diff --git a/README.md b/README.md
index 5c3faa1..4fc3cfb 100644
--- a/README.md
+++ b/README.md
@@ -179,7 +179,16 @@ Use a boolean, or tuple of two floats, or the comma separated string equivalent.
 
 You can also use the following keywords: `tl` (top left), `tr` (top right), `bl` (bottom left), `br` (bottom right), `l`, `r`, `t` or `b`. This will set the percentage to 0 or 100 for the appropriate axis.
 
-If crop is `False`, the image will be resized so that it will cover the requested ratio but not cropped down. This is useful when you want to handle positioning in CSS using `object-fit`.
+If crop is `False`, the image will be resized so that it will cover the requested ratio but not cropped down.
+This is useful when you want to handle positioning in CSS using `object-fit`.
+
+#### `cover`
+
+Whether to resize the image to cover the requested ratio or to contain it (when not cropping).
+
+The default is `True`, meaning the image will be resized down to cover the requested ratio (which means the image dimensions may be larger than the requested dimensions).
+
+To rezise the image to always fit within the requested dimensions, set `cover=False`.
 
 #### `focal_window`
 
diff --git a/easy_images/core.py b/easy_images/core.py
index fdf500e..09f7fd4 100644
--- a/easy_images/core.py
+++ b/easy_images/core.py
@@ -17,13 +17,13 @@
     from easy_images.models import EasyImage
 
 
-format_map = {"avif": "image/avif", "webp": "image/webp"}
-
+format_map = {"avif": "image/avif", "webp": "image/webp", "jpeg": "image/jpeg"}
 
 option_defaults: ImgOptions = {
     "quality": 80,
     "ratio": "video",
     "crop": True,
+    "cover": False,
     "densities": [2],
     "format": "webp",
 }
diff --git a/easy_images/engine.py b/easy_images/engine.py
index a202c4d..a6f22c2 100644
--- a/easy_images/engine.py
+++ b/easy_images/engine.py
@@ -22,6 +22,7 @@ def scale_image(
     target: tuple[int, int],
     /,
     crop: tuple[float, float] | bool | None = None,
+    cover: bool = True,
     focal_window: tuple[float, float, float, float] | None = None,
 ):
     """
@@ -30,8 +31,15 @@ def scale_image(
     """
     w, h = img.width, img.height
 
-    # Size image down to cover the dimensions
-    scale = max(target[0] / w, target[1] / h)
+    if crop:
+        cover = True
+
+    if cover:
+        # Size image down to cover the dimensions
+        scale = max(target[0] / w, target[1] / h)
+    else:
+        # Size image to contain the dimensions
+        scale = min(target[0] / w, target[1] / h)
 
     # Focal window scaling
     if focal_window:
@@ -44,7 +52,10 @@ def scale_image(
         if f_right - f_left > target[0] and f_bottom - f_top > target[1]:
             img = img.extract_area(f_left, f_top, f_right - f_left, f_bottom - f_top)
             w, h = img.width, h
-            scale = max(target[0] / w, target[1] / h)
+            if cover:
+                scale = max(target[0] / w, target[1] / h)
+            else:
+                scale = min(target[0] / w, target[1] / h)
             focal_window = None
         # Otherwise, if cropping then set the crop focal point to the center of the
         # focal window.
diff --git a/easy_images/models.py b/easy_images/models.py
index 4b4c2b6..8a8a8da 100644
--- a/easy_images/models.py
+++ b/easy_images/models.py
@@ -137,6 +137,8 @@ def build(
                     scale_args["focal_window"] = options.window
                 if options.crop:
                     scale_args["crop"] = options.crop
+                if options.cover:
+                    scale_args["cover"] = options.cover
                 img = engine.scale_image(source_img, size, **scale_args)
             else:
                 img = source_img
diff --git a/easy_images/options.py b/easy_images/options.py
index c75b862..17ee057 100644
--- a/easy_images/options.py
+++ b/easy_images/options.py
@@ -39,15 +39,18 @@
 
 
 class ParsedOptions:
-    __slots__ = ("quality", "crop", "window", "width", "ratio", "mimetype")
+    __slots__ = ("quality", "crop", "cover", "window", "width", "ratio", "mimetype")
 
     quality: int
     crop: tuple[float, float] | None
+    cover: bool
     window: tuple[float, float, float, float] | None
     width: int | None
     ratio: float | None
     mimetype: str | None
 
