diff --git a/lib/Tinify.php b/lib/Tinify.php
index e2a970f..6cc7422 100644
--- a/lib/Tinify.php
+++ b/lib/Tinify.php
@@ -5,11 +5,18 @@
 const VERSION = "1.6.2";
 
 class Tinify {
+    const AUTHENTICATED = true;
+    const ANONYMOUS = false;
+
     private static $key = NULL;
     private static $appIdentifier = NULL;
     private static $proxy = NULL;
 
     private static $compressionCount = NULL;
+    private static $remainingCredits = NULL;
+    private static $payingState = NULL;
+    private static $emailAddress = NULL;
+
     private static $client = NULL;
 
     public static function setKey($key) {
@@ -17,6 +24,16 @@ public static function setKey($key) {
         self::$client = NULL;
     }
 
+    public static function getKey() {
+        return self::$key;
+    }
+
+    public static function createKey($email, $options) {
+        $body = array_merge(array("email" => $email), $options);
+        $response = self::getClient(self::ANONYMOUS)->request("post", "/keys", $body);
+        self::setKey($response->body->key);
+    }
+
     public static function setAppIdentifier($appIdentifier) {
         self::$appIdentifier = $appIdentifier;
         self::$client = NULL;
@@ -35,8 +52,32 @@ public static function setCompressionCount($compressionCount) {
         self::$compressionCount = $compressionCount;
     }
 
-    public static function getClient() {
-        if (!self::$key) {
+    public static function getRemainingCredits() {
+        return self::$remainingCredits;
+    }
+
+    public static function setRemainingCredits($remainingCredits) {
+        self::$remainingCredits = $remainingCredits;
+    }
+
+    public static function getPayingState() {
+        return self::$payingState;
+    }
+
+    public static function setPayingState($payingState) {
+        self::$payingState = $payingState;
+    }
+
+    public static function getEmailAddress() {
+        return self::$emailAddress;
+    }
+
+    public static function setEmailAddress($emailAddress) {
+        self::$emailAddress = $emailAddress;
+    }
+
+    public static function getClient($mode = self::AUTHENTICATED) {
+        if ($mode == self::AUTHENTICATED && !self::$key) {
             throw new AccountException("Provide an API key with Tinify\setKey(...)");
         }
 
@@ -56,6 +97,14 @@ function setKey($key) {
     return Tinify::setKey($key);
 }
 
+function getKey() {
+    return Tinify::getKey();
+}
+
+function createKey($email, $options) {
+    return Tinify::createKey($email, $options);
+}
+
 function setAppIdentifier($appIdentifier) {
     return Tinify::setAppIdentifier($appIdentifier);
 }
@@ -72,6 +121,18 @@ function compressionCount() {
     return Tinify::getCompressionCount();
 }
 
+function remainingCredits() {
+    return Tinify::getRemainingCredits();
+}
+
+function payingState() {
+    return Tinify::getPayingState();
+}
+
+function emailAddress() {
+    return Tinify::getEmailAddress();
+}
+
 function fromFile($path) {
     return Source::fromFile($path);
 }
@@ -86,7 +147,8 @@ function fromUrl($string) {
 
 function validate() {
     try {
-        Tinify::getClient()->request("post", "/shrink");
+        Tinify::getClient()->request("get", "/keys/" . Tinify::getKey());
+        return true;
     } catch (AccountException $err) {
         if ($err->status == 429) return true;
         throw $err;
diff --git a/lib/Tinify/Client.php b/lib/Tinify/Client.php
index 4dc820c..7c2bc03 100644
--- a/lib/Tinify/Client.php
+++ b/lib/Tinify/Client.php
@@ -8,7 +8,7 @@ class Client {
     const RETRY_COUNT = 1;
     const RETRY_DELAY = 500;
 
-    private $options;
+    protected $options;
 
     public static function userAgent() {
         $curl = curl_version();
@@ -19,7 +19,7 @@ private static function caBundle() {
         return __DIR__ . "/../data/cacert.pem";
     }
 
-    function __construct($key, $app_identifier = NULL, $proxy = NULL) {
+    function __construct($key, $appIdentifier = NULL, $proxy = NULL) {
         $curl = curl_version();
 
         if (!($curl["features"] & CURL_VERSION_SSL)) {
@@ -31,13 +31,15 @@ function __construct($key, $app_identifier = NULL, $proxy = NULL) {
             throw new ClientException("Your curl version {$version} is outdated; please upgrade to 7.18.1 or higher");
         }
 
