diff --git a/src/core/CCByte_buffer.ml b/src/core/CCByte_buffer.ml
new file mode 100644
index 00000000..aa612af6
--- /dev/null
+++ b/src/core/CCByte_buffer.ml
@@ -0,0 +1,114 @@
+type 'a iter = ('a -> unit) -> unit
+
+type t = {
+  mutable bytes: bytes;
+  mutable sz: int;
+}
+
+let create ?(size=0) () : t =
+  let bytes =
+    if size=0 then Bytes.unsafe_of_string "" else Bytes.create size in
+  { sz=size; bytes }
+
+let[@inline] capacity self : int = Bytes.length self.bytes
+let[@inline] bytes self = self.bytes
+let[@inline] length self = self.sz
+
+let[@inline] is_empty self = self.sz = 0
+let[@inline] clear self = self.sz <- 0
+
+let grow_cap_ self =
+  min Sys.max_string_length
+    (let n = capacity self in n + n lsl 1 + 5)
+
+let grow_to_ self newcap =
+  if newcap = capacity self then (
+    invalid_arg "byte_buf: cannot grow further";
+  );
+  let newbytes = Bytes.create newcap in
+  Bytes.blit self.bytes 0 newbytes 0 self.sz;
+  self.bytes <- newbytes
+
+let[@inline never] grow_ self =
+  let newcap = grow_cap_ self in
+  grow_to_ self newcap
+
+let ensure_cap self n =
+  if n>capacity self then (
+    let newcap = max n (grow_cap_ self) in
+    grow_to_ self newcap
+  )
+
+let shrink_to self n =
+  if self.sz > n then self.sz <- n
+
+let append_buf (self:t) buf : unit =
+  let n = Buffer.length buf in
+  ensure_cap self (length self + n);
+  Buffer.blit buf 0 self.bytes self.sz n;
+  self.sz <- self.sz + n
+
+let append_subbytes self b off len =
+  ensure_cap self (length self + len);
+  Bytes.blit b off self.bytes self.sz len;
+  self.sz <- self.sz + len
+
+let append_bytes self b = append_subbytes self b 0 (Bytes.length b)
+let append_string self s = append_bytes self (Bytes.unsafe_of_string s)
+let append_substring self s off len = append_subbytes self (Bytes.unsafe_of_string s) off len
+
+let[@inline] add_char_unsafe_ self c =
+  Bytes.unsafe_set self.bytes self.sz c;
+  self.sz <- self.sz + 1
+
+let[@inline] add_char self c =
+  if self.sz = capacity self then grow_ self;
+  add_char_unsafe_ self c
+
+let[@inline] unsafe_get self i = Bytes.unsafe_get self.bytes i
+let[@inline] unsafe_set self i c = Bytes.unsafe_set self.bytes i c
+
+let[@inline] get self i =
+  if i < 0 || i >= self.sz then invalid_arg "Byte_buf.get";
+  unsafe_get self i
+
+let[@inline] set self i c =
+  if i < 0 || i >= self.sz then invalid_arg "Byte_buf.set";
+  unsafe_set self i c
+
+let[@inline] append_iter self i = i (add_char self)
+let[@inline] append_seq self seq = Seq.iter (add_char self) seq
+
+let fold_left f acc self =
+  let {bytes; sz} = self in (* capture current content *)
+
+  let acc = ref acc in
+  for i=0 to sz do
+    acc := f !acc (Bytes.unsafe_get bytes i)
+  done;
+  !acc
+
+let iter f self =
+  let {bytes; sz} = self in (* capture current content *)
+  for i=0 to sz do
+    f (Bytes.unsafe_get bytes i)
+  done
+
+let of_seq seq =
+  let self = create ~size:32 () in
+  append_seq self seq;
+  self
+
+let of_iter iter =
+  let self = create ~size:32 () in
+  append_iter self iter;
+  self
+
+let to_iter self yield = iter yield self
+let to_seq self =
+  let {bytes;sz} = self in
+  let rec s i () =
+    if i= sz then Seq.Nil
+    else Seq.Cons (Bytes.unsafe_get bytes i, s (i+1))
+  in
+  s 0
diff --git a/src/core/CCByte_buffer.mli b/src/core/CCByte_buffer.mli
new file mode 100644
index 00000000..9592094d
--- /dev/null
+++ b/src/core/CCByte_buffer.mli
@@ -0,0 +1,66 @@
+
+(** Byte buffer.
+
+    A dynamic vector of bytes.
+    @since NEXT_RELEASE
+*)
+
+type t
+
+type 'a iter = ('a -> unit) -> unit
+
+val create : ?size:int -> unit -> t
+
+val length : t -> int
+(** Current length. *)
+
+val capacity : t -> int
+(** Current capacity (size of the array returned by {!bytes}) *)
+
+val bytes : t -> bytes
+(** Access the underlying byte buffer. This buffer can change after
+    operations that affect the capacity (e.g. {!add_char}). *)
+
+val clear : t -> unit
+
+val ensure_cap : t -> int -> unit
+(** [ensure_cap self n] ensures that [capacity self >= n]. *)
+
+val shrink_to : t -> int -> unit
+(** [shrink_to buf n] reduces [length buf] to at most [n].
+    Does nothing if the length is already <= n. *)
+
+val add_char : t -> char -> unit
+(** Push a character at the end. *)
+
+val append_bytes : t -> bytes -> unit
+
+val append_subbytes : t -> bytes -> int -> int -> unit
+
+val append_string : t -> string -> unit
+
+val append_substring : t -> string -> int -> int -> unit
+
+val append_buf : t -> Buffer.t -> unit
+
+val append_iter : t -> char iter -> unit
+
+val append_seq : t -> char Seq.t -> unit
+
+val get : t -> int -> char
+
+val unsafe_get : t -> int -> char
+
+val set : t -> int -> char -> unit
+
+val unsafe_set : t -> int -> char -> unit
+
+val iter : (char -> unit) -> t -> unit
+
+val fold_left : ('a -> char -> 'a) -> 'a -> t -> 'a
+
+val of_iter : char iter -> t
+val of_seq : char Seq.t -> t
+
+val to_iter : t -> char iter
+val to_seq : t -> char Seq.t
diff --git a/src/core/containers.ml b/src/core/containers.ml
index c6172f92..3d7951e2 100644
--- a/src/core/containers.ml
+++ b/src/core/containers.ml
@@ -5,6 +5,7 @@
 
 module Array = CCArray
 module Bool = CCBool
+module Byte_buf = CCByte_buf
 module Char = CCChar
 module Equal = CCEqual
 module Either = CCEither
diff --git a/src/core/containersLabels.ml b/src/core/containersLabels.ml
index 29b1e21a..a320761f 100644
--- a/src/core/containersLabels.ml
+++ b/src/core/containersLabels.ml
@@ -5,6 +5,7 @@
 
 module Array = CCArrayLabels
 module Bool = CCBool
+module Byte_buf = CCByte_buf
 module Char = CCChar
 module Equal = CCEqualLabels
 module Either = CCEither