is under construction — migration guide

hx-boost

Convert links and forms to AJAX

The hx-boost attribute allows you to “boost” normal anchors and form tags to use AJAX instead. This has the nice fallback that, if the user does not have javascript enabled, the site will continue to work.

Syntax

<div hx-boost="true">
  <a href="/page1">Go To Page 1</a>
</div>

For anchor tags, clicking on the anchor will issue a GET request to the url specified in the href and will push the url so that a history entry is created. The target is the <body> tag, and the innerHTML swap strategy is used by default. All of these can be modified by using the appropriate attributes, except the click trigger.

For forms the request will be converted into a GET or POST, based on the method in the method attribute and will be triggered by a submit. Again, the target will be the body of the page, and the innerHTML swap will be used. The url will not be pushed, however, and no history entry will be created. (You can use the hx-push-url attribute if you want the url to be pushed.)

Here is an example of some boosted links:

<div hx-boost="true">
  <a href="/page1">Go To Page 1</a>
  <a href="/page2">Go To Page 2</a>
</div>

These links will issue an ajax GET request to the respective URLs and replace the body’s inner content with it.

Here is an example of a boosted form:

<form hx-boost="true" action="/example" method="post">
    <input name="email" type="email" placeholder="Enter email...">
    <button>Submit</button>
</form>

This form will issue an ajax POST to the given URL and replace the body’s inner content with it.

Advanced Syntax

You can configure boost behavior using a config string that sets swap, target, and other options directly on the hx-boost attribute. Use hx-boost:inherited to pass that config down to all boosted descendants:

<body hx-boost:inherited='swap:"innerHTML", target:"#main", select:"#content"'>
  <div id="main">
    <!-- Boosted links inherit the config -->
    <a href="/page1">Go To Page 1</a>
    <a href="/page2">Go To Page 2</a>

    <!-- Override with a different boost config -->
    <div hx-boost:inherited='swap:"outerHTML", target:"#result"'>
      <a href="/page3">Page 3 (uses div config)</a>

      <!-- Disable boost for a specific link -->
      <a href="/external" hx-boost="false">External</a>

      <!-- Custom boost config on the element itself overrides all -->
      <a href="/page4" hx-boost='swap:"beforeend", target:"#list"'>Page 4</a>
    </div>

    <!-- Non-boosted elements are unaffected -->
    <div hx-get="/data" hx-trigger="load">Loading...</div>
  </div>
</body>

The key advantage is that boost config only applies to boosted elements (links and forms), unlike inherited hx-* attributes which would affect all descendant htmx elements.

Priority Order

Boost config overrides explicit hx-* attributes on the element:

  1. Boost config (highest priority)
  2. Explicit hx-* attributes
  3. Default values (lowest priority)

This allows you to:

  • Set base defaults with hx-target, hx-swap on elements
  • Override them with hx-boost:inherited at any level
  • Use hx-boost="true" or hx-boost="false" to enable/disable

Supported modifiers:

  • swap:STYLE - Swap strategy (innerHTML, outerHTML, etc.)
  • target:SELECTOR - Target element selector
  • select:SELECTOR - Content selection from response

Notes

  • Only links that are to the same domain and that are not local anchors will be boosted
  • All requests are done via AJAX, so keep that in mind when doing things like redirects
  • To find out if the request results from a boosted anchor or form, look for HX-Boosted in the request header
  • Selectively disable boost on child elements with hx-boost="false"
  • Disable the replacement of elements via boost, and their children, with hx-preserve="true"