+        $userAgent = join(" ", array_filter(array(self::userAgent(), $appIdentifier)));
+
         $this->options = array(
             CURLOPT_RETURNTRANSFER => true,
             CURLOPT_HEADER => true,
-            CURLOPT_USERPWD => "api:" . $key,
+            CURLOPT_USERPWD => $key ? ("api:" . $key) : NULL,
             CURLOPT_CAINFO => self::caBundle(),
             CURLOPT_SSL_VERIFYPEER => true,
-            CURLOPT_USERAGENT => join(" ", array_filter(array(self::userAgent(), $app_identifier))),
+            CURLOPT_USERAGENT => $userAgent,
         );
 
         if ($proxy) {
@@ -111,12 +113,16 @@ function request($method, $url, $body = NULL) {
                 $headers = self::parseHeaders(substr($response, 0, $headerSize));
                 $responseBody = substr($response, $headerSize);
 
-                if (isset($headers["compression-count"])) {
+                if ( isset($headers["compression-count"] ) ) {
                     Tinify::setCompressionCount(intval($headers["compression-count"]));
                 }
 
-                if ($status >= 200 && $status <= 299) {
-                    return (object) array("body" => $responseBody, "headers" => $headers);
+                if ( isset( $headers["compression-count-remaining"] ) ) {
+                    Tinify::setRemainingCredits( intval( $headers["compression-count-remaining"] ) );
+                }
+
+                if ( isset( $headers["paying-state"] ) ) {
+                    Tinify::setPayingState( $headers["paying-state"] );
                 }
 
                 $details = json_decode($responseBody);
@@ -130,8 +136,45 @@ function request($method, $url, $body = NULL) {
                     );
                 }
 
-                if ($retries > 0 && $status >= 500) continue;
-                throw Exception::create($details->message, $details->error, $status);
+                if ( isset( $headers["email-address"] ) ) {
+                    Tinify::setEmailAddress( $headers["email-address"] );
+                }
+
+                $isJson = false;
+                if (isset($headers["content-type"])) {
+                    /* Parse JSON response bodies. */
+                    list($contentType) = explode(";", $headers["content-type"], 2);
+                    if (strtolower(trim($contentType)) == "application/json") {
+                        $isJson = true;
+                    }
+                }
+
+                /* 1xx and 3xx are unexpected and will be treated as error. */
+                $isError = $status <= 199 || $status >= 300;
+
+                if ($isJson || $isError) {
+                    /* Parse JSON bodies, always interpret errors as JSON. */
+                    $responseBody = json_decode($responseBody);
+                    if (!$responseBody) {
+                        $message = sprintf("Error while parsing response: %s (#%d)",
+                            PHP_VERSION_ID >= 50500 ? json_last_error_msg() : "Error",
+                            json_last_error());
+                        if ($retries > 0 && $status >= 500) continue;
+                        throw Exception::create($message, "ParseError", $status);
+                    }
+                }
+
+                if ($isError) {
+                    if ($retries > 0 && $status >= 500) continue;
+                    /* When the key doesn't exist a 404 response is given. */
+                    if ($status == 404) {
+                        throw Exception::create(null, null, $status);
+                    } else {
+                        throw Exception::create($responseBody->message, $responseBody->error, $status);
+                    }
+                }
+
+                return (object) array("body" => $responseBody, "headers" => $headers);
             } else {
                 $message = sprintf("%s (#%d)", curl_error($request), curl_errno($request));
                 curl_close($request);
@@ -146,14 +189,14 @@ protected static function parseHeaders($headers) {
             $headers = explode("\r\n", $headers);
         }
 
-        $res = array();
+        $result = array();
         foreach ($headers as $header) {
             if (empty($header)) continue;
             $split = explode(":", $header, 2);
             if (count($split) === 2) {
-                $res[strtolower($split[0])] = trim($split[1]);
+                $result[strtolower($split[0])] = trim($split[1]);
             }
         }
-        return $res;
+        return $result;
     }
 }
diff --git a/lib/Tinify/Exception.php b/lib/Tinify/Exception.php
index d88bdef..2eb2a8c 100644
--- a/lib/Tinify/Exception.php
+++ b/lib/Tinify/Exception.php
@@ -6,7 +6,7 @@ class Exception extends \Exception {
     public $status;
 
     public static function create($message, $type, $status) {
-        if ($status == 401 || $status == 429) {
+        if ($status == 401 || $status == 403 || $status == 404 || $status == 429) {
             $klass = "Tinify\AccountException";
         } else if($status >= 400 && $status <= 499) {
             $klass = "Tinify\ClientException";
diff --git a/test/TinifyClientTest.php b/test/TinifyClientTest.php
index 8cb6761..a09e8b7 100644
--- a/test/TinifyClientTest.php
+++ b/test/TinifyClientTest.php
@@ -55,6 +55,36 @@ public function testRequestWhenValidShouldUpdateCompressionCount() {
         $this->assertSame(12, Tinify\getCompressionCount());
     }
 
