diff --git a/CHANGELOG.md b/CHANGELOG.md
index e418939db..238c9cfb6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,7 +11,8 @@
     * Added `FormFlash` class to contain AJAX uploaded files in more reliable way
     * Added `FormFlashFile` class which implements `UploadedFileInterface` from PSR-7
 1. [](#improved)
-    * Improve Flex storage
+    * Improved Flex storage classes
+    * Improved `Grav\Framework\File\Formatter` classes to have abstract parent class and some useful methods
 1. [](#bugfix)
     * Fixed handling of `append_url_extension` inside of `Page::templateFormat()` [#2264](https://github.com/getgrav/grav/issues/2264) 
     * Fixed a broken language string [#2261](https://github.com/getgrav/grav/issues/2261)
diff --git a/system/src/Grav/Framework/File/Formatter/AbstractFormatter.php b/system/src/Grav/Framework/File/Formatter/AbstractFormatter.php
new file mode 100644
index 000000000..852f4e5b2
--- /dev/null
+++ b/system/src/Grav/Framework/File/Formatter/AbstractFormatter.php
@@ -0,0 +1,106 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * @package    Grav\Framework\File\Formatter
+ *
+ * @copyright  Copyright (C) 2015 - 2018 Trilby Media, LLC. All rights reserved.
+ * @license    MIT License; see LICENSE file for details.
+ */
+
+namespace Grav\Framework\File\Formatter;
+
+abstract class AbstractFormatter implements FormatterInterface
+{
+    /** @var array */
+    private $config;
+
+    /**
+     * IniFormatter constructor.
+     * @param array $config
+     */
+    public function __construct(array $config = [])
+    {
+        $this->config = $config;
+    }
+
+    /**
+     * @return string
+     */
+    public function serialize(): string
+    {
+        return serialize($this->doSerialize());
+    }
+
+    /**
+     * @param string $serialized
+     */
+    public function unserialize($serialized): void
+    {
+        $this->doUnserialize(unserialize($serialized, false));
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getDefaultFileExtension(): string
+    {
+        $extensions = $this->getSupportedFileExtensions();
+
+        // Call fails on bad configuration.
+        return reset($extensions);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getSupportedFileExtensions(): array
+    {
+        // Call fails on bad configuration.
+        return $this->getConfig('file_extension');
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    abstract public function encode($data): string;
+
+    /**
+     * {@inheritdoc}
+     */
+    abstract public function decode($data);
+
+    /**
+     * Get either full configuration or a single option.
+     *
+     * @param string|null $name Configuration option (optional)
+     * @return mixed
+     */
+    protected function getConfig(string $name = null)
+    {
+        if (null !== $name) {
+            return $this->config[$name] ?? null;
+        }
+
+        return $this->config;
+    }
+
+    /**
+     * @return array
+     */
+    protected function doSerialize(): array
+    {
+        return ['config' => $this->config];
+    }
+
+    /**
+     * Note: if overridden, make sure you call parent::doUnserialize()
+     *
+     * @param array $serialized
+     */
+    protected function doUnserialize(array $serialized): void
+    {
+        $this->config = $serialized['config'];
+    }
+}
diff --git a/system/src/Grav/Framework/File/Formatter/CsvFormatter.php b/system/src/Grav/Framework/File/Formatter/CsvFormatter.php
index 7bc89bbcc..6c4421ffa 100644
--- a/system/src/Grav/Framework/File/Formatter/CsvFormatter.php
+++ b/system/src/Grav/Framework/File/Formatter/CsvFormatter.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * @package    Grav\Framework\File\Formatter
  *
@@ -9,50 +11,37 @@
 
 namespace Grav\Framework\File\Formatter;
 
-class CsvFormatter implements FormatterInterface
+class CsvFormatter extends AbstractFormatter
 {
-    /** @var array */
-    private $config;
-
     /**
      * IniFormatter constructor.
      * @param array $config
      */
     public function __construct(array $config = [])
     {
-        $this->config = $config + [
-                'file_extension' => ['.csv', '.tsv'],
-                'delimiter' => ','
-            ];
+        $config += [
+            'file_extension' => ['.csv', '.tsv'],
+            'delimiter' => ','
+        ];
+
+        parent::__construct($config);
+    }
+
+    /**
+     * Returns delimiter used to both encode and decode CSV.
+     *
+     * @return string
+     */
+    public function getDelimiter(): string
+    {
+        // Call fails on bad configuration.
+        return $this->getConfig('delimiter');
     }
 
