diff --git a/datasette/app.py b/datasette/app.py
index 6ea208e6..f86a14b5 100644
--- a/datasette/app.py
+++ b/datasette/app.py
@@ -1,6 +1,4 @@
 import asyncio
-import aiofiles
-from mimetypes import guess_type
 import collections
 import hashlib
 import json
@@ -38,6 +36,7 @@ from .utils import (
     sqlite_timelimit,
     to_css_class,
 )
+from .utils.asgi import asgi_static, asgi_send_html, asgi_send_json
 from .tracer import capture_traces, trace
 from .plugins import pm, DEFAULT_PLUGINS
 from .version import __version__
@@ -714,78 +713,3 @@ class Datasette:
         #             await database.table_counts(limit=60 * 60 * 1000)
 
         return app
-
-
-async def asgi_send_json(send, info, status=200, headers=None):
-    headers = headers or {}
-    await asgi_send(
-        send,
-        json.dumps(info),
-        status=status,
-        headers=headers,
-        content_type="application/json",
-    )
-
-
-async def asgi_send_html(send, html, status=200, headers=None):
-    headers = headers or {}
-    await asgi_send(
-        send, html, status=status, headers=headers, content_type="text/html"
-    )
-
-
-async def asgi_send(send, content, status, headers, content_type="text/plain"):
-    await asgi_start(send, status, headers, content_type)
-    await send({"type": "http.response.body", "body": content.encode("utf8")})
-
-
-async def asgi_start(send, status, headers, content_type="text/plain"):
-    # Remove any existing content-type header
-    headers = dict([(k, v) for k, v in headers.items() if k.lower() != "content-type"])
-    headers["content-type"] = content_type
-    await send(
-        {
-            "type": "http.response.start",
-            "status": status,
-            "headers": [
-                [key.encode("latin1"), value.encode("latin1")]
-                for key, value in headers.items()
-            ],
-        }
-    )
-
-
-def asgi_static(root_path, chunk_size=4096):
-    async def inner_static(scope, receive, send):
-        path = scope["url_route"]["kwargs"]["path"]
-        full_path = (Path(root_path) / path).absolute()
-        # Ensure full_path is within root_path to avoid weird "../" tricks
-        try:
-            full_path.relative_to(root_path)
-        except ValueError:
-            await asgi_send_html(send, "404", 404)
-            return
-        first = True
-        try:
-            async with aiofiles.open(full_path, mode="rb") as fp:
-                if first:
-                    await asgi_start(
-                        send, 200, {}, guess_type(str(full_path))[0] or "text/plain"
-                    )
-                    first = False
-                more_body = True
-                while more_body:
-                    chunk = await fp.read(chunk_size)
-                    more_body = len(chunk) == chunk_size
-                    await send(
-                        {
-                            "type": "http.response.body",
-                            "body": chunk,
-                            "more_body": more_body,
-                        }
-                    )
-        except FileNotFoundError:
-            await asgi_send_html(send, "404", 404)
-            return
-
-    return inner_static
diff --git a/datasette/utils.py b/datasette/utils/__init__.py
similarity index 100%
rename from datasette/utils.py
rename to datasette/utils/__init__.py
diff --git a/datasette/utils/asgi.py b/datasette/utils/asgi.py
new file mode 100644
index 00000000..14ade563
--- /dev/null
+++ b/datasette/utils/asgi.py
@@ -0,0 +1,244 @@
+import json
+from mimetypes import guess_type
+from sanic.views import HTTPMethodView
+from pathlib import Path
+import re
+import aiofiles
+
+
+class AsgiRouter:
+    def __init__(self, routes=None):
+        routes = routes or []
+        self.routes = [
+            # Compile any strings to regular expressions
+            ((re.compile(pattern) if isinstance(pattern, str) else pattern), view)
+            for pattern, view in routes
+        ]
+
+    async def __call__(self, scope, receive, send):
+        for regex, view in self.routes:
