diff --git a/src/Command/InstallCommand.php b/src/Command/InstallCommand.php
index aefd24d..5006be5 100644
--- a/src/Command/InstallCommand.php
+++ b/src/Command/InstallCommand.php
@@ -8,6 +8,8 @@
 use Php\Pie\DependencyResolver\DependencyResolver;
 use Php\Pie\Downloading\DownloadAndExtract;
 use Php\Pie\Installing\Install;
+use Php\Pie\Installing\InstallNotification\FailedToSendInstallNotification;
+use Php\Pie\Installing\InstallNotification\InstallNotification;
 use Php\Pie\Platform\TargetPlatform;
 use Symfony\Component\Console\Attribute\AsCommand;
 use Symfony\Component\Console\Command\Command;
@@ -25,6 +27,7 @@ public function __construct(
         private readonly DownloadAndExtract $downloadAndExtract,
         private readonly Build $build,
         private readonly Install $install,
+        private readonly InstallNotification $installNotification,
     ) {
         parent::__construct();
     }
@@ -62,6 +65,17 @@ public function execute(InputInterface $input, OutputInterface $output): int
 
         ($this->install)($downloadedPackage, $targetPlatform, $output);
 
+        try {
+            $this->installNotification->send($targetPlatform, $downloadedPackage);
+        } catch (FailedToSendInstallNotification $failedToSendInstallNotification) {
+            if ($output->isVeryVerbose()) {
+                $output->writeln('Install notification did not send.');
+                if ($output->isDebug()) {
+                    $output->writeln($failedToSendInstallNotification->__toString());
+                }
+            }
+        }
+
         return Command::SUCCESS;
     }
 }
diff --git a/src/Container.php b/src/Container.php
index 56f9a59..f865420 100644
--- a/src/Container.php
+++ b/src/Container.php
@@ -31,6 +31,8 @@
 use Php\Pie\Downloading\UnixDownloadAndExtract;
 use Php\Pie\Downloading\WindowsDownloadAndExtract;
 use Php\Pie\Installing\Install;
+use Php\Pie\Installing\InstallNotification\InstallNotification;
+use Php\Pie\Installing\InstallNotification\SendInstallNotificationUsingGuzzle;
 use Php\Pie\Installing\UnixInstall;
 use Php\Pie\Installing\WindowsInstall;
 use Php\Pie\Platform\TargetPhp\ResolveTargetPhpToPlatformRepository;
@@ -138,6 +140,8 @@ static function (ContainerInterface $container): Install {
             },
         );
 
+        $container->alias(SendInstallNotificationUsingGuzzle::class, InstallNotification::class);
+
         return $container;
     }
 }
diff --git a/src/DependencyResolver/Package.php b/src/DependencyResolver/Package.php
index 3fab599..30d203b 100644
--- a/src/DependencyResolver/Package.php
+++ b/src/DependencyResolver/Package.php
@@ -27,6 +27,8 @@ public function __construct(
         public readonly string $version,
         public readonly string|null $downloadUrl,
         public readonly array $configureOptions,
+        public readonly string|null $notificationUrl,
+        public readonly string $notificationVersion,
     ) {
     }
 
@@ -48,6 +50,8 @@ public static function fromComposerCompletePackage(CompletePackageInterface $com
             $completePackage->getPrettyVersion(),
             $completePackage->getDistUrl(),
             $configureOptions,
+            $completePackage->getNotificationUrl(),
+            $completePackage->getVersion(),
         );
     }
 
