diff --git a/fixtures/different_extension.inc b/fixtures/different_extension.inc
new file mode 100644
index 0000000..b3d9bbc
--- /dev/null
+++ b/fixtures/different_extension.inc
@@ -0,0 +1 @@
+<?php
diff --git a/src/Indexer.php b/src/Indexer.php
index 85d1787..a9e3335 100644
--- a/src/Indexer.php
+++ b/src/Indexer.php
@@ -53,6 +53,11 @@ class Indexer
      */
     private $documentLoader;
 
+    /**
+     * @var Options
+     */
+    private $options;
+
     /**
      * @var \stdClasss
      */
@@ -70,6 +75,7 @@ class Indexer
      * @param Cache             $cache
      * @param DependenciesIndex $dependenciesIndex
      * @param Index             $sourceIndex
+     * @param Options           $options
      * @param PhpDocumentLoader $documentLoader
      * @param \stdClass|null    $composerLock
      */
@@ -81,6 +87,7 @@ class Indexer
         DependenciesIndex $dependenciesIndex,
         Index $sourceIndex,
         PhpDocumentLoader $documentLoader,
+        Options $options,
         \stdClass $composerLock = null,
         \stdClass $composerJson = null
     ) {
@@ -91,6 +98,7 @@ class Indexer
         $this->dependenciesIndex = $dependenciesIndex;
         $this->sourceIndex = $sourceIndex;
         $this->documentLoader = $documentLoader;
+        $this->options = $options;
         $this->composerLock = $composerLock;
         $this->composerJson = $composerJson;
     }
@@ -103,8 +111,8 @@ class Indexer
     public function index(): Promise
     {
         return coroutine(function () {
-
-            $pattern = Path::makeAbsolute('**/*.php', $this->rootPath);
+            $fileTypes = implode(',', $this->options->fileTypes);
+            $pattern = Path::makeAbsolute('**/*{' . $fileTypes . '}', $this->rootPath);
             $uris = yield $this->filesFinder->find($pattern);
 
             $count = count($uris);
@@ -213,7 +221,7 @@ class Indexer
                 yield timeout();
                 $this->client->window->logMessage(MessageType::LOG, "Parsing $uri");
                 try {
-                    $document = yield $this->documentLoader->load($uri);
+                    $document = yield $this->documentLoader->load($uri, $this->options->fileSizeLimit);
                     if (!isVendored($document, $this->composerJson)) {
                         $this->client->textDocument->publishDiagnostics($uri, $document->getDiagnostics());
                     }
diff --git a/src/LanguageServer.php b/src/LanguageServer.php
index 46281f5..b29cb1d 100644
--- a/src/LanguageServer.php
+++ b/src/LanguageServer.php
@@ -163,11 +163,12 @@ class LanguageServer extends AdvancedJsonRpc\Dispatcher
      * @param ClientCapabilities $capabilities The capabilities provided by the client (editor)
      * @param string|null $rootPath The rootPath of the workspace. Is null if no folder is open.
      * @param int|null $processId The process Id of the parent process that started the server. Is null if the process has not been started by another process. If the parent process is not alive then the server should exit (see exit notification) its process.
+     * @param Options $initializationOptions The options send from client to initialize the server
      * @return Promise <InitializeResult>
      */
-    public function initialize(ClientCapabilities $capabilities, string $rootPath = null, int $processId = null): Promise
+    public function initialize(ClientCapabilities $capabilities, string $rootPath = null, int $processId = null, Options $initializationOptions = null): Promise
     {
-        return coroutine(function () use ($capabilities, $rootPath, $processId) {
+        return coroutine(function () use ($capabilities, $rootPath, $processId, $initializationOptions) {
 
             if ($capabilities->xfilesProvider) {
                 $this->filesFinder = new ClientFilesFinder($this->client);
@@ -186,6 +187,7 @@ class LanguageServer extends AdvancedJsonRpc\Dispatcher
             $this->projectIndex = new ProjectIndex($sourceIndex, $dependenciesIndex, $this->composerJson);
             $stubsIndex = StubsIndex::read();
             $this->globalIndex = new GlobalIndex($stubsIndex, $this->projectIndex);
+            $initializationOptions = $initializationOptions ?? new Options;
 