+            match = regex.match(scope["path"])
+            if match is not None:
+                new_scope = dict(scope, url_route={"kwargs": match.groupdict()})
+                try:
+                    return await view(new_scope, receive, send)
+                except Exception as exception:
+                    return await self.handle_500(scope, receive, send, exception)
+        return await self.handle_404(scope, receive, send)
+
+    async def handle_404(self, scope, receive, send):
+        await send(
+            {
+                "type": "http.response.start",
+                "status": 404,
+                "headers": [[b"content-type", b"text/html"]],
+            }
+        )
+        await send({"type": "http.response.body", "body": b"<h1>404</h1>"})
+
+    async def handle_500(self, scope, receive, send, exception):
+        await send(
+            {
+                "type": "http.response.start",
+                "status": 404,
+                "headers": [[b"content-type", b"text/html"]],
+            }
+        )
+        html = "<h1>500</h1><pre{}></pre>".format(escape(repr(exception)))
+        await send({"type": "http.response.body", "body": html.encode("utf8")})
+
+
+class AsgiView(HTTPMethodView):
+    @classmethod
+    def as_asgi(cls, *class_args, **class_kwargs):
+        async def view(scope, receive, send):
+            # Uses scope to create a Sanic-compatible request object,
+            # then dispatches that to self.get(...) or self.options(...)
+            # along with keyword arguments that were already tucked
+            # into scope["url_route"]["kwargs"] by the router
+            # https://channels.readthedocs.io/en/latest/topics/routing.html#urlrouter
+            path = scope.get("raw_path", scope["path"].encode("utf8"))
+            if scope["query_string"]:
+                path = path + b"?" + scope["query_string"]
+            request = SanicRequest(
+                path,
+                {
+                    "Host": dict(scope.get("headers") or [])
+                    .get(b"host", b"")
+                    .decode("utf8")
+                },
+                "1.1",
+                scope["method"],
+                None,
+            )
+
+            # TODO: Remove need for this
+            class Woo:
+                def get_extra_info(self, key):
+                    return False
+
+            request.app = Woo()
+            request.app.websocket_enabled = False
+            request.transport = Woo()
+            self = view.view_class(*class_args, **class_kwargs)
+            response = await self.dispatch_request(
+                request, **scope["url_route"]["kwargs"]
+            )
+            if hasattr(response, "asgi_send"):
+                await response.asgi_send(send)
+            else:
+                await send(
+                    {
+                        "type": "http.response.start",
+                        "status": response.status,
+                        "headers": [
+                            [key.encode("utf-8"), value.encode("utf-8")]
+                            for key, value in response.headers.items()
+                        ],
+                    }
+                )
+                await send({"type": "http.response.body", "body": response.body})
+
+        view.view_class = cls
+        view.__doc__ = cls.__doc__
+        view.__module__ = cls.__module__
+        view.__name__ = cls.__name__
+        return view
+
+
+class AsgiStream:
+    def __init__(self, stream_fn, status=200, headers=None, content_type="text/plain"):
+        self.stream_fn = stream_fn
+        self.status = status
+        self.headers = headers or {}
+        self.content_type = content_type
+
+    async def asgi_send(self, send):
+        # Remove any existing content-type header
+        headers = dict(
+            [(k, v) for k, v in self.headers.items() if k.lower() != "content-type"]
+        )
+        headers["content-type"] = self.content_type
+        await send(
+            {
+                "type": "http.response.start",
+                "status": self.status,
+                "headers": [
