diff --git a/bin/dune b/bin/dune
index 3c6532c2..adb396ec 100644
--- a/bin/dune
+++ b/bin/dune
@@ -1,5 +1,6 @@
 (executable
  (name ydump)
  (public_name ydump)
+ (package yojson)
  (flags (-safe-string))
  (libraries yojson))
diff --git a/bin/ydump.ml b/bin/ydump.ml
index 0565456e..613f18fa 100644
--- a/bin/ydump.ml
+++ b/bin/ydump.ml
@@ -81,7 +81,7 @@ let cat sort output_biniou std compact streaming in_file out_file =
 
   else
     let write_one oc x =
-      output_string oc (Bi_io.string_of_tree (Yojson_biniou.biniou_of_json x))
+      output_string oc (Yojson.Safe.to_string x)
     in
     polycat write_one streaming in_file out_file
 
diff --git a/lib/common.ml b/lib/common.ml
index 935b2c8b..df94ac11 100644
--- a/lib/common.ml
+++ b/lib/common.ml
@@ -19,7 +19,7 @@ let create_in_param ?(len = 256) () = {
 
 
 let utf8_of_code buf x =
-  let add = Bi_outbuf.add_char in
+  let add = Buffer.add_char in
 
   (* Straight <= doesn't work with signed 31-bit ints *)
   let maxbits n x = x lsr n = 0 in
@@ -80,7 +80,7 @@ let is_object_or_array x =
 
 
 type lexer_state = {
-  buf : Bi_outbuf.t;
+  buf : Buffer.t;
     (* Buffer used to accumulate substrings *)
 
   mutable lnum : int;
@@ -97,7 +97,7 @@ type lexer_state = {
 module Lexer_state =
 struct
   type t = lexer_state = {
-    buf : Bi_outbuf.t;
+    buf : Buffer.t;
     mutable lnum : int;
     mutable bol : int;
     mutable fname : string option;
@@ -107,7 +107,7 @@ end
 let init_lexer ?buf ?fname ?(lnum = 1) () =
   let buf =
     match buf with
-	None -> Bi_outbuf.create 256
+	None -> Buffer.create 256
       | Some buf -> buf
   in
   {
diff --git a/lib/common.mli b/lib/common.mli
index 415b3630..28e90aec 100644
--- a/lib/common.mli
+++ b/lib/common.mli
@@ -5,7 +5,7 @@ exception Json_error of string
 val json_error : string -> 'a
 
 type lexer_state = {
-  buf : Bi_outbuf.t;
+  buf : Buffer.t;
     (** Buffer used to accumulate substrings *)
 
   mutable lnum : int;
@@ -22,7 +22,7 @@ type lexer_state = {
 module Lexer_state :
 sig
   type t = lexer_state = {
-    buf : Bi_outbuf.t;
+    buf : Buffer.t;
     mutable lnum : int;
     mutable bol : int;
     mutable fname : string option;
@@ -30,7 +30,7 @@ sig
 end
 
 val init_lexer :
-  ?buf: Bi_outbuf.t ->
+  ?buf: Buffer.t ->
   ?fname: string ->
   ?lnum: int ->
   unit -> lexer_state
diff --git a/lib/dune b/lib/dune
index 5eaecea4..6b817071 100644
--- a/lib/dune
+++ b/lib/dune
@@ -33,8 +33,6 @@
 (library
  (name yojson)
  (public_name yojson)
- (modules yojson yojson_biniou)
- (wrapped false)
- (synopsis "JSON parsing and printing (successor of json-wheel)")
- (flags (-safe-string))
- (libraries biniou))
+ (modules yojson)
+ (synopsis "JSON parsing and printing")
+ (flags (-safe-string)))
diff --git a/lib/read.mli b/lib/read.mli
index 31dd1b96..b1c2c9fa 100644
--- a/lib/read.mli
+++ b/lib/read.mli
@@ -12,7 +12,7 @@ exception Finally of exn * exn
 (** Exception describing a failure in both finalizer and parsing. *)
 