diff --git a/src/Installing/InstallNotification/FailedToSendInstallNotification.php b/src/Installing/InstallNotification/FailedToSendInstallNotification.php
new file mode 100644
index 0000000..2a2da13
--- /dev/null
+++ b/src/Installing/InstallNotification/FailedToSendInstallNotification.php
@@ -0,0 +1,32 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Php\Pie\Installing\InstallNotification;
+
+use Php\Pie\Downloading\DownloadedPackage;
+use Psr\Http\Message\RequestInterface;
+use Psr\Http\Message\ResponseInterface;
+use RuntimeException;
+
+use function sprintf;
+
+class FailedToSendInstallNotification extends RuntimeException
+{
+    public static function fromFailedResponse(
+        DownloadedPackage $package,
+        RequestInterface $request,
+        ResponseInterface $response,
+    ): self {
+        return new self(sprintf(
+            "Failed to notify package %s installation to %s [%d]:\n\n"
+            . "Request: %s\n\n"
+            . 'Response: %s',
+            $package->package->prettyNameAndVersion(),
+            $request->getUri(),
+            $response->getStatusCode(),
+            $request->getBody()->__toString(),
+            $response->getBody()->__toString(),
+        ));
+    }
+}
diff --git a/src/Installing/InstallNotification/InstallNotification.php b/src/Installing/InstallNotification/InstallNotification.php
new file mode 100644
index 0000000..718b176
--- /dev/null
+++ b/src/Installing/InstallNotification/InstallNotification.php
@@ -0,0 +1,23 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Php\Pie\Installing\InstallNotification;
+
+use Php\Pie\Downloading\DownloadedPackage;
+use Php\Pie\Platform\TargetPlatform;
+
+/**
+ * Send a notification to Packagist that the package was installed. This is
+ * used for package analytics (i.e. download counts)
+ *
+ * @internal This is not public API for PIE, so should not be depended upon unless you accept the risk of BC breaks
+ */
+interface InstallNotification
+{
+    /** @throws FailedToSendInstallNotification */
+    public function send(
+        TargetPlatform $targetPlatform,
+        DownloadedPackage $package,
+    ): void;
+}
diff --git a/src/Installing/InstallNotification/SendInstallNotificationUsingGuzzle.php b/src/Installing/InstallNotification/SendInstallNotificationUsingGuzzle.php
new file mode 100644
index 0000000..c176fa7
--- /dev/null
+++ b/src/Installing/InstallNotification/SendInstallNotificationUsingGuzzle.php
@@ -0,0 +1,94 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Php\Pie\Installing\InstallNotification;
+
+use Composer\Composer;
+use GuzzleHttp\ClientInterface;
+use GuzzleHttp\Psr7\Request;
+use GuzzleHttp\RequestOptions;
+use Php\Pie\Downloading\DownloadedPackage;
+use Php\Pie\Platform\TargetPlatform;
+
+use function array_key_exists;
+use function function_exists;
+use function is_array;
+use function json_decode;
+use function json_encode;
+use function php_uname;
+use function sprintf;
+
+/** @internal This is not public API for PIE, so should not be depended upon unless you accept the risk of BC breaks */
+final class SendInstallNotificationUsingGuzzle implements InstallNotification
+{
+    /** @psalm-suppress PossiblyUnusedMethod no direct reference; used in service locator */
+    public function __construct(private readonly ClientInterface $client)
+    {
+    }
+
+    public function send(
+        TargetPlatform $targetPlatform,
+        DownloadedPackage $package,
+    ): void {
+        if ($package->package->notificationUrl === null) {
+            return;
+        }
+
+        $notificationRequest = new Request(
+            'POST',
+            $package->package->notificationUrl,
+            [
+                'Content-Type' => 'application/json',
+                /**
+                 * User agent format is important! If it isn't right, Packagist
+                 * silently discards the payload.
+                 *
+                 * @link https://github.com/composer/packagist/blob/fb75c17d75bc032cc88b997275d40077511d0cd9/src/Controller/ApiController.php#L296
+                 * @link https://github.com/composer/packagist/blob/fb75c17d75bc032cc88b997275d40077511d0cd9/src/Util/UserAgentParser.php#L28-L38
+                 */
+                'User-Agent' => sprintf(
+                    'Composer/%s (%s; %s; %s; %s)',
+                    Composer::getVersion(),
+                    function_exists('php_uname') ? php_uname('s') : 'Unknown',
+                    function_exists('php_uname') ? php_uname('r') : 'Unknown',
+                    'PHP ' . $targetPlatform->phpBinaryPath->version(),
+                    'cURL ' . TargetPlatform::getCurlVersion(),
+                ),
+            ],
+            /**
+             * @link https://github.com/composer/packagist/blob/main/src/Controller/ApiController.php#L248
+             * @see \Composer\Installer\InstallationManager::notifyInstalls()
+             */
+            json_encode([
+                'downloads' => [
+                    [
+                        'name' => $package->package->name,
+                        'version' => $package->package->notificationVersion,
+                        'downloaded' => false,
+                    ],
+                ],
+            ]),
+        );
+
+        $notificationResponse = $this->client->send(
+            $notificationRequest,
+            [RequestOptions::HTTP_ERRORS => false],
+        );
+
+        /** @var mixed $responseBody */
+        $responseBody = json_decode($notificationResponse->getBody()->__toString(), true);
+
+        if (
+            ! is_array($responseBody)
+            || ! array_key_exists('status', $responseBody)
+            || $responseBody['status'] !== 'success'
+        ) {
+            throw FailedToSendInstallNotification::fromFailedResponse(
+                $package,
+                $notificationRequest,
+                $notificationResponse,
+            );
+        }
+    }
+}
diff --git a/src/Platform/TargetPlatform.php b/src/Platform/TargetPlatform.php
index 548aa08..ce7625e 100644
--- a/src/Platform/TargetPlatform.php
+++ b/src/Platform/TargetPlatform.php
@@ -7,8 +7,10 @@
 use Php\Pie\Platform\TargetPhp\PhpBinaryPath;
 