     /**
      * {@inheritdoc}
      */
-    public function getDefaultFileExtension()
-    {
-        $extensions = $this->getSupportedFileExtensions();
-
-        return (string) reset($extensions);
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function getSupportedFileExtensions()
-    {
-        return (array) $this->config['file_extension'];
-    }
-
-    public function getDelimiter()
-    {
-        return $this->config['delimiter'];
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function encode($data, $delimiter = null)
+    public function encode($data, $delimiter = null): string
     {
         $delimiter = $delimiter ?? $this->getDelimiter();
         $header = array_keys(reset($lines));
@@ -71,7 +60,7 @@ class CsvFormatter implements FormatterInterface
     /**
      * {@inheritdoc}
      */
-    public function decode($data, $delimiter = null)
+    public function decode($data, $delimiter = null): array
     {
         $delimiter = $delimiter ?? $this->getDelimiter();
         $lines = preg_split('/\r\n|\r|\n/', $data);
diff --git a/system/src/Grav/Framework/File/Formatter/FormatterInterface.php b/system/src/Grav/Framework/File/Formatter/FormatterInterface.php
index 1149eb23e..04793461a 100644
--- a/system/src/Grav/Framework/File/Formatter/FormatterInterface.php
+++ b/system/src/Grav/Framework/File/Formatter/FormatterInterface.php
@@ -1,7 +1,9 @@
 <?php
 
+declare(strict_types=1);
+
 /**
- * @package    Grav\Framework\File\Formatter
+ * @package    Grav\Framework\File
  *
  * @copyright  Copyright (C) 2015 - 2018 Trilby Media, LLC. All rights reserved.
  * @license    MIT License; see LICENSE file for details.
@@ -9,7 +11,7 @@
 
 namespace Grav\Framework\File\Formatter;
 
-interface FormatterInterface
+interface FormatterInterface extends \Serializable
 {
     /**
      * Get default file extension from current formatter (with dot).
@@ -18,14 +20,14 @@ interface FormatterInterface
      *
      * @return string File extension (can be empty).
      */
-    public function getDefaultFileExtension();
+    public function getDefaultFileExtension(): string;
 
     /**
      * Get file extensions supported by current formatter (with dot).
      *
      * @return string[]
      */
-    public function getSupportedFileExtensions();
+    public function getSupportedFileExtensions(): array;
 
     /**
      * Encode data into a string.
@@ -33,13 +35,13 @@ interface FormatterInterface
      * @param array $data
      * @return string
      */
-    public function encode($data);
+    public function encode($data): string;
 
     /**
      * Decode a string into data.
      *
      * @param string $data
-     * @return array
+     * @return mixed
      */
     public function decode($data);
-}
\ No newline at end of file
+}
diff --git a/system/src/Grav/Framework/File/Formatter/IniFormatter.php b/system/src/Grav/Framework/File/Formatter/IniFormatter.php
index 754edf5f8..e81f599ef 100644
--- a/system/src/Grav/Framework/File/Formatter/IniFormatter.php
+++ b/system/src/Grav/Framework/File/Formatter/IniFormatter.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * @package    Grav\Framework\File\Formatter
  *
@@ -9,44 +11,25 @@
 
 namespace Grav\Framework\File\Formatter;
 
-class IniFormatter implements FormatterInterface
+class IniFormatter extends AbstractFormatter
 {
-    /** @var array */
-    private $config;
-
     /**
      * IniFormatter constructor.
      * @param array $config
      */
     public function __construct(array $config = [])
     {
-        $this->config = $config + [
-                'file_extension' => '.ini'
-            ];
+        $config += [
+            'file_extension' => '.ini'
+        ];
+
+        parent::__construct($config);
     }
 
     /**
      * {@inheritdoc}
      */
-    public function getDefaultFileExtension()
-    {
-        $extensions = $this->getSupportedFileExtensions();
-
-        return (string) reset($extensions);
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function getSupportedFileExtensions()
-    {
-        return (array) $this->config['file_extension'];
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function encode($data)
+    public function encode($data): string
     {
         $string = '';
         foreach ($data as $key => $value) {
@@ -63,7 +46,7 @@ class IniFormatter implements FormatterInterface
     /**
      * {@inheritdoc}
      */
-    public function decode($data)
+    public function decode($data): array
     {
         $decoded = @parse_ini_string($data);
 
diff --git a/system/src/Grav/Framework/File/Formatter/JsonFormatter.php b/system/src/Grav/Framework/File/Formatter/JsonFormatter.php
index 3ff3adfe7..7e1ac8e8d 100644
--- a/system/src/Grav/Framework/File/Formatter/JsonFormatter.php
+++ b/system/src/Grav/Framework/File/Formatter/JsonFormatter.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * @package    Grav\Framework\File\Formatter
  *
@@ -9,47 +11,70 @@
 
 namespace Grav\Framework\File\Formatter;
 