 val from_string :
-  ?buf:Bi_outbuf.t ->
+  ?buf:Buffer.t ->
   ?fname:string ->
   ?lnum:int ->
   string -> t
@@ -25,7 +25,7 @@ val from_string :
   *)
 
 val from_channel :
-  ?buf:Bi_outbuf.t ->
+  ?buf:Buffer.t ->
   ?fname:string ->
   ?lnum:int ->
   in_channel -> t
@@ -33,7 +33,7 @@ val from_channel :
       See [from_string] for the meaning of the optional arguments. *)
 
 val from_file :
-  ?buf:Bi_outbuf.t ->
+  ?buf:Buffer.t ->
   ?fname:string ->
   ?lnum:int ->
   string -> t
@@ -42,7 +42,7 @@ val from_file :
 
 
 type lexer_state = Lexer_state.t = {
-  buf : Bi_outbuf.t;
+  buf : Buffer.t;
   mutable lnum : int;
   mutable bol : int;
   mutable fname : string option;
@@ -52,7 +52,7 @@ type lexer_state = Lexer_state.t = {
     *)
 
 val init_lexer :
-  ?buf: Bi_outbuf.t ->
+  ?buf: Buffer.t ->
   ?fname: string ->
   ?lnum: int ->
   unit -> lexer_state
@@ -72,7 +72,7 @@ val from_lexbuf :
       the end of the JSON value and the end of the input. *)
 
 val stream_from_string :
-  ?buf:Bi_outbuf.t ->
+  ?buf:Buffer.t ->
   ?fname:string ->
   ?lnum:int ->
   string -> t Stream.t
@@ -81,7 +81,7 @@ val stream_from_string :
       See [from_string] for the meaning of the optional arguments. *)
 
 val stream_from_channel :
-  ?buf:Bi_outbuf.t ->
+  ?buf:Buffer.t ->
   ?fin:(unit -> unit) ->
   ?fname:string ->
   ?lnum:int ->
@@ -97,7 +97,7 @@ val stream_from_channel :
       See [from_string] for the meaning of the other optional arguments. *)
 
 val stream_from_file :
-  ?buf:Bi_outbuf.t ->
+  ?buf:Buffer.t ->
   ?fname:string ->
   ?lnum:int ->
   string -> t Stream.t
@@ -124,7 +124,7 @@ type json_line = [ `Json of t | `Exn of exn ]
     (** The type of values resulting from a parsing attempt of a JSON value. *)
 
 val linestream_from_channel :
-  ?buf:Bi_outbuf.t ->
+  ?buf:Buffer.t ->
   ?fin:(unit -> unit) ->
   ?fname:string ->
   ?lnum:int ->
@@ -138,7 +138,7 @@ val linestream_from_channel :
       See [from_string] for the meaning of the other optional arguments. *)
 
 val linestream_from_file :
-  ?buf:Bi_outbuf.t ->
+  ?buf:Buffer.t ->
   ?fname:string ->
   ?lnum:int ->
   string -> json_line Stream.t
diff --git a/lib/read.mll b/lib/read.mll
index 5bdaf837..3e7a4d2f 100644
--- a/lib/read.mll
+++ b/lib/read.mll
@@ -27,7 +27,7 @@
 
   (* see description in common.mli *)
   type lexer_state = Lexer_state.t = {
-    buf : Bi_outbuf.t;
+    buf : Buffer.t;
     mutable lnum : int;
     mutable bol : int;
     mutable fname : string option;
@@ -147,7 +147,7 @@
 
   let add_lexeme buf lexbuf =
     let len = lexbuf.lex_curr_pos - lexbuf.lex_start_pos in
-    Bi_outbuf.add_subbytes buf lexbuf.lex_buffer lexbuf.lex_start_pos len
+    Buffer.add_subbytes buf lexbuf.lex_buffer lexbuf.lex_start_pos len
 