 use function array_key_exists;
+use function curl_version;
 use function explode;
 use function function_exists;
+use function is_string;
 use function posix_getuid;
 use function preg_match;
 use function trim;
@@ -29,6 +31,20 @@ public function __construct(
     ) {
     }
 
+    public static function getCurlVersion(): string
+    {
+        static $curlVersion = null;
+
+        if ($curlVersion === null) {
+            $curlVersionList = curl_version();
+            $curlVersion     = array_key_exists('version', $curlVersionList) && is_string($curlVersionList['version'])
+                ? $curlVersionList['version']
+                : null;
+        }
+
+        return (string) $curlVersion;
+    }
+
     public static function isRunningAsRoot(): bool
     {
         return function_exists('posix_getuid') && posix_getuid() === 0;
diff --git a/test/integration/Building/UnixBuildTest.php b/test/integration/Building/UnixBuildTest.php
index 2605e9f..08e6b58 100644
--- a/test/integration/Building/UnixBuildTest.php
+++ b/test/integration/Building/UnixBuildTest.php
@@ -39,6 +39,8 @@ public function testUnixBuildCanBuildExtension(): void
                 '0.1.0',
                 null,
                 [ConfigureOption::fromComposerJsonDefinition(['name' => 'enable-pie_test_ext'])],
+                null,
+                '0.1.0.0',
             ),
             self::TEST_EXTENSION_PATH,
         );
diff --git a/test/integration/Installing/UnixInstallTest.php b/test/integration/Installing/UnixInstallTest.php
index afd28e4..efd9eb3 100644
--- a/test/integration/Installing/UnixInstallTest.php
+++ b/test/integration/Installing/UnixInstallTest.php
@@ -46,6 +46,8 @@ public function testUnixInstallCanInstallExtension(): void
                 '0.1.0',
                 null,
                 [ConfigureOption::fromComposerJsonDefinition(['name' => 'enable-pie_test_ext'])],
+                null,
+                '0.1.0.0',
             ),
             self::TEST_EXTENSION_PATH,
         );
diff --git a/test/integration/Installing/WindowsInstallTest.php b/test/integration/Installing/WindowsInstallTest.php
index 011394a..9703a84 100644
--- a/test/integration/Installing/WindowsInstallTest.php
+++ b/test/integration/Installing/WindowsInstallTest.php
@@ -52,6 +52,8 @@ public function testWindowsInstallCanInstallExtension(): void
                 '1.2.3',
                 null,
                 [],
+                null,
+                '1.2.3.0',
             ),
             self::TEST_EXTENSION_PATH,
         );
diff --git a/test/unit/Command/CommandHelperTest.php b/test/unit/Command/CommandHelperTest.php
index bbdd5c0..bd49cbb 100644
--- a/test/unit/Command/CommandHelperTest.php
+++ b/test/unit/Command/CommandHelperTest.php
@@ -109,6 +109,8 @@ public function testDownloadPackage(): void
                 '1.2.3',
                 'https://test-uri/',
                 [],
+                null,
+                '1.2.3.0',
             ));
 