             // The DefinitionResolver should look in stubs, the project source and dependencies
             $this->definitionResolver = new DefinitionResolver($this->globalIndex);
@@ -230,8 +232,10 @@ class LanguageServer extends AdvancedJsonRpc\Dispatcher
                     $dependenciesIndex,
                     $sourceIndex,
                     $this->documentLoader,
+                    $initializationOptions,
                     $this->composerLock,
-                    $this->composerJson
+                    $this->composerJson,
+                    $initializationOptions
                 );
                 $indexer->index()->otherwise('\\LanguageServer\\crash');
             }
@@ -255,7 +259,9 @@ class LanguageServer extends AdvancedJsonRpc\Dispatcher
                     $sourceIndex,
                     $this->composerLock,
                     $this->documentLoader,
-                    $this->composerJson
+                    $this->composerJson,
+                    $indexer,
+                    $initializationOptions
                 );
             }
 
diff --git a/src/Options.php b/src/Options.php
new file mode 100644
index 0000000..81a0fa5
--- /dev/null
+++ b/src/Options.php
@@ -0,0 +1,89 @@
+<?php
+declare(strict_types = 1);
+
+namespace LanguageServer;
+
+class Options
+{
+    /**
+     * File types the indexer should process
+     *
+     * @var string[]
+     */
+    public $fileTypes = ['.php'];
+
+    /**
+     * Maximum file size to index
+     *
+     * @var int
+     */
+    public $fileSizeLimit = 150000;
+
+    /**
+     * Validate/Filter input and set options for file types
+     *
+     * @param string[] $fileTypes List of file types
+     */
+    public function setFileTypes(array $fileTypes)
+    {
+        $fileTypes = filter_var_array($fileTypes, FILTER_SANITIZE_STRING);
+        $fileTypes = filter_var($fileTypes, FILTER_CALLBACK, ['options' => [$this, 'filterFileTypes']]);
+        $fileTypes = array_filter($fileTypes, 'strlen');
+        $fileTypes = array_values($fileTypes);
+
+        $this->fileTypes = !empty($fileTypes) ? $fileTypes : $this->fileTypes;
+    }
+
+    /**
+     * Validate/Filter input and set option for file size limit
+     *
+     * @param string $fileSizeLimit Size in human readable format or -1 for unlimited
+     */
+    public function setFileSizeLimit(string $fileSizeLimit)
+    {
+        $fileSizeLimit = filter_var($fileSizeLimit, FILTER_SANITIZE_STRING);
+
+        if ($fileSizeLimit === '-1') {
+            $this->fileSizeLimit = PHP_INT_MAX;
+        } else {
+            $this->fileSizeLimit = $this->convertFileSize($fileSizeLimit);
+        }
+    }
+
+    /**
+     * Filter valid file type
+     *
+     * @param string $fileType The file type to filter
+     * @return string|bool If valid it returns the file type, otherwise false
+     */
+    private function filterFileTypes(string $fileType)
+    {
+        $fileType = trim($fileType);
+
+        if (empty($fileType)) {
+            return $fileType;
+        }
+
+        if (substr($fileType, 0, 1) !== '.') {
+            return false;
+        }
+
+        return $fileType;
+    }
+
+    /**
+     * Convert human readable file size to byte
+     *
+     * @param string $fileSize
+     * @return int
+     */
+    private function convertFileSize(string $fileSize)
+    {
+        preg_match('/(\d+)(\w)/', $fileSize, $match);
+        $sizes = 'KMG';
+        $size = (int) $match[1];
+        $factor = strpos($sizes, strtoupper($match[2])) + 1;
+
+        return $size * pow(1000, $factor);
+    }
+}
diff --git a/src/PhpDocumentLoader.php b/src/PhpDocumentLoader.php
index 57a7e9c..7bcb067 100644
--- a/src/PhpDocumentLoader.php
+++ b/src/PhpDocumentLoader.php
@@ -100,13 +100,12 @@ class PhpDocumentLoader
      * The document is NOT added to the list of open documents, but definitions are registered.
      *
      * @param string $uri
+     * @param int $limit
      * @return Promise <PhpDocument>
      */
-    public function load(string $uri): Promise
+    public function load(string $uri, int $limit): Promise
     {
-        return coroutine(function () use ($uri) {
-
-            $limit = 150000;
+        return coroutine(function () use ($uri, $limit) {
             $content = yield $this->contentRetriever->retrieve($uri);
             $size = strlen($content);
             if ($size > $limit) {
diff --git a/tests/LanguageServerTest.php b/tests/LanguageServerTest.php
index 52963e6..9fe890d 100644
--- a/tests/LanguageServerTest.php
+++ b/tests/LanguageServerTest.php
@@ -5,6 +5,7 @@ namespace LanguageServer\Tests;
 
 use PHPUnit\Framework\TestCase;
 use LanguageServer\LanguageServer;
+use LanguageServer\Options;
 use LanguageServer\Protocol\{
     Message,
     ClientCapabilities,
@@ -29,7 +30,7 @@ class LanguageServerTest extends TestCase
     public function testInitialize()
     {
         $server = new LanguageServer(new MockProtocolStream, new MockProtocolStream);
-        $result = $server->initialize(new ClientCapabilities, __DIR__, getmypid())->wait();
+        $result = $server->initialize(new ClientCapabilities, __DIR__, getmypid(), new Options)->wait();
 