+    public function testRequestWhenValidShouldUpdateRemainingCredits() {
+        CurlMock::register("https://api.tinify.com/", array(
+            "status" => 200, "headers" => array("Compression-Count-Remaining" => "488")
+        ));
+        $client = new Tinify\Client("key");
+        $client->request("get", "/");
+
+        $this->assertSame(488, Tinify\remainingCredits());
+    }
+
+    public function testRequestWhenValidShouldUpdatePayingState() {
+        CurlMock::register("https://api.tinify.com/", array(
+            "status" => 200, "headers" => array("Paying-State" => "free")
+        ));
+        $client = new Tinify\Client("key");
+        $client->request("get", "/");
+
+        $this->assertSame("free", Tinify\payingState());
+    }
+
+    public function testRequestWhenValidShouldUpdateEmailAddress() {
+        CurlMock::register("https://api.tinify.com/", array(
+            "status" => 200, "headers" => array("Email-Address" => "test@example.com")
+        ));
+        $client = new Tinify\Client("key");
+        $client->request("get", "/");
+
+        $this->assertSame("test@example.com", Tinify\emailAddress());
+    }
+
     public function testRequestWhenValidWithAppIdShouldIssueRequestWithUserAgent() {
         CurlMock::register("https://api.tinify.com/", array("status" => 200));
         $client = new Tinify\Client("key", "TestApp/0.1");
@@ -63,6 +93,29 @@ public function testRequestWhenValidWithAppIdShouldIssueRequestWithUserAgent() {
         $this->assertSame(Tinify\Client::userAgent() . " TestApp/0.1", CurlMock::last(CURLOPT_USERAGENT));
     }
 
+    public function testRequestWhenValidShouldParseJSONBody() {
+        CurlMock::register("https://api.tinify.com/", array(
+            "status" => 200,
+            "body" => '{"hello":"world"}',
+            "headers" => array("Content-Type" => "application/JSON; charset=utf-8")
+        ));
+        $client = new Tinify\Client("key");
+        $response = $client->request("post", "/");
+        $this->assertSame("world", $response->body->hello);
+    }
+
+    public function testRequestWhenValidShouldNotParseBinaryBody() {
+        CurlMock::register("https://api.tinify.com/", array(
+            "status" => 200,
+            "body" => "binary body",
+            "headers" => array("Content-Type" => "image/png")
+        ));
+        $client = new Tinify\Client("key");
+        $response = $client->request("post", "/");
+
+        $this->assertSame("binary body", $response->body);
+    }
+
     public function testRequestWhenValidWithProxyShouldIssueRequestWithProxyAuthorization() {
         CurlMock::register("https://api.tinify.com/", array("status" => 200));
         $client = new Tinify\Client("key", NULL, "http://user:pass@localhost:8080");
@@ -73,6 +126,23 @@ public function testRequestWhenValidWithProxyShouldIssueRequestWithProxyAuthoriz
         $this->assertSame("user:pass", CurlMock::last(CURLOPT_PROXYUSERPWD));
     }
 