+                    [key.encode("utf-8"), value.encode("utf-8")]
+                    for key, value in headers.items()
+                ],
+            }
+        )
+        w = AsgiWriter(send)
+        await self.stream_fn(w)
+        await send({"type": "http.response.body", "body": b""})
+
+
+class AsgiWriter:
+    def __init__(self, send):
+        self.send = send
+
+    async def write(self, chunk):
+        await self.send(
+            {
+                "type": "http.response.body",
+                "body": chunk.encode("utf8"),
+                "more_body": True,
+            }
+        )
+
+
+async def asgi_send_json(send, info, status=200, headers=None):
+    headers = headers or {}
+    await asgi_send(
+        send,
+        json.dumps(info),
+        status=status,
+        headers=headers,
+        content_type="application/json",
+    )
+
+
+async def asgi_send_html(send, html, status=200, headers=None):
+    headers = headers or {}
+    await asgi_send(
+        send, html, status=status, headers=headers, content_type="text/html"
+    )
+
+
+async def asgi_send(send, content, status, headers, content_type="text/plain"):
+    await asgi_start(send, status, headers, content_type)
+    await send({"type": "http.response.body", "body": content.encode("utf8")})
+
+
+async def asgi_start(send, status, headers, content_type="text/plain"):
+    # Remove any existing content-type header
+    headers = dict([(k, v) for k, v in headers.items() if k.lower() != "content-type"])
+    headers["content-type"] = content_type
+    await send(
+        {
+            "type": "http.response.start",
+            "status": status,
+            "headers": [
+                [key.encode("latin1"), value.encode("latin1")]
+                for key, value in headers.items()
+            ],
+        }
+    )
+
+
+async def asgi_send_file(
+    send, filepath, filename=None, content_type=None, chunk_size=4096
+):
+    headers = {}
+    if filename:
+        headers["Content-Disposition"] = 'attachment; filename="{}"'.format(filename)
+    first = True
+    async with aiofiles.open(filepath, mode="rb") as fp:
+        if first:
+            await asgi_start(
+                send,
+                200,
+                headers,
+                content_type or guess_type(str(filepath))[0] or "text/plain",
+            )
+            first = False
+        more_body = True
+        while more_body:
+            chunk = await fp.read(chunk_size)
+            more_body = len(chunk) == chunk_size
+            await send(
+                {"type": "http.response.body", "body": chunk, "more_body": more_body}
+            )
+
+
+def asgi_static(root_path, chunk_size=4096, headers=None, content_type=None):
+    async def inner_static(scope, receive, send):
+        path = scope["url_route"]["kwargs"]["path"]
+        full_path = (Path(root_path) / path).absolute()
+        # Ensure full_path is within root_path to avoid weird "../" tricks
+        try:
+            full_path.relative_to(root_path)
+        except ValueError:
+            await asgi_send_html(send, "404", 404)
+            return
+        first = True
+        try:
+            await asgi_send_file(send, full_path, chunk_size=chunk_size)
+        except FileNotFoundError:
+            await asgi_send_html(send, "404", 404)
+            return
+
+    return inner_static
+
+
+class AsgiFileDownload:
+    def __init__(
+        self, filepath, filename=None, content_type="application/octet-stream"
+    ):
+        self.filepath = filepath
+        self.filename = filename
+        self.content_type = content_type
+
+    async def asgi_send(self, send):
+        return await asgi_send_file(send, self.filepath, content_type=self.content_type)
diff --git a/datasette/views/base.py b/datasette/views/base.py
index 0b02a13b..a2d6571f 100644
--- a/datasette/views/base.py
+++ b/datasette/views/base.py
@@ -9,7 +9,6 @@ import jinja2
 import pint
 from sanic import response
 from sanic.exceptions import NotFound
-from sanic.views import HTTPMethodView
 from sanic.request import Request as SanicRequest
 
