diff --git a/docs/reference/types.rst b/docs/reference/types.rst
index d249b9294..f39e1c2b7 100644
--- a/docs/reference/types.rst
+++ b/docs/reference/types.rst
@@ -5,6 +5,10 @@ Types
 
 .. autodata:: Data
 
+.. autodata:: BytesLike
+
+.. autodata:: DataLike
+
 .. autodata:: LoggerLike
 
 .. autodata:: StatusLike
diff --git a/src/websockets/asyncio/connection.py b/src/websockets/asyncio/connection.py
index 6acced0c1..a13757075 100644
--- a/src/websockets/asyncio/connection.py
+++ b/src/websockets/asyncio/connection.py
@@ -19,10 +19,10 @@
     ConnectionClosedOK,
     ProtocolError,
 )
-from ..frames import DATA_OPCODES, BytesLike, CloseCode, Frame, Opcode
+from ..frames import DATA_OPCODES, CloseCode, Frame, Opcode
 from ..http11 import Request, Response
 from ..protocol import CLOSED, OPEN, Event, Protocol, State
-from ..typing import Data, LoggerLike, Subprotocol
+from ..typing import BytesLike, Data, DataLike, LoggerLike, Subprotocol
 from .compatibility import (
     TimeoutError,
     aiter,
@@ -402,7 +402,7 @@ async def recv_streaming(self, decode: bool | None = None) -> AsyncIterator[Data
 
     async def send(
         self,
-        message: Data | Iterable[Data] | AsyncIterable[Data],
+        message: DataLike | Iterable[DataLike] | AsyncIterable[DataLike],
         text: bool | None = None,
     ) -> None:
         """
@@ -657,7 +657,7 @@ async def wait_closed(self) -> None:
         """
         await asyncio.shield(self.connection_lost_waiter)
 
-    async def ping(self, data: Data | None = None) -> Awaitable[float]:
+    async def ping(self, data: DataLike | None = None) -> Awaitable[float]:
         """
         Send a Ping_.
 
@@ -710,7 +710,7 @@ async def ping(self, data: Data | None = None) -> Awaitable[float]:
             self.protocol.send_ping(data)
             return pong_waiter
 
-    async def pong(self, data: Data = b"") -> None:
+    async def pong(self, data: DataLike = b"") -> None:
         """
         Send a Pong_.
 
@@ -1134,7 +1134,7 @@ def eof_received(self) -> None:
 
 def broadcast(
     connections: Iterable[Connection],
-    message: Data,
+    message: DataLike,
     raise_exceptions: bool = False,
 ) -> None:
     """
diff --git a/src/websockets/asyncio/messages.py b/src/websockets/asyncio/messages.py
index 1fd41811c..af26d5d7a 100644
--- a/src/websockets/asyncio/messages.py
+++ b/src/websockets/asyncio/messages.py
@@ -179,6 +179,7 @@ async def get(self, decode: bool | None = None) -> Data:
         finally:
             self.get_in_progress = False
 
+        # This converts frame.data to bytes when it's a bytearray.
         data = b"".join(frame.data for frame in frames)
         if decode:
             return data.decode()
@@ -243,7 +244,8 @@ async def get_iter(self, decode: bool | None = None) -> AsyncIterator[Data]:
             decoder = UTF8Decoder()
             yield decoder.decode(frame.data, frame.fin)
         else:
-            yield frame.data
+            # Convert to bytes when frame.data is a bytearray.
+            yield bytes(frame.data)
 