+    public function testRequestWithBadJSONBodyThrowExceptionWithMessage() {
+        CurlMock::register("https://api.tinify.com/", array(
+            "status" => 200,
+            "body" => '<!-- this is not json -->',
+            "headers" => array("Content-Type" => "application/JSON"),
+        ));
+        if (PHP_VERSION_ID >= 50500) {
+            $this->setExpectedExceptionRegExp("Tinify\Exception",
+                "/Error while parsing response: Syntax error \(#4\) \(HTTP 200\/ParseError\)/");
+        } else {
+            $this->setExpectedExceptionRegExp("Tinify\Exception",
+                "/Error while parsing response: Error \(#4\) \(HTTP 200\/ParseError\)/");
+        }
+        $client = new Tinify\Client("key");
+        $client->request("get", "/");
+    }
+
     public function testRequestWithUnexpectedErrorOnceShouldReturnResponse() {
         CurlMock::register("https://api.tinify.com/", array(
             "error" => "Failed!", "errno" => 2
diff --git a/test/TinifyExceptionTest.php b/test/TinifyExceptionTest.php
new file mode 100644
index 0000000..2329e72
--- /dev/null
+++ b/test/TinifyExceptionTest.php
@@ -0,0 +1,13 @@
+<?php
+
+class TinifyExceptionTest extends TestCase {
+    public function testStatusShouldReturnStatusIfSet() {
+        $err = new Tinify\Exception("Message", "Error", 401);
+        $this->assertSame(401, $err->status);
+    }
+
+    public function testStatusShouldReturnNullIfUnset() {
+        $err = new Tinify\Exception("Message", "Error");
+        $this->assertSame(null, $err->status);
+    }
+}
diff --git a/test/TinifyTest.php b/test/TinifyTest.php
index e999668..39348da 100644
--- a/test/TinifyTest.php
+++ b/test/TinifyTest.php
@@ -3,6 +3,45 @@
 use Tinify\CurlMock;
 
 class ClientTest extends TestCase {
+    public function testGetKeyWithoutKeyShouldReturnNull() {
+        $this->assertSame(NULL, Tinify\getKey());
+    }
+
+    public function testGetKeyWithKeyShouldReturnKey() {
+        Tinify\setKey("abcde");
+        $this->assertSame("abcde", Tinify\getKey());
+    }
+
+    public function testCreateKeyWithNewEmailShouldSetKey() {
+        CurlMock::register("https://api.tinify.com/keys", array(
+            "status" => 202,
+            "body" => '{"key":"abcdefg123"}',
+            "headers" => array("Content-Type" => "application/json"),
+        ));
+
+        Tinify\createKey("user@example.com", array(
+            "name" => "John",
+            "identifier" => "My Tinify plugin",
+            "link" => "https://mywebsite.example.com/admin/settings",
+        ));
+
+        $this->assertSame("abcdefg123", Tinify\getKey());
+    }
+
+    public function testCreateKeyWithDuplicateEmailShouldThrowClientException() {
+        CurlMock::register("https://api.tinify.com/keys", array(
+            "status" => 403,
+            "body" => '{"error":"Duplicate registration","message":"This email address has already been used"}',
+        ));
+
+        $this->setExpectedException("Tinify\AccountException");
+        Tinify\createKey("user@example.com", array(
+            "name" => "John",
+            "identifier" => "My Tinify plugin",
+            "link" => "https://mywebsite.example.com/admin/settings",
+        ));
+    }
+
     public function testKeyShouldResetClientWithNewKey() {
         CurlMock::register("https://api.tinify.com/", array("status" => 200));
         Tinify\setKey("abcde");
@@ -63,24 +102,24 @@ public function testSetClientShouldReplaceClient() {
 
     public function testValidateWithValidKeyShouldReturnTrue() {
         Tinify\setKey("valid");
-        CurlMock::register("https://api.tinify.com/shrink", array(
-            "status" => 400, "body" => '{"error":"Input missing","message":"No input"}'
+        CurlMock::register("https://api.tinify.com/keys/valid", array(
+            "status" => 200, "body" => '{}'
         ));
         $this->assertTrue(Tinify\validate());
     }
 
     public function testValidateWithLimitedKeyShouldReturnTrue() {
-        Tinify\setKey("invalid");
-        CurlMock::register("https://api.tinify.com/shrink", array(
-            "status" => 429, "body" => '{"error":"Too many requests","message":"Your monthly limit has been exceeded"}'
+        Tinify\setKey("limited");
+        CurlMock::register("https://api.tinify.com/keys/limited", array(
+            "status" => 200, "body" => '{}'
         ));
         $this->assertTrue(Tinify\validate());
     }
 
     public function testValidateWithErrorShouldThrowException() {
         Tinify\setKey("invalid");
-        CurlMock::register("https://api.tinify.com/shrink", array(
-            "status" => 401, "body" => '{"error":"Unauthorized","message":"Credentials are invalid"}'
+        CurlMock::register("https://api.tinify.com/keys/invalid", array(
+            "status" => 404, "body" => '{}'
         ));
         $this->setExpectedException("Tinify\AccountException");
         Tinify\validate();