         $serverCapabilities = new ServerCapabilities();
         $serverCapabilities->textDocumentSync = TextDocumentSyncKind::FULL;
@@ -60,14 +61,14 @@ class LanguageServerTest extends TestCase
                 if ($msg->body->params->type === MessageType::ERROR) {
                     $promise->reject(new Exception($msg->body->params->message));
                 } else if (preg_match('/All \d+ PHP files parsed/', $msg->body->params->message)) {
-                    $promise->fulfill();
+                    $promise->fulfill(true);
                 }
             }
         });
         $server = new LanguageServer($input, $output);
         $capabilities = new ClientCapabilities;
-        $server->initialize($capabilities, realpath(__DIR__ . '/../fixtures'), getmypid());
-        $promise->wait();
+        $server->initialize($capabilities, realpath(__DIR__ . '/../fixtures'), getmypid(), new Options);
+        $this->assertTrue($promise->wait());
     }
 
     public function testIndexingWithFilesAndContentRequests()
@@ -114,9 +115,34 @@ class LanguageServerTest extends TestCase
         $capabilities = new ClientCapabilities;
         $capabilities->xfilesProvider = true;
         $capabilities->xcontentProvider = true;
-        $server->initialize($capabilities, $rootPath, getmypid());
+        $server->initialize($capabilities, $rootPath, getmypid(), new Options);
         $promise->wait();
         $this->assertTrue($filesCalled);
         $this->assertTrue($contentCalled);
     }
+
+    public function testIndexingMultipleFileTypes()
+    {
+        $promise = new Promise;
+        $input = new MockProtocolStream;
+        $output = new MockProtocolStream;
+        $options = new Options;
+        $options->setFileTypes([
+            '.php',
+            '.inc'
+        ]);
+        $output->on('message', function (Message $msg) use ($promise, &$allFilesParsed) {
+            if ($msg->body->method === 'window/logMessage' && $promise->state === Promise::PENDING) {
+                if ($msg->body->params->type === MessageType::ERROR) {
+                    $promise->reject(new Exception($msg->body->params->message));
+                } elseif (preg_match('/All \d+ PHP files parsed/', $msg->body->params->message)) {
+                    $promise->fulfill(true);
+                }
+            }
+        });
+        $server = new LanguageServer($input, $output);
+        $capabilities = new ClientCapabilities;
+        $server->initialize($capabilities, realpath(__DIR__ . '/../fixtures'), getmypid(), $options);
+        $this->assertTrue($promise->wait());
+    }
 }
diff --git a/tests/OptionsTest.php b/tests/OptionsTest.php
new file mode 100644
index 0000000..04b2869
--- /dev/null
+++ b/tests/OptionsTest.php
@@ -0,0 +1,45 @@
+<?php
+declare(strict_types=1);
+
+namespace LanguageServer\Tests;
+
+use LanguageServer\Options;
+use PHPUnit\Framework\TestCase;
+
+class OptionsTest extends TestCase
+{
+    public function testFileTypesOption()
+    {
+        $expected = [
+            '.php',
+            '.valid'
+        ];
+
+        $options = new Options;
+        $options->setFileTypes([
+            '.php',
+            false,
+            12345,
+            '.valid'
+        ]);
+
+        $this->assertSame($expected, $options->fileTypes);
+    }
+
+    public function testConvertFileSize()
+    {
+        $options = new Options();
+
+        $options->setFileSizeLimit('150K');
+        $this->assertEquals(150000, $options->fileSizeLimit);
+
+        $options->setFileSizeLimit('15M');
+        $this->assertEquals(15000000, $options->fileSizeLimit);
+
+        $options->setFileSizeLimit('15G');
+        $this->assertEquals(15000000000, $options->fileSizeLimit);
+
+        $options->setFileSizeLimit('-1');
+        $this->assertEquals(PHP_INT_MAX, $options->fileSizeLimit);
+    }
+}