         # Following frames, for fragmented messages
         while not frame.fin:
@@ -257,7 +259,8 @@ async def get_iter(self, decode: bool | None = None) -> AsyncIterator[Data]:
             if decode:
                 yield decoder.decode(frame.data, frame.fin)
             else:
-                yield frame.data
+                # Convert to bytes when frame.data is a bytearray.
+                yield bytes(frame.data)
 
         self.get_in_progress = False
 
diff --git a/src/websockets/extensions/permessage_deflate.py b/src/websockets/extensions/permessage_deflate.py
index 7e9e7a5dd..2bc63d799 100644
--- a/src/websockets/extensions/permessage_deflate.py
+++ b/src/websockets/extensions/permessage_deflate.py
@@ -13,7 +13,7 @@
     PayloadTooBig,
     ProtocolError,
 )
-from ..typing import ExtensionName, ExtensionParameter
+from ..typing import BytesLike, ExtensionName, ExtensionParameter
 from .base import ClientExtensionFactory, Extension, ServerExtensionFactory
 
 
@@ -129,6 +129,7 @@ def decode(
         # Uncompress data. Protect against zip bombs by preventing zlib from
         # decompressing more than max_length bytes (except when the limit is
         # disabled with max_size = None).
+        data: BytesLike
         if frame.fin and len(frame.data) < 2044:
             # Profiling shows that appending four bytes, which makes a copy, is
             # faster than calling decompress() again when data is less than 2kB.
@@ -182,6 +183,7 @@ def encode(self, frame: frames.Frame) -> frames.Frame:
                 )
 
         # Compress data.
+        data: BytesLike
         data = self.encoder.compress(frame.data) + self.encoder.flush(zlib.Z_SYNC_FLUSH)
         if frame.fin:
             # Sync flush generates between 5 or 6 bytes, ending with the bytes
diff --git a/src/websockets/frames.py b/src/websockets/frames.py
index 3a7077b66..89c48f390 100644
--- a/src/websockets/frames.py
+++ b/src/websockets/frames.py
@@ -10,6 +10,7 @@
 from typing import Callable
 
 from .exceptions import PayloadTooBig, ProtocolError
+from .typing import BytesLike
 
 
 try:
@@ -118,9 +119,6 @@ class CloseCode(enum.IntEnum):
 }
 
 
-BytesLike = bytes, bytearray, memoryview
-
-
 @dataclasses.dataclass
 class Frame:
     """
@@ -140,7 +138,7 @@ class Frame:
     """
 
     opcode: Opcode
-    data: bytes | bytearray | memoryview
+    data: BytesLike
     fin: bool = True
     rsv1: bool = False
     rsv2: bool = False
@@ -202,7 +200,7 @@ def __str__(self) -> str:
     @classmethod
     def parse(
         cls,
-        read_exact: Callable[[int], Generator[None, None, bytes]],
+        read_exact: Callable[[int], Generator[None, None, bytes | bytearray]],
         *,
         mask: bool,
         max_size: int | None = None,
@@ -324,6 +322,7 @@ def serialize(
             output.write(mask_bytes)
 
         # Prepare the data.
+        data: BytesLike
         if mask:
             data = apply_mask(self.data, mask_bytes)
         else:
@@ -383,7 +382,7 @@ def __str__(self) -> str:
         return result
 
     @classmethod
-    def parse(cls, data: bytes) -> Close:
+    def parse(cls, data: BytesLike) -> Close:
         """
         Parse the payload of a close frame.
 
@@ -395,6 +394,8 @@ def parse(cls, data: bytes) -> Close:
             UnicodeDecodeError: If the reason isn't valid UTF-8.
 
         """
+        if isinstance(data, memoryview):
+            raise AssertionError("only compressed outgoing frames use memoryview")
         if len(data) >= 2:
             (code,) = struct.unpack("!H", data[:2])
             reason = data[2:].decode()
diff --git a/src/websockets/http11.py b/src/websockets/http11.py
index 290ef087e..5af73eb0c 100644
--- a/src/websockets/http11.py
+++ b/src/websockets/http11.py
@@ -47,7 +47,7 @@
 MAX_BODY_SIZE = int(os.environ.get("WEBSOCKETS_MAX_BODY_SIZE", "1_048_576"))  # 1 MiB
 
 
-def d(value: bytes) -> str:
+def d(value: bytes | bytearray) -> str:
     """
     Decode a bytestring for interpolating into an error message.
 