-class JsonFormatter implements FormatterInterface
+class JsonFormatter extends AbstractFormatter
 {
-    /** @var array */
-    private $config;
-
     public function __construct(array $config = [])
     {
-        $this->config = $config + [
+        $config += [
             'file_extension' => '.json',
             'encode_options' => 0,
-            'decode_assoc' => true
+            'decode_assoc' => true,
+            'decode_depth' => 512,
+            'decode_options' => 0
         ];
+
+        parent::__construct($config);
+    }
+
+    /**
+     * Returns options used in encode() function.
+     *
+     * @return int
+     */
+    public function getEncodeOptions(): int
+    {
+        return $this->getConfig('encode_options');
+    }
+
+    /**
+     * Returns options used in decode() function.
+     *
+     * @return int
+     */
+    public function getDecodeOptions(): int
+    {
+        return $this->getConfig('decode_options');
+    }
+
+    /**
+     * Returns recursion depth used in decode() function.
+     *
+     * @return int
+     */
+    public function getDecodeDepth(): int
+    {
+        return $this->getConfig('decode_depth');
+    }
+
+    /**
+     * Returns true if JSON objects will be converted into associative arrays.
+     *
+     * @return bool
+     */
+    public function getDecodeAssoc(): bool
+    {
+        return $this->getConfig('decode_assoc');
     }
 
     /**
      * {@inheritdoc}
      */
-    public function getDefaultFileExtension()
+    public function encode($data): string
     {
-        $extensions = $this->getSupportedFileExtensions();
+        $encoded = @json_encode($data, $this->getEncodeOptions());
 
-        return (string) reset($extensions);
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function getSupportedFileExtensions()
-    {
-        return (array) $this->config['file_extension'];
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function encode($data)
-    {
-        $encoded = @json_encode($data, $this->config['encode_options']);
-
-        if ($encoded === false) {
-            throw new \RuntimeException('Encoding JSON failed');
+        if ($encoded === false && json_last_error() !== JSON_ERROR_NONE) {
+            throw new \RuntimeException('Encoding JSON failed: ' . json_last_error_msg());
         }
 
         return $encoded;
@@ -60,10 +85,10 @@ class JsonFormatter implements FormatterInterface
      */
     public function decode($data)
     {
-        $decoded = @json_decode($data, $this->config['decode_assoc']);
+        $decoded = @json_decode($data, $this->getDecodeAssoc(), $this->getDecodeDepth(), $this->getDecodeOptions());
 
-        if ($decoded === false) {
-            throw new \RuntimeException('Decoding JSON failed');
+        if (null === $decoded && json_last_error() !== JSON_ERROR_NONE) {
+            throw new \RuntimeException('Decoding JSON failed: ' . json_last_error_msg());
         }
 
         return $decoded;
diff --git a/system/src/Grav/Framework/File/Formatter/MarkdownFormatter.php b/system/src/Grav/Framework/File/Formatter/MarkdownFormatter.php
index 181e4477e..348c84890 100644
--- a/system/src/Grav/Framework/File/Formatter/MarkdownFormatter.php
+++ b/system/src/Grav/Framework/File/Formatter/MarkdownFormatter.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * @package    Grav\Framework\File\Formatter
  *
@@ -9,16 +11,16 @@
 
 namespace Grav\Framework\File\Formatter;
 
-class MarkdownFormatter implements FormatterInterface
+use Grav\Framework\File\Interfaces\FileFormatterInterface;
+
+class MarkdownFormatter extends AbstractFormatter
 {
-    /** @var array */
-    private $config;
     /** @var FormatterInterface */
     private $headerFormatter;
 
-    public function __construct(array $config = [], FormatterInterface $headerFormatter = null)
+    public function __construct(array $config = [], FileFormatterInterface $headerFormatter = null)
     {
-        $this->config = $config + [
+        $config += [
             'file_extension' => '.md',
             'header' => 'header',
             'body' => 'markdown',
@@ -26,34 +28,58 @@ class MarkdownFormatter implements FormatterInterface
             'yaml' => ['inline' => 20]
         ];
 