+    _defaults = {"cover": True}
+
     def __init__(self, bound=None, string="", /, **options):
         if string:
             for part in smart_split(string):
@@ -64,9 +67,12 @@ def __init__(self, bound=None, string="", /, **options):
                 value = value.resolve(context)
             if value or value == 0:
                 parse_func = getattr(self, f"parse_{key}")
-                setattr(self, key, parse_func(value, **options))
+                value = parse_func(value, **options)
+            elif key in self._defaults:
+                value = self._defaults[key]
             else:
-                setattr(self, key, 80 if key == "quality" else None)
+                value = 80 if key == "quality" else None
+            setattr(self, key, value)
 
     @classmethod
     def from_str(cls, s: str):
@@ -103,6 +109,12 @@ def parse_crop(value, **options) -> tuple[float, float]:
                 pass
         raise ValueError(f"Invalid crop value {value}")
 
+    @staticmethod
+    def parse_cover(value, **options) -> bool:
+        if not isinstance(value, bool):
+            raise ValueError(f"Invalid cover value {value}")
+        return value
+
     @staticmethod
     def parse_window(value, **options) -> tuple[float, float, float, float]:
         if isinstance(value, str):
@@ -166,7 +178,11 @@ def size(self):
         return self.width, int(self.width / self.ratio)
 
     def to_dict(self):
-        return {key: getattr(self, key) for key in self.__slots__}
+        return {
+            key: getattr(self, key)
+            for key in self.__slots__
+            if key not in self._defaults or getattr(self, key) != self._defaults[key]
+        }
 
     def source_x(self, source_x: int):
         if self.window:
diff --git a/easy_images/types_.py b/easy_images/types_.py
index 9878500..afef0ae 100644
--- a/easy_images/types_.py
+++ b/easy_images/types_.py
@@ -32,17 +32,17 @@
     "golden",
     "golden_vertical",
 ]
+FitChoices: TypeAlias = Literal["contain", "cover"]
 
 alternative_re = re.compile(r"^(\d+w|\d(?:\.\d)?x)$")
 
 BuildChoices: TypeAlias = Literal["srcset", "src", None]
 
-format_map = {"avif": "image/avif", "webp": "image/webp", "jpeg": "image/jpeg"}
-
 
 class Options(TypedDict, total=False):
     quality: int
     crop: tuple[float, float] | CropChoices | bool
+    cover: bool
     window: tuple[float, float, float, float] | None
     width: int | WidthChoices | None
     ratio: float | tuple[float, float] | RatioChoices | None
diff --git a/tests/test_engine.py b/tests/test_engine.py
index 5277f0c..abf1492 100644
--- a/tests/test_engine.py
+++ b/tests/test_engine.py
@@ -5,7 +5,7 @@
     SimpleUploadedFile,
 )
 
-from easy_images.engine import efficient_load
+from easy_images.engine import efficient_load, scale_image
 from easy_images.options import ParsedOptions
 from pyvips import Image
 
@@ -51,3 +51,13 @@ def test_efficient_load_from_memory():
     file = SimpleUploadedFile("test.jpg", image.write_to_buffer(".jpg[Q=90]"))
     e_image = efficient_load(file, [ParsedOptions(width=100, ratio="video")])
     assert (e_image.width, e_image.height) == (500, 500)
+
+
+def test_scale():
+    source = Image.black(1000, 1000)
+    scaled_cover = scale_image(source, (400, 500))
+    assert (scaled_cover.width, scaled_cover.height) == (500, 500)
+    scaled = scale_image(source, (400, 500), cover=False)
+    assert (scaled.width, scaled.height) == (400, 400)
+    cropped = scale_image(source, (400, 500), crop=True)
+    assert (cropped.width, cropped.height) == (400, 500)
diff --git a/tests/test_options.py b/tests/test_options.py
index 59df9b5..3368c66 100644
--- a/tests/test_options.py
+++ b/tests/test_options.py
@@ -50,3 +50,14 @@ def test_hash():
         ParsedOptions(quality=80).hash().hexdigest()
         == "cce6431a80fe3a84c7ea9f6c5293cbce4ed8848349bb0f2182eb6bb0d7a19f78"
     )
+
+
+def test_str():
+    assert (
+        str(ParsedOptions(width=100, ratio="video"))
+        == '{"crop": null, "mimetype": null, "quality": 80, "ratio": 1.7777777777777777, "width": 100, "window": null}'
+    )
+    assert (
+        str(ParsedOptions(width=100, cover=False))
+        == '{"cover": false, "crop": null, "mimetype": null, "quality": 80, "ratio": null, "width": 100, "window": null}'
+    )