@@ -102,7 +102,7 @@ def exception(self) -> Exception | None:  # pragma: no cover
     @classmethod
     def parse(
         cls,
-        read_line: Callable[[int], Generator[None, None, bytes]],
+        read_line: Callable[[int], Generator[None, None, bytes | bytearray]],
     ) -> Generator[None, None, Request]:
         """
         Parse a WebSocket handshake request.
@@ -194,7 +194,7 @@ class Response:
     status_code: int
     reason_phrase: str
     headers: Headers
-    body: bytes = b""
+    body: bytes | bytearray = b""
 
     _exception: Exception | None = None
 
@@ -210,9 +210,9 @@ def exception(self) -> Exception | None:  # pragma: no cover
     @classmethod
     def parse(
         cls,
-        read_line: Callable[[int], Generator[None, None, bytes]],
-        read_exact: Callable[[int], Generator[None, None, bytes]],
-        read_to_eof: Callable[[int], Generator[None, None, bytes]],
+        read_line: Callable[[int], Generator[None, None, bytes | bytearray]],
+        read_exact: Callable[[int], Generator[None, None, bytes | bytearray]],
+        read_to_eof: Callable[[int], Generator[None, None, bytes | bytearray]],
         proxy: bool = False,
     ) -> Generator[None, None, Response]:
         """
@@ -276,6 +276,7 @@ def parse(
 
         headers = yield from parse_headers(read_line)
 
+        body: bytes | bytearray
         if proxy:
             body = b""
         else:
@@ -299,8 +300,8 @@ def serialize(self) -> bytes:
 
 
 def parse_line(
-    read_line: Callable[[int], Generator[None, None, bytes]],
-) -> Generator[None, None, bytes]:
+    read_line: Callable[[int], Generator[None, None, bytes | bytearray]],
+) -> Generator[None, None, bytes | bytearray]:
     """
     Parse a single line.
 
@@ -326,7 +327,7 @@ def parse_line(
 
 
 def parse_headers(
-    read_line: Callable[[int], Generator[None, None, bytes]],
+    read_line: Callable[[int], Generator[None, None, bytes | bytearray]],
 ) -> Generator[None, None, Headers]:
     """
     Parse HTTP headers.
@@ -379,10 +380,10 @@ def parse_headers(
 def read_body(
     status_code: int,
     headers: Headers,
-    read_line: Callable[[int], Generator[None, None, bytes]],
-    read_exact: Callable[[int], Generator[None, None, bytes]],
-    read_to_eof: Callable[[int], Generator[None, None, bytes]],
-) -> Generator[None, None, bytes]:
+    read_line: Callable[[int], Generator[None, None, bytes | bytearray]],
+    read_exact: Callable[[int], Generator[None, None, bytes | bytearray]],
+    read_to_eof: Callable[[int], Generator[None, None, bytes | bytearray]],
+) -> Generator[None, None, bytes | bytearray]:
     # https://datatracker.ietf.org/doc/html/rfc7230#section-3.3.3
 
     # Since websockets only does GET requests (no HEAD, no CONNECT), all
diff --git a/src/websockets/legacy/framing.py b/src/websockets/legacy/framing.py
index add0c6e0e..452d2fb34 100644
--- a/src/websockets/legacy/framing.py
+++ b/src/websockets/legacy/framing.py
@@ -6,8 +6,7 @@
 
 from .. import extensions, frames
 from ..exceptions import PayloadTooBig, ProtocolError
-from ..frames import BytesLike
-from ..typing import Data
+from ..typing import BytesLike, DataLike
 
 
 try:
@@ -19,7 +18,7 @@
 class Frame(NamedTuple):
     fin: bool
     opcode: frames.Opcode
-    data: bytes
+    data: BytesLike
     rsv1: bool = False
     rsv2: bool = False
     rsv3: bool = False
@@ -147,7 +146,7 @@ def write(
         write(self.new_frame.serialize(mask=mask, extensions=extensions))
 
 
-def prepare_data(data: Data) -> tuple[int, bytes]:
+def prepare_data(data: DataLike) -> tuple[int, BytesLike]:
     """
     Convert a string or byte-like object to an opcode and a bytes-like object.
 
