diff --git a/app/Providers/TwigProvider.php b/app/Providers/TwigProvider.php
index 45177eb..1137d68 100644
--- a/app/Providers/TwigProvider.php
+++ b/app/Providers/TwigProvider.php
@@ -21,6 +21,7 @@ class TwigProvider
         ViewFunctions\Markdown::class,
         ViewFunctions\ParentDir::class,
         ViewFunctions\SizeForHumans::class,
+        ViewFunctions\Url::class,
     ];
 
     /** @var Container The application container */
diff --git a/app/ViewFunctions/Url.php b/app/ViewFunctions/Url.php
new file mode 100644
index 0000000..41586ff
--- /dev/null
+++ b/app/ViewFunctions/Url.php
@@ -0,0 +1,23 @@
+<?php
+
+namespace App\ViewFunctions;
+
+class Url extends ViewFunction
+{
+    /** @var string The function name */
+    protected $name = 'url';
+
+    /**
+     * Return the URL for a given path.
+     *
+     * @param string $path
+     *
+     * @return string
+     */
+    public function __invoke(string $path): string
+    {
+        $url = dirname($_SERVER['SCRIPT_NAME']) . '/' . ltrim($path, '/');
+
+        return '/' . trim($url, '/');
+    }
+}
diff --git a/app/resources/views/components/header.twig b/app/resources/views/components/header.twig
index 6bc764d..74c182c 100644
--- a/app/resources/views/components/header.twig
+++ b/app/resources/views/components/header.twig
@@ -1,7 +1,7 @@
 <header id="header" class="bg-blue-600 shadow sticky top-0">
     <div class="container flex flex-col justify-between items-center mx-auto p-4 md:flex-row">
         <div class="font-mono text-white text-sm tracking-tight mb-2 md:my-1">
-            <a href="/" class="hover:underline">Home</a>
+            <a href="{{ url('/') }}" class="hover:underline">Home</a>
 
             {% if path %}
                 {% for name, path in breadcrumbs(path) %}
diff --git a/tests/ViewFunctions/UrlTest.php b/tests/ViewFunctions/UrlTest.php
new file mode 100644
index 0000000..dd166ad
--- /dev/null
+++ b/tests/ViewFunctions/UrlTest.php
@@ -0,0 +1,29 @@
+<?php
+
+namespace Tests\ViewFunctions;
+
+use App\ViewFunctions\Url;
+use Tests\TestCase;
+
+class UrlTest extends TestCase
+{
+    public function test_it_can_return_a_url(): void
+    {
+        $url = new Url($this->container, $this->config);
+
+        $this->assertEquals('/', $url('/'));
+        $this->assertEquals('/some/path', $url('some/path'));
+        $this->assertEquals('/some/file.test', $url('some/file.test'));
+    }
+
+    public function test_it_can_return_a_url_in_a_subdirectory(): void
+    {
+        $_SERVER['SCRIPT_NAME'] = '/some/dir/index.php';
+
+        $url = new Url($this->container, $this->config);
+
+        $this->assertEquals('/some/dir', $url('/'));
+        $this->assertEquals('/some/dir/some/path', $url('some/path'));
+        $this->assertEquals('/some/dir/some/file.test', $url('some/file.test'));
+    }
+}