diff --git a/src/ImageResult.php b/src/ImageResult.php
index ecb9a4c..7141572 100644
--- a/src/ImageResult.php
+++ b/src/ImageResult.php
@@ -4,6 +4,13 @@
 
 final readonly class ImageResult
 {
+    /**
+     * @param  float|null  $psnr  Peak signal-to-noise ratio in decibels between the
+     *                            input and the output, returned by optimize and convert.
+     *                            Higher means closer to the input. Null when the API
+     *                            does not send the field (resize, thumbnail) or when
+     *                            the loss cannot be measured.
+     */
     public function __construct(
         public string $bytes,
         public string $format,
@@ -11,6 +18,7 @@ public function __construct(
         public int $size,
         public int $width,
         public int $height,
+        public ?float $psnr = null,
     ) {}
 
     /**
@@ -18,6 +26,8 @@ public function __construct(
      */
     public static function fromResponse(array $data): self
     {
+        $psnr = data_get($data, 'psnr');
+
         return new self(
             bytes: (string) base64_decode((string) data_get($data, 'output.data'), true),
             format: (string) data_get($data, 'format'),
@@ -25,6 +35,7 @@ public static function fromResponse(array $data): self
             size: (int) data_get($data, 'size'),
             width: (int) data_get($data, 'width'),
             height: (int) data_get($data, 'height'),
+            psnr: $psnr === null ? null : (float) $psnr,
         );
     }
 }
diff --git a/tests/ClientTest.php b/tests/ClientTest.php
index c9ed9dd..86a0f0a 100644
--- a/tests/ClientTest.php
+++ b/tests/ClientTest.php
@@ -8,6 +8,7 @@
 use MathiasGrimm\GlimpsePhp\ForbiddenException;
 use MathiasGrimm\GlimpsePhp\ImageFormat;
 use MathiasGrimm\GlimpsePhp\ImageInfo;
+use MathiasGrimm\GlimpsePhp\ImageResult;
 use MathiasGrimm\GlimpsePhp\RateLimitException;
 use MathiasGrimm\GlimpsePhp\SizeEstimate;
 use MathiasGrimm\GlimpsePhp\Tests\Fixtures\Images;
@@ -30,7 +31,7 @@ function client(Factory $http, Closure|string|null $token = 'test-token', string
 }
 
 test('convert posts the base64 envelope and returns a decoded ImageResult', function () {
-    $http = fakeHttp(['*/v1/convert' => Factory::response(fakeTransformResponse())]);
+    $http = fakeHttp(['*/v1/convert' => Factory::response(fakeTransformResponse(overrides: ['psnr' => 41.27]))]);
 
     $result = client($http)->convert(Images::png(), ImageFormat::Jpg);
 
@@ -38,7 +39,8 @@ function client(Factory $http, Closure|string|null $token = 'test-token', string
         ->and($result->format)->toBe(ImageFormat::Jpg->value)
         ->and($result->mimeType)->toBe('image/jpeg')
         ->and($result->width)->toBe(1280)
-        ->and($result->height)->toBe(720);
+        ->and($result->height)->toBe(720)
+        ->and($result->psnr)->toBe(41.27);
 
     $http->assertSent(function (Request $request) {
         return $request->url() === 'https://glimpseimg.com/api/v1/convert'
@@ -49,6 +51,33 @@ function client(Factory $http, Closure|string|null $token = 'test-token', string
     });
 });
 
+test('a null psnr in the response stays null', function () {
+    $http = fakeHttp(['*/v1/optimize' => Factory::response(fakeTransformResponse(overrides: ['psnr' => null]))]);
+
+    expect(client($http)->optimize(Images::png())->psnr)->toBeNull();
+});
+
+test('a response without a psnr field maps to a null psnr', function () {
+    // Resize and thumbnail responses do not carry the field at all.
+    $http = fakeHttp(['*/v1/resize' => Factory::response(fakeTransformResponse())]);
+
+    expect(client($http)->resize(Images::png(), width: 800)->psnr)->toBeNull();
+});
+
+test('an integer psnr in the response is cast to float', function () {
+    $http = fakeHttp(['*/v1/optimize' => Factory::response(fakeTransformResponse(overrides: ['psnr' => 42]))]);
+
+    expect(client($http)->optimize(Images::png())->psnr)->toBe(42.0);
+});
+
+test('the six-argument constructor stays valid and defaults psnr to null', function () {
+    // Locks backward compatibility: callers built against pre-3.1 must keep
+    // working without passing psnr.
+    $result = new ImageResult('bytes', 'jpg', 'image/jpeg', 100, 20, 10);
+
+    expect($result->psnr)->toBeNull();
+});
+
 test('convert sends optimize and quality when given', function () {
     $http = fakeHttp(['*/v1/convert' => Factory::response(fakeTransformResponse())]);
 
diff --git a/tests/Pest.php b/tests/Pest.php
index ccab4f9..5579e9f 100644
--- a/tests/Pest.php
+++ b/tests/Pest.php
@@ -68,11 +68,12 @@ function fakeInfoResponse(array $overrides = []): array
 /**
  * A canned successful transform-endpoint response envelope.
  *
+ * @param  array<string, mixed>  $overrides
  * @return array{data: array<string, mixed>}
  */
-function fakeTransformResponse(string $format = 'jpg', string $mimeType = 'image/jpeg'): array
+function fakeTransformResponse(string $format = 'jpg', string $mimeType = 'image/jpeg', array $overrides = []): array
 {
-    return ['data' => [
+    return ['data' => $overrides + [
         'output' => ['type' => 'BASE64', 'data' => Images::JPG_BASE64],
         'format' => $format,
         'mime_type' => $mimeType,