@@ -171,7 +170,7 @@ def prepare_data(data: Data) -> tuple[int, bytes]:
         raise TypeError("data must be str or bytes-like")
 
 
-def prepare_ctrl(data: Data) -> bytes:
+def prepare_ctrl(data: DataLike) -> bytes:
     """
     Convert a string or byte-like object to bytes.
 
diff --git a/src/websockets/legacy/protocol.py b/src/websockets/legacy/protocol.py
index 1d604677a..03de30124 100644
--- a/src/websockets/legacy/protocol.py
+++ b/src/websockets/legacy/protocol.py
@@ -39,7 +39,7 @@
     Opcode,
 )
 from ..protocol import State
-from ..typing import Data, LoggerLike, Subprotocol
+from ..typing import BytesLike, Data, DataLike, LoggerLike, Subprotocol
 from .framing import Frame, prepare_ctrl, prepare_data
 
 
@@ -563,7 +563,7 @@ async def recv(self) -> Data:
 
     async def send(
         self,
-        message: Data | Iterable[Data] | AsyncIterable[Data],
+        message: DataLike | Iterable[DataLike] | AsyncIterable[DataLike],
     ) -> None:
         """
         Send a message.
@@ -638,7 +638,7 @@ async def send(
 
         elif isinstance(message, Iterable):
             # Work around https://github.com/python/mypy/issues/6227
-            message = cast(Iterable[Data], message)
+            message = cast(Iterable[DataLike], message)
 
             iter_message = iter(message)
             try:
@@ -678,14 +678,14 @@ async def send(
             # Implement aiter_message = aiter(message) without aiter
             # Work around https://github.com/python/mypy/issues/5738
             aiter_message = cast(
-                Callable[[AsyncIterable[Data]], AsyncIterator[Data]],
+                Callable[[AsyncIterable[DataLike]], AsyncIterator[DataLike]],
                 type(message).__aiter__,
             )(message)
             try:
                 # Implement fragment = anext(aiter_message) without anext
                 # Work around https://github.com/python/mypy/issues/5738
                 fragment = await cast(
-                    Callable[[AsyncIterator[Data]], Awaitable[Data]],
+                    Callable[[AsyncIterator[DataLike]], Awaitable[DataLike]],
                     type(aiter_message).__anext__,
                 )(aiter_message)
             except StopAsyncIteration:
@@ -788,7 +788,7 @@ async def wait_closed(self) -> None:
         """
         await asyncio.shield(self.connection_lost_waiter)
 
-    async def ping(self, data: Data | None = None) -> Awaitable[float]:
+    async def ping(self, data: DataLike | None = None) -> Awaitable[float]:
         """
         Send a Ping_.
 
@@ -847,7 +847,7 @@ async def ping(self, data: Data | None = None) -> Awaitable[float]:
 
         return asyncio.shield(pong_waiter)
 
-    async def pong(self, data: Data = b"") -> None:
+    async def pong(self, data: DataLike = b"") -> None:
         """
         Send a Pong_.
 
@@ -1025,10 +1025,12 @@ async def read_message(self) -> Data | None:
 
         # Shortcut for the common case - no fragmentation
         if frame.fin:
-            return frame.data.decode() if text else frame.data
+            if isinstance(frame.data, memoryview):
+                raise AssertionError("only compressed outgoing frames use memoryview")
+            return frame.data.decode() if text else bytes(frame.data)
 
         # 5.4. Fragmentation
-        fragments: list[Data] = []
+        fragments: list[DataLike] = []
         max_size = self.max_size
         if text:
             decoder_factory = codecs.getincrementaldecoder("utf-8")
@@ -1152,7 +1154,7 @@ async def read_frame(self, max_size: int | None) -> Frame:
             self.logger.debug("< %s", frame)
         return frame
 