   let map_lexeme f lexbuf =
     let len = lexbuf.lex_curr_pos - lexbuf.lex_start_pos in
@@ -211,7 +211,7 @@ rule read_json v = parse
                 }
   | '"'         {
                   #ifdef STRING
-                    Bi_outbuf.clear v.buf;
+                    Buffer.clear v.buf;
                     `String (finish_string v lexbuf)
                   #elif defined STRINGLIT
                     `Stringlit (finish_stringlit v lexbuf)
@@ -308,7 +308,7 @@ rule read_json v = parse
 
 
 and finish_string v = parse
-    '"'           { Bi_outbuf.contents v.buf }
+    '"'           { Buffer.contents v.buf }
   | '\\'          { finish_escaped_char v lexbuf;
                     finish_string v lexbuf }
   | [^ '"' '\\']+ { add_lexeme v.buf lexbuf;
@@ -317,7 +317,7 @@ and finish_string v = parse
 
 and map_string v f = parse
     '"'           { let b = v.buf in
-                    f (Bytes.to_string b.Bi_outbuf.o_s) 0 b.Bi_outbuf.o_len }
+                    f (Buffer.contents b) 0 (Buffer.length b) }
   | '\\'          { finish_escaped_char v lexbuf;
                     map_string v f lexbuf }
   | [^ '"' '\\']+ { add_lexeme v.buf lexbuf;
@@ -327,12 +327,12 @@ and map_string v f = parse
 and finish_escaped_char v = parse
     '"'
   | '\\'
-  | '/' as c { Bi_outbuf.add_char v.buf c }
-  | 'b'  { Bi_outbuf.add_char v.buf '\b' }
-  | 'f'  { Bi_outbuf.add_char v.buf '\012' }
-  | 'n'  { Bi_outbuf.add_char v.buf '\n' }
-  | 'r'  { Bi_outbuf.add_char v.buf '\r' }
-  | 't'  { Bi_outbuf.add_char v.buf '\t' }
+  | '/' as c { Buffer.add_char v.buf c }
+  | 'b'  { Buffer.add_char v.buf '\b' }
+  | 'f'  { Buffer.add_char v.buf '\012' }
+  | 'n'  { Buffer.add_char v.buf '\n' }
+  | 'r'  { Buffer.add_char v.buf '\r' }
+  | 't'  { Buffer.add_char v.buf '\t' }
   | 'u' (hex as a) (hex as b) (hex as c) (hex as d)
          { let x =
              (hex a lsl 12) lor (hex b lsl 8) lor (hex c lsl 4) lor hex d
@@ -398,7 +398,7 @@ and read_comma v = parse
 
 and start_any_variant v = parse
     '<'      { `Edgy_bracket }
-  | '"'      { Bi_outbuf.clear v.buf;
+  | '"'      { Buffer.clear v.buf;
                `Double_quote }
   | '['      { `Square_bracket }
   | _        { long_error "Expected '<', '\"' or '[' but found" v lexbuf }
@@ -454,7 +454,7 @@ and read_int v = parse
                            with Int_overflow ->
                              lexer_error "Int overflow" v lexbuf }
   | '"'                  { (* Support for double-quoted "ints" *)
-                           Bi_outbuf.clear v.buf;
+                           Buffer.clear v.buf;
                            let s = finish_string v lexbuf in
                            try
                              (* Any OCaml-compliant int will pass,
@@ -475,7 +475,7 @@ and read_int32 v = parse
                            with _ ->
                              lexer_error "Int32 overflow" v lexbuf }
   | '"'                  { (* Support for double-quoted "ints" *)
-                           Bi_outbuf.clear v.buf;
+                           Buffer.clear v.buf;
                            let s = finish_string v lexbuf in
                            try
                              (* Any OCaml-compliant int will pass,
@@ -496,7 +496,7 @@ and read_int64 v = parse
                            with _ ->
                              lexer_error "Int32 overflow" v lexbuf }
   | '"'                  { (* Support for double-quoted "ints" *)
-                           Bi_outbuf.clear v.buf;
+                           Buffer.clear v.buf;
                            let s = finish_string v lexbuf in
                            try
                              (* Any OCaml-compliant int will pass,
@@ -517,7 +517,7 @@ and read_number v = parse
   | "Infinity"  { infinity }
   | "-Infinity" { neg_infinity }
   | number      { float_of_string (lexeme lexbuf) }
-  | '"'         { Bi_outbuf.clear v.buf;
+  | '"'         { Buffer.clear v.buf;
                   let s = finish_string v lexbuf in
                   try
                     (* Any OCaml-compliant float will pass,
@@ -539,13 +539,13 @@ and read_number v = parse
   | eof         { custom_error "Unexpected end of input" v lexbuf }
 
