diff --git a/README.md b/README.md
index be58a843..1fa1d30c 100644
--- a/README.md
+++ b/README.md
@@ -19,6 +19,7 @@ $ composer require localheinz/json-normalizer
 
 This package comes with the following normalizers:
 
+* [`Localheinz\Json\Normalizer\CallableNormalizer`](#callablenormalizer)
 * [`Localheinz\Json\Normalizer\FinalNewLineNormalizer`](#finalnewlinenormalizer)
 * [`Localheinz\Json\Normalizer\IndentNormalizer`](#indentnormalizer)
 * [`Localheinz\Json\Normalizer\JsonEncodeNormalizer`](#jsonencodenormalizer)
@@ -26,6 +27,41 @@ This package comes with the following normalizers:
 
 :bulb: All of these normalizers implement the `Localheinz\Json\Normalizer\NormalizerInterface`. 
 
+### `CallableNormalizer`
+
+If you want to normalize a JSON file with a `callable`, you can use the `CallableNormalizer`.
+
+```php
+use Localheinz\Json\Normalizer;
+
+$json = <<<'JSON'
+{
+    "name": "Andreas Möller",
+    "url": "https://localheinz.com"
+}
+JSON;
+
+$callable = function (string $json): string {
+    $decoded = json_decode($json);
+
+    foreach (get_object_vars($decoded) as $name => $value) {
+        if ('https://localheinz.com' !== $value) {
+            continue;
+        }
+        
+        $decoded->{$name} .= '/open-source/';
+    }
+
+    return json_encode($decoded);
+};
+
+$normalizer = new Normalizer\CallableNormalizer($callable);
+
+$normalized = $normalizer->normalize($json);
+```
+
+The normalized version will now have the callable applied to it.
+
 ### `FinalNewLineNormalizer`
 
 If you want to ensure that a JSON file has a single final new line, you can use the `FinalNewLineNormalizer`.
diff --git a/src/CallableNormalizer.php b/src/CallableNormalizer.php
new file mode 100644
index 00000000..fbc41800
--- /dev/null
+++ b/src/CallableNormalizer.php
@@ -0,0 +1,41 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * Copyright (c) 2018 Andreas Möller.
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE file that was distributed with this source code.
+ *
+ * @see https://github.com/localheinz/json-normalizer
+ */
+
+namespace Localheinz\Json\Normalizer;
+
+final class CallableNormalizer implements NormalizerInterface
+{
+    /**
+     * @var callable
+     */
+    private $callable;
+
+    public function __construct(callable $callable)
+    {
+        $this->callable = $callable;
+    }
+
+    public function normalize(string $json): string
+    {
+        if (null === \json_decode($json) && JSON_ERROR_NONE !== \json_last_error()) {
+            throw new \InvalidArgumentException(\sprintf(
+                '"%s" is not valid JSON.',
+                $json
+            ));
+        }
+
+        $callable = $this->callable;
+
+        return $callable($json);
+    }
+}
diff --git a/test/Unit/CallableNormalizerTest.php b/test/Unit/CallableNormalizerTest.php
new file mode 100644
index 00000000..5d835036
--- /dev/null
+++ b/test/Unit/CallableNormalizerTest.php
@@ -0,0 +1,86 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * Copyright (c) 2018 Andreas Möller.
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE file that was distributed with this source code.
+ *
+ * @see https://github.com/localheinz/json-normalizer
+ */
+
+namespace Localheinz\Json\Normalizer\Test\Unit;
+
+use Localheinz\Json\Normalizer\CallableNormalizer;
+
+final class CallableNormalizerTest extends AbstractNormalizerTestCase
+{
+    /**
+     * @dataProvider providerCallable
+     *
+     * @param callable $callable
+     */
+    public function testNormalizePassesJsonThroughCallable(callable $callable)
+    {
+        $json = <<<'JSON'
+{
+    "name": "Andreas Möller",
+    "url": "https://localheinz.com",
+    "level": 1
+}
+JSON;
+
+        $normalized = $callable($json);
+
+        $normalizer = new CallableNormalizer($callable);
+
+        $this->assertSame($normalized, $normalizer->normalize($json));
+    }
+
+    public function providerCallable(): \Generator
+    {
+        $values = [
+            'closure' => function (string $json): string {
+                $decoded = \json_decode($json);
+
+                foreach (\get_object_vars($decoded) as $name => $value) {
+                    if (!\is_int($value)) {
+                        continue;
+                    }
+
+                    $decoded->{$name} = $value + 1;
+                }
+
+                return \json_encode($decoded);
+            },
+            'function-name' => 'trim',
+            'method' => [
+                self::class,
+                'callable',
+            ],
+        ];
+
+        foreach ($values as $key => $value) {
+            yield $key => [
+                $value,
+            ];
+        }
+    }
+
+    public static function callable(string $json): string
+    {
+        $decoded = \json_decode($json);
+
+        foreach (\get_object_vars($decoded) as $name => $value) {
+            if (!\is_string($value)) {
+                continue;
+            }
+
+            $decoded->{$name} = $value . ' (ok)';
+        }
+
+        return \json_encode($decoded);
+    }
+}