-        $this->headerFormatter = $headerFormatter ?: new YamlFormatter($this->config['yaml']);
+        parent::__construct($config);
+
+        $this->headerFormatter = $headerFormatter ?: new YamlFormatter($config['yaml']);
+    }
+
+    /**
+     * Returns header field used in both encode() and decode().
+     *
+     * @return string
+     */
+    public function getHeaderField(): string
+    {
+        return $this->getConfig('header');
+    }
+
+    /**
+     * Returns body field used in both encode() and decode().
+     *
+     * @return string
+     */
+    public function getBodyField(): string
+    {
+        return $this->getConfig('body');
+    }
+
+    /**
+     * Returns raw field used in both encode() and decode().
+     *
+     * @return string
+     */
+    public function getRawField(): string
+    {
+        return $this->getConfig('raw');
+    }
+
+    /**
+     * Returns header formatter object used in both encode() and decode().
+     *
+     * @return FileFormatterInterface
+     */
+    public function getHeaderFormatter(): FileFormatterInterface
+    {
+        return $this->headerFormatter;
     }
 
     /**
      * {@inheritdoc}
      */
-    public function getDefaultFileExtension()
+    public function encode($data): string
     {
-        $extensions = $this->getSupportedFileExtensions();
-
-        return (string) reset($extensions);
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function getSupportedFileExtensions()
-    {
-        return (array) $this->config['file_extension'];
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function encode($data)
-    {
-        $headerVar = $this->config['header'];
-        $bodyVar = $this->config['body'];
+        $headerVar = $this->getHeaderField();
+        $bodyVar = $this->getBodyField();
 
         $header = isset($data[$headerVar]) ? (array) $data[$headerVar] : [];
         $body = isset($data[$bodyVar]) ? (string) $data[$bodyVar] : '';
@@ -61,7 +87,7 @@ class MarkdownFormatter implements FormatterInterface
         // Create Markdown file with YAML header.
         $encoded = '';
         if ($header) {
-            $encoded = "---\n" . trim($this->headerFormatter->encode($data['header'])) . "\n---\n\n";
+            $encoded = "---\n" . trim($this->getHeaderFormatter()->encode($data['header'])) . "\n---\n\n";
         }
         $encoded .= $body;
 
@@ -74,12 +100,13 @@ class MarkdownFormatter implements FormatterInterface
     /**
      * {@inheritdoc}
      */
-    public function decode($data)
+    public function decode($data): array
     {
-        $headerVar = $this->config['header'];
-        $bodyVar = $this->config['body'];
-        $rawVar = $this->config['raw'];
+        $headerVar = $this->getHeaderField();
+        $bodyVar = $this->getBodyField();
+        $rawVar = $this->getRawField();
 
+        // Define empty content
         $content = [
             $headerVar => [],
             $bodyVar => ''
@@ -100,7 +127,7 @@ class MarkdownFormatter implements FormatterInterface
             if ($rawVar) {
                 $content[$rawVar] = $frontmatter;
             }
-            $content[$headerVar] = $this->headerFormatter->decode($frontmatter);
+            $content[$headerVar] = $this->getHeaderFormatter()->decode($frontmatter);
             $content[$bodyVar] = $matches[2];
         }
 
diff --git a/system/src/Grav/Framework/File/Formatter/SerializeFormatter.php b/system/src/Grav/Framework/File/Formatter/SerializeFormatter.php
index 4e9ef9773..d1c4fa970 100644
--- a/system/src/Grav/Framework/File/Formatter/SerializeFormatter.php
+++ b/system/src/Grav/Framework/File/Formatter/SerializeFormatter.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * @package    Grav\Framework\File\Formatter
  *
@@ -9,44 +11,38 @@
 
 namespace Grav\Framework\File\Formatter;
 
-class SerializeFormatter implements FormatterInterface
+class SerializeFormatter extends AbstractFormatter
 {
-    /** @var array */
-    private $config;
-
     /**
      * IniFormatter constructor.
      * @param array $config
      */
     public function __construct(array $config = [])
     {
-        $this->config = $config + [
-                'file_extension' => '.ser'
-            ];
+        $config += [
+            'file_extension' => '.ser',
+            'decode_options' => ['allowed_classes' => [\stdClass::class]]
+        ];
+
+        parent::__construct($config);
     }
 
     /**
-     * {@inheritdoc}
+     * Returns options used in decode().
+     *
+     * By default only allow stdClass class.
+     *
+     * @return array|bool
      */
-    public function getDefaultFileExtension()
+    public function getOptions()
     {
-        $extensions = $this->getSupportedFileExtensions();
-
-        return (string) reset($extensions);
+        return $this->getConfig('decode_options');
     }
 