-    def write_frame_sync(self, fin: bool, opcode: int, data: bytes) -> None:
+    def write_frame_sync(self, fin: bool, opcode: int, data: BytesLike) -> None:
         frame = Frame(fin, Opcode(opcode), data)
         if self.debug:
             self.logger.debug("> %s", frame)
@@ -1174,7 +1176,7 @@ async def drain(self) -> None:
             await self.ensure_open()
 
     async def write_frame(
-        self, fin: bool, opcode: int, data: bytes, *, _state: int = State.OPEN
+        self, fin: bool, opcode: int, data: BytesLike, *, _state: int = State.OPEN
     ) -> None:
         # Defensive assertion for protocol compliance.
         if self.state is not _state:  # pragma: no cover
@@ -1184,7 +1186,9 @@ async def write_frame(
         self.write_frame_sync(fin, opcode, data)
         await self.drain()
 
-    async def write_close_frame(self, close: Close, data: bytes | None = None) -> None:
+    async def write_close_frame(
+        self, close: Close, data: BytesLike | None = None
+    ) -> None:
         """
         Write a close frame if and only if the connection state is OPEN.
 
@@ -1538,7 +1542,7 @@ def eof_received(self) -> None:
 
 def broadcast(
     websockets: Iterable[WebSocketCommonProtocol],
-    message: Data,
+    message: DataLike,
     raise_exceptions: bool = False,
 ) -> None:
     """
diff --git a/src/websockets/protocol.py b/src/websockets/protocol.py
index 4054941b9..bf05eb546 100644
--- a/src/websockets/protocol.py
+++ b/src/websockets/protocol.py
@@ -28,7 +28,7 @@
 )
 from .http11 import Request, Response
 from .streams import StreamReader
-from .typing import LoggerLike, Origin, Subprotocol
+from .typing import BytesLike, LoggerLike, Origin, Subprotocol
 
 
 __all__ = [
@@ -291,7 +291,7 @@ def receive_eof(self) -> None:
 
     # Public methods for sending events.
 
-    def send_continuation(self, data: bytes, fin: bool) -> None:
+    def send_continuation(self, data: BytesLike, fin: bool) -> None:
         """
         Send a `Continuation frame`_.
 
@@ -315,7 +315,7 @@ def send_continuation(self, data: bytes, fin: bool) -> None:
         self.expect_continuation_frame = not fin
         self.send_frame(Frame(OP_CONT, data, fin))
 
-    def send_text(self, data: bytes, fin: bool = True) -> None:
+    def send_text(self, data: BytesLike, fin: bool = True) -> None:
         """
         Send a `Text frame`_.
 
@@ -338,7 +338,7 @@ def send_text(self, data: bytes, fin: bool = True) -> None:
         self.expect_continuation_frame = not fin
         self.send_frame(Frame(OP_TEXT, data, fin))
 
-    def send_binary(self, data: bytes, fin: bool = True) -> None:
+    def send_binary(self, data: BytesLike, fin: bool = True) -> None:
         """
         Send a `Binary frame`_.
 
@@ -397,7 +397,7 @@ def send_close(self, code: int | None = None, reason: str = "") -> None:
         self.close_sent = close
         self.state = CLOSING
 
-    def send_ping(self, data: bytes) -> None:
+    def send_ping(self, data: BytesLike) -> None:
         """
         Send a `Ping frame`_.
 