 from html import escape
@@ -29,6 +28,7 @@ from datasette.utils import (
     sqlite3,
     to_css_class,
 )
+from datasette.utils.asgi import AsgiStream, AsgiWriter, AsgiRouter, AsgiView
 
 ureg = pint.UnitRegistry()
 
@@ -52,147 +52,6 @@ class DatasetteError(Exception):
         self.messagge_is_html = messagge_is_html
 
 
-class AsgiRouter:
-    def __init__(self, routes=None):
-        routes = routes or []
-        self.routes = [
-            # Compile any strings to regular expressions
-            ((re.compile(pattern) if isinstance(pattern, str) else pattern), view)
-            for pattern, view in routes
-        ]
-
-    async def __call__(self, scope, receive, send):
-        for regex, view in self.routes:
-            match = regex.match(scope["path"])
-            if match is not None:
-                new_scope = dict(scope, url_route={"kwargs": match.groupdict()})
-                try:
-                    return await view(new_scope, receive, send)
-                except Exception as exception:
-                    return await self.handle_500(scope, receive, send, exception)
-        return await self.handle_404(scope, receive, send)
-
-    async def handle_404(self, scope, receive, send):
-        await send(
-            {
-                "type": "http.response.start",
-                "status": 404,
-                "headers": [[b"content-type", b"text/html"]],
-            }
-        )
-        await send({"type": "http.response.body", "body": b"<h1>404</h1>"})
-
-    async def handle_500(self, scope, receive, send, exception):
-        await send(
-            {
-                "type": "http.response.start",
-                "status": 404,
-                "headers": [[b"content-type", b"text/html"]],
-            }
-        )
-        html = "<h1>500</h1><pre{}></pre>".format(escape(repr(exception)))
-        await send({"type": "http.response.body", "body": html.encode("utf8")})
-
-
-class AsgiView(HTTPMethodView):
-    @classmethod
-    def as_asgi(cls, *class_args, **class_kwargs):
-        async def view(scope, receive, send):
-            # Uses scope to create a Sanic-compatible request object,
-            # then dispatches that to self.get(...) or self.options(...)
-            # along with keyword arguments that were already tucked
-            # into scope["url_route"]["kwargs"] by the router
-            # https://channels.readthedocs.io/en/latest/topics/routing.html#urlrouter
-            path = scope.get("raw_path", scope["path"].encode("utf8"))
-            if scope["query_string"]:
-                path = path + b"?" + scope["query_string"]
-            request = SanicRequest(
-                path,
-                {
-                    "Host": dict(scope.get("headers") or [])
-                    .get(b"host", b"")
-                    .decode("utf8")
-                },
-                "1.1",
-                scope["method"],
-                None,
-            )
-
-            class Woo:
-                def get_extra_info(self, key):
-                    return False
-
-            request.app = Woo()
-            request.app.websocket_enabled = False
-            request.transport = Woo()
-            self = view.view_class(*class_args, **class_kwargs)
-            response = await self.dispatch_request(
-                request, **scope["url_route"]["kwargs"]
-            )
-            if hasattr(response, "asgi_send"):
-                await response.asgi_send(send)
-            else:
-                await send(
-                    {
-                        "type": "http.response.start",
-                        "status": response.status,
-                        "headers": [
-                            [key.encode("utf-8"), value.encode("utf-8")]
-                            for key, value in response.headers.items()
-                        ],
-                    }
-                )
-                await send({"type": "http.response.body", "body": response.body})
-
-        view.view_class = cls
-        view.__doc__ = cls.__doc__
-        view.__module__ = cls.__module__
-        view.__name__ = cls.__name__
-        return view
-
-
-class AsgiStream:
-    def __init__(self, stream_fn, status=200, headers=None, content_type="text/plain"):
-        self.stream_fn = stream_fn
-        self.status = status
-        self.headers = headers or {}
-        self.content_type = content_type
-
-    async def asgi_send(self, send):
-        # Remove any existing content-type header
-        headers = dict(
-            [(k, v) for k, v in self.headers.items() if k.lower() != "content-type"]
-        )
-        headers["content-type"] = self.content_type
-        await send(
-            {
-                "type": "http.response.start",
-                "status": self.status,
-                "headers": [
-                    [key.encode("utf-8"), value.encode("utf-8")]
-                    for key, value in headers.items()
-                ],
-            }
-        )
-        w = AsgiWriter(send)
-        await self.stream_fn(w)
-        await send({"type": "http.response.body", "body": b""})
-
-
-class AsgiWriter:
-    def __init__(self, send):
-        self.send = send
-
-    async def write(self, chunk):
-        await self.send(
-            {
-                "type": "http.response.body",
-                "body": chunk.encode("utf8"),
-                "more_body": True,
-            }
-        )
-
-
 class BaseView(AsgiView):
     ds = None
 
diff --git a/datasette/views/database.py b/datasette/views/database.py
index a5b606f1..4809fef0 100644
--- a/datasette/views/database.py
+++ b/datasette/views/database.py
@@ -3,8 +3,9 @@ import os
 from sanic import response
 
 from datasette.utils import to_css_class, validate_sql_select
+from datasette.utils.asgi import AsgiFileDownload
 
-from .base import DataView, DatasetteError
+from .base import DatasetteError, DataView
 
 
 class DatabaseView(DataView):
@@ -79,8 +80,8 @@ class DatabaseDownload(DataView):
         if not db.path:
             raise DatasetteError("Cannot download database", status=404)
         filepath = db.path
-        return await response.file_stream(
+        return AsgiFileDownload(
             filepath,
             filename=os.path.basename(filepath),
-            mime_type="application/octet-stream",
+            content_type="application/octet-stream",
         )