     /**
      * {@inheritdoc}
      */
-    public function getSupportedFileExtensions()
-    {
-        return (array) $this->config['file_extension'];
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function encode($data)
+    public function encode($data): string
     {
         return serialize($this->preserveLines($data, ["\n", "\r"], ['\\n', '\\r']));
     }
@@ -56,9 +52,9 @@ class SerializeFormatter implements FormatterInterface
      */
     public function decode($data)
     {
-        $decoded = @unserialize($data);
+        $decoded = @unserialize($data, $this->getOptions());
 
-        if ($decoded === false) {
+        if ($decoded === false && $data !== serialize(false)) {
             throw new \RuntimeException('Decoding serialized data failed');
         }
 
@@ -73,7 +69,7 @@ class SerializeFormatter implements FormatterInterface
      * @param array $replace
      * @return mixed
      */
-    protected function preserveLines($data, $search, $replace)
+    protected function preserveLines($data, array $search, array $replace)
     {
         if (\is_string($data)) {
             $data = str_replace($search, $replace, $data);
diff --git a/system/src/Grav/Framework/File/Formatter/YamlFormatter.php b/system/src/Grav/Framework/File/Formatter/YamlFormatter.php
index 0a2ea04c1..78fde2b4a 100644
--- a/system/src/Grav/Framework/File/Formatter/YamlFormatter.php
+++ b/system/src/Grav/Framework/File/Formatter/YamlFormatter.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * @package    Grav\Framework\File\Formatter
  *
@@ -14,50 +16,63 @@ use Symfony\Component\Yaml\Exception\ParseException;
 use Symfony\Component\Yaml\Yaml as YamlParser;
 use RocketTheme\Toolbox\Compat\Yaml\Yaml as FallbackYamlParser;
 
-class YamlFormatter implements FormatterInterface
+class YamlFormatter extends AbstractFormatter
 {
-    /** @var array */
-    private $config;
-
     public function __construct(array $config = [])
     {
-        $this->config = $config + [
+        $config += [
             'file_extension' => '.yaml',
             'inline' => 5,
             'indent' => 2,
             'native' => true,
             'compat' => true
         ];
+
+        parent::__construct($config);
     }
 
     /**
-     * {@inheritdoc}
+     * @return int
      */
-    public function getDefaultFileExtension()
+    public function getInlineOption(): int
     {
-        $extensions = $this->getSupportedFileExtensions();
-
-        return (string) reset($extensions);
+        return $this->getConfig('inline');
     }
 
     /**
-     * {@inheritdoc}
+     * @return int
      */
-    public function getSupportedFileExtensions()
+    public function getIndentOption(): int
     {
-        return (array) $this->config['file_extension'];
+        return $this->getConfig('indent');
+    }
+
+    /**
+     * @return bool
+     */
+    public function useNativeDecoder(): bool
+    {
+        return $this->getConfig('native');
+    }
+
+    /**
+     * @return bool
+     */
+    public function useCompatibleDecoder(): bool
+    {
+        return $this->getConfig('compat');
     }
 
     /**
      * {@inheritdoc}
      */
-    public function encode($data, $inline = null, $indent = null)
+    public function encode($data, $inline = null, $indent = null): string
     {
         try {
-            return (string) YamlParser::dump(
+            return YamlParser::dump(
                 $data,
-                $inline ? (int) $inline : $this->config['inline'],
-                $indent ? (int) $indent : $this->config['indent'],
+                $inline ? (int) $inline : $this->getInlineOption(),
+                $indent ? (int) $indent : $this->getIndentOption(),
                 YamlParser::DUMP_EXCEPTION_ON_INVALID_TYPE
             );
         } catch (DumpException $e) {
@@ -68,10 +83,10 @@ class YamlFormatter implements FormatterInterface
     /**
      * {@inheritdoc}
      */
-    public function decode($data)
+    public function decode($data): array
     {
         // Try native PECL YAML PHP extension first if available.
-        if (\function_exists('yaml_parse') && $this->config['native']) {
+        if (\function_exists('yaml_parse') && $this->useNativeDecoder()) {
             // Safely decode YAML.
             $saved = @ini_get('yaml.decode_php');
             @ini_set('yaml.decode_php', 0);
@@ -79,14 +94,14 @@ class YamlFormatter implements FormatterInterface
             @ini_set('yaml.decode_php', $saved);
 
             if ($decoded !== false) {
-                return (array) $decoded;
+                return $decoded;
             }
         }
 
         try {
-            return (array) YamlParser::parse($data);
+            return YamlParser::parse($data);
         } catch (ParseException $e) {
-            if ($this->config['compat']) {
+            if ($this->useCompatibleDecoder()) {
                 return (array) FallbackYamlParser::parse($data);
             }