         $downloadAndExtract->expects(self::once())
@@ -155,6 +157,8 @@ public function testProcessingConfigureOptionsFromInput(): void
                 ]),
                 ConfigureOption::fromComposerJsonDefinition(['name' => 'enable-thing']),
             ],
+            null,
+            '1.0.0.0',
         );
         $inputDefinition = new InputDefinition();
         $inputDefinition->addOption(new InputOption('with-stuff', null, InputOption::VALUE_REQUIRED));
diff --git a/test/unit/Downloading/AddAuthenticationHeaderTest.php b/test/unit/Downloading/AddAuthenticationHeaderTest.php
index 03f3a5c..4ba1e22 100644
--- a/test/unit/Downloading/AddAuthenticationHeaderTest.php
+++ b/test/unit/Downloading/AddAuthenticationHeaderTest.php
@@ -40,6 +40,8 @@ public function testAuthorizationHeaderIsAdded(): void
                 '1.2.3',
                 $downloadUrl,
                 [],
+                null,
+                '1.2.3.0',
             ),
             $authHelper,
         );
@@ -63,6 +65,8 @@ public function testExceptionIsThrownWhenPackageDoesNotHaveDownloadUrl(): void
             '1.2.3',
             null,
             [],
+            null,
+            '1.2.3.0',
         );
 
         $this->expectException(RuntimeException::class);
diff --git a/test/unit/Downloading/DownloadedPackageTest.php b/test/unit/Downloading/DownloadedPackageTest.php
index 3419f4e..de2ade8 100644
--- a/test/unit/Downloading/DownloadedPackageTest.php
+++ b/test/unit/Downloading/DownloadedPackageTest.php
@@ -25,6 +25,8 @@ public function testFromPackageAndExtractedPath(): void
             '1.2.3',
             null,
             [],
+            null,
+            '1.2.3.0',
         );
 
         $extractedSourcePath = uniqid('/path/to/downloaded/package', true);
diff --git a/test/unit/Downloading/Exception/CouldNotFindReleaseAssetTest.php b/test/unit/Downloading/Exception/CouldNotFindReleaseAssetTest.php
index 7b1311b..ef8fe60 100644
--- a/test/unit/Downloading/Exception/CouldNotFindReleaseAssetTest.php
+++ b/test/unit/Downloading/Exception/CouldNotFindReleaseAssetTest.php
@@ -28,6 +28,8 @@ public function testForPackage(): void
             '1.2.3',
             null,
             [],
+            null,
+            '1.2.3.0',
         );
 
         $exception = CouldNotFindReleaseAsset::forPackage($package, ['something.zip', 'something2.zip']);
@@ -44,6 +46,8 @@ public function testForPackageWithMissingTag(): void
             '1.2.3',
             null,
             [],
+            null,
+            '1.2.3.0',
         );
 
         $exception = CouldNotFindReleaseAsset::forPackageWithMissingTag($package);
diff --git a/test/unit/Downloading/GithubPackageReleaseAssetsTest.php b/test/unit/Downloading/GithubPackageReleaseAssetsTest.php
index 21e3dc1..51b548d 100644
--- a/test/unit/Downloading/GithubPackageReleaseAssetsTest.php
+++ b/test/unit/Downloading/GithubPackageReleaseAssetsTest.php
@@ -74,6 +74,8 @@ public function testUrlIsReturnedWhenFindingWindowsDownloadUrl(): void
             '1.2.3',
             'https://test-uri/' . uniqid('downloadUrl', true),
             [],
+            null,
+            '1.2.3.0',
         );
 
         $releaseAssets = new GithubPackageReleaseAssets($authHelper, $guzzleMockClient, 'https://test-github-api-base-url.thephp.foundation');
@@ -126,6 +128,8 @@ public function testUrlIsReturnedWhenFindingWindowsDownloadUrlWithCompilerAndThr
             '1.2.3',
             'https://test-uri/' . uniqid('downloadUrl', true),
             [],
+            null,
+            '1.2.3.0',
         );
 
         $releaseAssets = new GithubPackageReleaseAssets($authHelper, $guzzleMockClient, 'https://test-github-api-base-url.thephp.foundation');
@@ -164,6 +168,8 @@ public function testFindWindowsDownloadUrlForPackageThrowsExceptionWhenAssetNotF
             '1.2.3',
             'https://test-uri/' . uniqid('downloadUrl', true),
             [],
+            null,
+            '1.2.3.0',
         );
 