@@ -413,7 +413,7 @@ def send_ping(self, data: bytes) -> None:
             raise InvalidState(f"connection is {self.state.name.lower()}")
         self.send_frame(Frame(OP_PING, data))
 
-    def send_pong(self, data: bytes) -> None:
+    def send_pong(self, data: BytesLike) -> None:
         """
         Send a `Pong frame`_.
 
diff --git a/src/websockets/speedups.pyi b/src/websockets/speedups.pyi
index 821438a06..ffd6c3e07 100644
--- a/src/websockets/speedups.pyi
+++ b/src/websockets/speedups.pyi
@@ -1 +1,3 @@
-def apply_mask(data: bytes, mask: bytes) -> bytes: ...
+from .typing import BytesLike
+
+def apply_mask(data: BytesLike, mask: bytes | bytearray) -> bytes: ...
diff --git a/src/websockets/streams.py b/src/websockets/streams.py
index f52e6193a..08ff58e77 100644
--- a/src/websockets/streams.py
+++ b/src/websockets/streams.py
@@ -17,7 +17,7 @@ def __init__(self) -> None:
         self.buffer = bytearray()
         self.eof = False
 
-    def read_line(self, m: int) -> Generator[None, None, bytes]:
+    def read_line(self, m: int) -> Generator[None, None, bytearray]:
         """
         Read a LF-terminated line from the stream.
 
@@ -51,7 +51,7 @@ def read_line(self, m: int) -> Generator[None, None, bytes]:
         del self.buffer[:n]
         return r
 
-    def read_exact(self, n: int) -> Generator[None, None, bytes]:
+    def read_exact(self, n: int) -> Generator[None, None, bytearray]:
         """
         Read a given number of bytes from the stream.
 
@@ -74,7 +74,7 @@ def read_exact(self, n: int) -> Generator[None, None, bytes]:
         del self.buffer[:n]
         return r
 
-    def read_to_eof(self, m: int) -> Generator[None, None, bytes]:
+    def read_to_eof(self, m: int) -> Generator[None, None, bytearray]:
         """
         Read all bytes from the stream.
 
diff --git a/src/websockets/sync/client.py b/src/websockets/sync/client.py
index bfaef61eb..98860deee 100644
--- a/src/websockets/sync/client.py
+++ b/src/websockets/sync/client.py
@@ -16,7 +16,7 @@
 from ..http11 import USER_AGENT, Response
 from ..protocol import CONNECTING, Event
 from ..streams import StreamReader
-from ..typing import LoggerLike, Origin, Subprotocol
+from ..typing import BytesLike, LoggerLike, Origin, Subprotocol
 from ..uri import Proxy, WebSocketURI, get_proxy, parse_proxy, parse_uri
 from .connection import Connection
 from .utils import Deadline
@@ -633,10 +633,10 @@ def recv(self, buflen: int) -> bytes:
         except ssl_module.SSLEOFError:
             return b""  # always ignore ragged EOFs
 
-    def send(self, data: bytes) -> int:
+    def send(self, data: BytesLike) -> int:
         return self.run_io(self.ssl_object.write, data)
 
-    def sendall(self, data: bytes) -> None:
+    def sendall(self, data: BytesLike) -> None:
         # adapted from ssl_module.SSLSocket.sendall()
         count = 0
         with memoryview(data) as view, view.cast("B") as byte_view:
diff --git a/src/websockets/sync/connection.py b/src/websockets/sync/connection.py
index bedbf4def..d8b23a8a0 100644
--- a/src/websockets/sync/connection.py
+++ b/src/websockets/sync/connection.py
@@ -18,10 +18,10 @@
     ConnectionClosedOK,
     ProtocolError,
 )
-from ..frames import DATA_OPCODES, BytesLike, CloseCode, Frame, Opcode
+from ..frames import DATA_OPCODES, CloseCode, Frame, Opcode
 from ..http11 import Request, Response
 from ..protocol import CLOSED, OPEN, Event, Protocol, State
-from ..typing import Data, LoggerLike, Subprotocol
+from ..typing import BytesLike, Data, DataLike, LoggerLike, Subprotocol
 from .messages import Assembler
 from .utils import Deadline
 
