diff --git a/src/ext/ajax-header.js b/src/ext/ajax-header.js
new file mode 100644
index 00000000..1891699d
--- /dev/null
+++ b/src/ext/ajax-header.js
@@ -0,0 +1,7 @@
+htmx.defineExtension('ajax-header', {
+ onEvent: function (name, evt) {
+ if (name === "configRequest.htmx") {
+ evt.detail.headers['X-Requested-With'] = 'XMLHttpRequest';
+ }
+ }
+});
\ No newline at end of file
diff --git a/test/ext/ajax-header.js b/test/ext/ajax-header.js
new file mode 100644
index 00000000..0888ef3b
--- /dev/null
+++ b/test/ext/ajax-header.js
@@ -0,0 +1,21 @@
+describe("ajax-header extension", function() {
+ beforeEach(function () {
+ this.server = makeServer();
+ clearWorkArea();
+ });
+ afterEach(function () {
+ this.server.restore();
+ clearWorkArea();
+ });
+
+ it('Sends the X-Requested-With header', function () {
+ this.server.respondWith("GET", "/test", function (xhr) {
+ xhr.respond(200, {}, xhr.requestHeaders['X-Requested-With'])
+ });
+ var btn = make('')
+ btn.click();
+ this.server.respond();
+ btn.innerHTML.should.equal("XMLHttpRequest");
+ });
+
+});
\ No newline at end of file
diff --git a/test/index.html b/test/index.html
index 1b47a4dd..358f207f 100644
--- a/test/index.html
+++ b/test/index.html
@@ -121,6 +121,8 @@
+
+
diff --git a/www/extensions.md b/www/extensions.md
index 1c8771ce..f3633ad0 100644
--- a/www/extensions.md
+++ b/www/extensions.md
@@ -54,6 +54,7 @@ against `htmx` in each distribution
| [`rails-method`](/extensions/rails-method) | includes the `_method` parameter in requests for rails compatibility
| [`remove-me`](/extensions/remove-me) | allows you to remove an element after a given amount of time
| [`include-vals`](/extensions/include-vals) | allows you to include additional values in a request
+| [`ajax-header`](/extensions/ajax-header) | includes the commonly-used X-Requested-With header that identifies ajax requests in many backend frameworks
diff --git a/www/extensions/ajax-header.md b/www/extensions/ajax-header.md
new file mode 100644
index 00000000..39566150
--- /dev/null
+++ b/www/extensions/ajax-header.md
@@ -0,0 +1,22 @@
+---
+layout: layout.njk
+title: htmx - high power tools for html
+---
+
+## The `ajax-header` Extension
+
+This extension adds the X-Requested-With header to requests with the value "XMLHttpRequest".
+
+This header is commonly used by javascript frameworks to differentiate ajax requests from normal http requests.
+
+### Usage
+
+```html
+
+ ...
+
+```
+
+### Source
+
+