         $releaseAssets = new GithubPackageReleaseAssets($authHelper, $guzzleMockClient, 'https://test-github-api-base-url.thephp.foundation');
diff --git a/test/unit/Downloading/UnixDownloadAndExtractTest.php b/test/unit/Downloading/UnixDownloadAndExtractTest.php
index e460e9c..d650f0a 100644
--- a/test/unit/Downloading/UnixDownloadAndExtractTest.php
+++ b/test/unit/Downloading/UnixDownloadAndExtractTest.php
@@ -67,6 +67,8 @@ public function testInvoke(): void
             '1.2.3',
             $downloadUrl,
             [],
+            null,
+            '1.2.3.0',
         );
 
         $downloadedPackage = $unixDownloadAndExtract->__invoke($targetPlatform, $requestedPackage);
diff --git a/test/unit/Downloading/WindowsDownloadAndExtractTest.php b/test/unit/Downloading/WindowsDownloadAndExtractTest.php
index 36e0cc5..d266fb9 100644
--- a/test/unit/Downloading/WindowsDownloadAndExtractTest.php
+++ b/test/unit/Downloading/WindowsDownloadAndExtractTest.php
@@ -82,6 +82,8 @@ public function testInvoke(): void
             '1.2.3',
             'https://test-uri/' . uniqid('downloadUrl', true),
             [],
+            null,
+            '1.2.3.0',
         );
 