@@ -410,7 +410,7 @@ def recv_streaming(self, decode: bool | None = None) -> Iterator[Data]:
 
     def send(
         self,
-        message: Data | Iterable[Data],
+        message: DataLike | Iterable[DataLike],
         text: bool | None = None,
     ) -> None:
         """
@@ -602,7 +602,7 @@ def close(self, code: int = CloseCode.NORMAL_CLOSURE, reason: str = "") -> None:
 
     def ping(
         self,
-        data: Data | None = None,
+        data: DataLike | None = None,
         ack_on_close: bool = False,
     ) -> threading.Event:
         """
@@ -659,7 +659,7 @@ def ping(
             self.protocol.send_ping(data)
             return pong_waiter
 
-    def pong(self, data: Data = b"") -> None:
+    def pong(self, data: DataLike = b"") -> None:
         """
         Send a Pong_.
 
diff --git a/src/websockets/sync/messages.py b/src/websockets/sync/messages.py
index c619e78a1..c4d04bc83 100644
--- a/src/websockets/sync/messages.py
+++ b/src/websockets/sync/messages.py
@@ -193,6 +193,7 @@ def get(self, timeout: float | None = None, decode: bool | None = None) -> Data:
         finally:
             self.get_in_progress = False
 
+        # This converts frame.data to bytes when it's a bytearray.
         data = b"".join(frame.data for frame in frames)
         if decode:
             return data.decode()
@@ -255,7 +256,8 @@ def get_iter(self, decode: bool | None = None) -> Iterator[Data]:
             decoder = UTF8Decoder()
             yield decoder.decode(frame.data, frame.fin)
         else:
-            yield frame.data
+            # Convert to bytes when frame.data is a bytearray.
+            yield bytes(frame.data)
 
         # Following frames, for fragmented messages
         while not frame.fin:
@@ -266,7 +268,8 @@ def get_iter(self, decode: bool | None = None) -> Iterator[Data]:
             if decode:
                 yield decoder.decode(frame.data, frame.fin)
             else:
-                yield frame.data
+                # Convert to bytes when frame.data is a bytearray.
+                yield bytes(frame.data)
 
         self.get_in_progress = False
 
diff --git a/src/websockets/typing.py b/src/websockets/typing.py
index 93636e1c9..69b1a8d37 100644
--- a/src/websockets/typing.py
+++ b/src/websockets/typing.py
@@ -20,13 +20,18 @@
 
 Data = str | bytes
 """Types supported in a WebSocket message:
-:class:`str` for a Text_ frame, :class:`bytes` for a Binary_.
+:class:`str` for a Text_ frame, :class:`bytes` for a Binary_ frame.
 
 .. _Text: https://datatracker.ietf.org/doc/html/rfc6455#section-5.6
 .. _Binary : https://datatracker.ietf.org/doc/html/rfc6455#section-5.6
 
 """
 
+BytesLike = bytes | bytearray | memoryview
+"""Types accepted where :class:`bytes` is expected."""
+
+DataLike = str | bytes | bytearray | memoryview
+"""Types accepted where :class:`Data` is expected."""
 
 if TYPE_CHECKING:
     LoggerLike = logging.Logger | logging.LoggerAdapter[Any]
diff --git a/src/websockets/utils.py b/src/websockets/utils.py
index 62d2dc177..b2a90e52b 100644
--- a/src/websockets/utils.py
+++ b/src/websockets/utils.py
@@ -5,6 +5,8 @@
 import secrets
 import sys
 
+from .typing import BytesLike
+
 
 __all__ = ["accept_key", "apply_mask"]
 
@@ -33,7 +35,7 @@ def accept_key(key: str) -> str:
     return base64.b64encode(sha1).decode()
 
 
-def apply_mask(data: bytes, mask: bytes) -> bytes:
+def apply_mask(data: BytesLike, mask: bytes | bytearray) -> bytes:
     """
     Apply masking to the data of a WebSocket message.
 
diff --git a/tox.ini b/tox.ini
index aa88b0591..ce4572e59 100644
--- a/tox.ini
+++ b/tox.ini
@@ -46,6 +46,6 @@ deps =
 commands =
     mypy --strict src
 deps =
-    mypy<1.16.0
+    mypy
     python-socks
     werkzeug