         $downloadedPackage = $windowsDownloadAndExtract->__invoke($targetPlatform, $requestedPackage);
diff --git a/test/unit/Installing/InstallNotification/SendInstallNotificationUsingGuzzleTest.php b/test/unit/Installing/InstallNotification/SendInstallNotificationUsingGuzzleTest.php
new file mode 100644
index 0000000..97858ac
--- /dev/null
+++ b/test/unit/Installing/InstallNotification/SendInstallNotificationUsingGuzzleTest.php
@@ -0,0 +1,161 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Php\PieUnitTest\Installing\InstallNotification;
+
+use Composer\Composer;
+use GuzzleHttp\ClientInterface;
+use GuzzleHttp\Psr7\Response;
+use Php\Pie\DependencyResolver\Package;
+use Php\Pie\Downloading\DownloadedPackage;
+use Php\Pie\ExtensionName;
+use Php\Pie\ExtensionType;
+use Php\Pie\Installing\InstallNotification\FailedToSendInstallNotification;
+use Php\Pie\Installing\InstallNotification\SendInstallNotificationUsingGuzzle;
+use Php\Pie\Platform\Architecture;
+use Php\Pie\Platform\OperatingSystem;
+use Php\Pie\Platform\TargetPhp\PhpBinaryPath;
+use Php\Pie\Platform\TargetPlatform;
+use Php\Pie\Platform\ThreadSafetyMode;
+use Php\Pie\Platform\WindowsCompiler;
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\MockObject\MockObject;
+use PHPUnit\Framework\TestCase;
+use Psr\Http\Message\RequestInterface;
+
+use function function_exists;
+use function json_encode;
+use function php_uname;
+use function sprintf;
+
+#[CoversClass(SendInstallNotificationUsingGuzzle::class)]
+final class SendInstallNotificationUsingGuzzleTest extends TestCase
+{
+    private const FAKE_PHP_VERSION = '6.0.0';
+
+    private ClientInterface&MockObject $client;
+    private TargetPlatform $targetPlatform;
+
+    public function setUp(): void
+    {
+        parent::setUp();
+
+        $this->client = $this->createMock(ClientInterface::class);
+
+        $phpBinaryPath = $this->createMock(PhpBinaryPath::class);
+        $phpBinaryPath->expects(self::any())
+            ->method('version')
+            ->willReturn(self::FAKE_PHP_VERSION);
+
+        $this->targetPlatform = new TargetPlatform(
+            OperatingSystem::Windows,
+            $phpBinaryPath,
+            Architecture::x86,
+            ThreadSafetyMode::ThreadSafe,
+            WindowsCompiler::VC14,
+        );
+    }
+
+    private function downloadedPackageWithNotificationUrl(string|null $notificationUrl): DownloadedPackage
+    {
+        return DownloadedPackage::fromPackageAndExtractedPath(
+            new Package(
+                ExtensionType::PhpModule,
+                ExtensionName::normaliseFromString('foo'),
+                'bar/foo',
+                '1.2.3',
+                null,
+                [],
+                $notificationUrl,
+                '1.2.3.0',
+            ),
+            '/path/to/extracted',
+        );
+    }
+
+    public function testNullNotificationUrlDoesNoNotification(): void
+    {
+        $this->client->expects(self::never())
+            ->method('send');
+
+        $sender = new SendInstallNotificationUsingGuzzle($this->client);
+        $sender->send(
+            $this->targetPlatform,
+            $this->downloadedPackageWithNotificationUrl(null),
+        );
+    }
+
+    public function testSuccessfulPayload(): void
+    {
+        $this->client->expects(self::once())
+            ->method('send')
+            ->with(self::callback(static function (RequestInterface $request) {
+                self::assertSame('http://example.com/notification', $request->getUri()->__toString());
+                self::assertSame('POST', $request->getMethod());
+                self::assertSame('application/json', $request->getHeaderLine('Content-Type'));
+                self::assertSame(
+                    sprintf(
+                        'Composer/%s (%s; %s; %s; %s)',
+                        Composer::getVersion(),
+                        function_exists('php_uname') ? php_uname('s') : 'Unknown',
+                        function_exists('php_uname') ? php_uname('r') : 'Unknown',
+                        'PHP ' . self::FAKE_PHP_VERSION,
+                        'cURL ' . TargetPlatform::getCurlVersion(),
+                    ),
+                    $request->getHeaderLine('User-Agent'),
+                );
+
+                return true;
+            }))
+            ->willReturn(new Response(
+                201,
+                [],
+                json_encode(['status' => 'success']),
+            ));
+
+        $sender = new SendInstallNotificationUsingGuzzle($this->client);
+        $sender->send(
+            $this->targetPlatform,
+            $this->downloadedPackageWithNotificationUrl('http://example.com/notification'),
+        );
+    }
+
+    public function testPartialSuccessThrowsException(): void
+    {
+        $this->client->expects(self::once())
+            ->method('send')
+            ->with(self::callback(static function (RequestInterface $request) {
+                self::assertSame('http://example.com/notification', $request->getUri()->__toString());
+                self::assertSame('POST', $request->getMethod());
+                self::assertSame('application/json', $request->getHeaderLine('Content-Type'));
+                self::assertSame(
+                    sprintf(
+                        'Composer/%s (%s; %s; %s; %s)',
+                        Composer::getVersion(),
+                        function_exists('php_uname') ? php_uname('s') : 'Unknown',
+                        function_exists('php_uname') ? php_uname('r') : 'Unknown',
+                        'PHP ' . self::FAKE_PHP_VERSION,
+                        'cURL ' . TargetPlatform::getCurlVersion(),
+                    ),
+                    $request->getHeaderLine('User-Agent'),
+                );
+
+                return true;
+            }))
+            /** @link https://github.com/composer/packagist/blob/fb75c17d75bc032cc88b997275d40077511d0cd9/src/Controller/ApiController.php#L326 */
+            ->willReturn(new Response(
+                200,
+                [],
+                json_encode(['status' => 'partial', 'message' => 'Packages (blah) not found']),
+            ));
+
+        $sender = new SendInstallNotificationUsingGuzzle($this->client);
+
+        $this->expectException(FailedToSendInstallNotification::class);
+        $sender->send(
+            $this->targetPlatform,
+            $this->downloadedPackageWithNotificationUrl('http://example.com/notification'),
+        );
+    }
+}
diff --git a/test/unit/Platform/WindowsExtensionAssetNameTest.php b/test/unit/Platform/WindowsExtensionAssetNameTest.php
index 29025df..6bcc448 100644
--- a/test/unit/Platform/WindowsExtensionAssetNameTest.php
+++ b/test/unit/Platform/WindowsExtensionAssetNameTest.php
@@ -45,6 +45,8 @@ public function setUp(): void
             '1.2.3',
             null,
             [],
+            null,
+            '1.2.3.0',
         );
     }