 and read_string v = parse
-    '"'      { Bi_outbuf.clear v.buf;
+    '"'      { Buffer.clear v.buf;
                finish_string v lexbuf }
   | _        { long_error "Expected '\"' but found" v lexbuf }
   | eof      { custom_error "Unexpected end of input" v lexbuf }
 
 and read_ident v = parse
-    '"'      { Bi_outbuf.clear v.buf;
+    '"'      { Buffer.clear v.buf;
                finish_string v lexbuf }
   | ident as s
              { s }
@@ -553,7 +553,7 @@ and read_ident v = parse
   | eof      { custom_error "Unexpected end of input" v lexbuf }
 
 and map_ident v f = parse
-    '"'      { Bi_outbuf.clear v.buf;
+    '"'      { Buffer.clear v.buf;
                map_string v f lexbuf }
   | ident
              { map_lexeme f lexbuf }
@@ -871,7 +871,7 @@ and buffer_json v = parse
 
   | '"'         { finish_buffer_stringlit v lexbuf }
   | '{'          { try
-                     Bi_outbuf.add_char v.buf '{';
+                     Buffer.add_char v.buf '{';
                      buffer_space v lexbuf;
                      buffer_object_end v lexbuf;
                      buffer_ident v lexbuf;
@@ -895,7 +895,7 @@ and buffer_json v = parse
                  }
 
   | '['          { try
-                     Bi_outbuf.add_char v.buf '[';
+                     Buffer.add_char v.buf '[';
                      buffer_space v lexbuf;
                      buffer_array_end v lexbuf;
                      buffer_json v lexbuf;
@@ -913,7 +913,7 @@ and buffer_json v = parse
   | '('          {
                    #ifdef TUPLE
                      try
-                       Bi_outbuf.add_char v.buf '(';
+                       Buffer.add_char v.buf '(';
                        buffer_space v lexbuf;
                        buffer_tuple_end v lexbuf;
                        buffer_json v lexbuf;
@@ -933,7 +933,7 @@ and buffer_json v = parse
 
   | '<'          {
                    #ifdef VARIANT
-                     Bi_outbuf.add_char v.buf '<';
+                     Buffer.add_char v.buf '<';
                      buffer_space v lexbuf;
                      buffer_ident v lexbuf;
                      buffer_space v lexbuf;
@@ -944,10 +944,10 @@ and buffer_json v = parse
                  }
 
   | "//"[^'\n']* { add_lexeme v.buf lexbuf; buffer_json v lexbuf }
-  | "/*"         { Bi_outbuf.add_string v.buf "/*";
+  | "/*"         { Buffer.add_string v.buf "/*";
                    finish_buffer_comment v lexbuf;
                    buffer_json v lexbuf }
-  | "\n"         { Bi_outbuf.add_char v.buf '\n';
+  | "\n"         { Buffer.add_char v.buf '\n';
                    newline v lexbuf;
                    buffer_json v lexbuf }
   | space        { add_lexeme v.buf lexbuf; buffer_json v lexbuf }
@@ -958,18 +958,18 @@ and buffer_json v = parse
 and finish_buffer_stringlit v = parse
     ( '\\' (['"' '\\' '/' 'b' 'f' 'n' 'r' 't'] | 'u' hex hex hex hex)
     | [^'"' '\\'] )* '"'
-         { Bi_outbuf.add_char v.buf '"';
+         { Buffer.add_char v.buf '"';
            add_lexeme v.buf lexbuf
          }
   | _    { long_error "Invalid string literal" v lexbuf }
   | eof  { custom_error "Unexpected end of input" v lexbuf }
 
 and finish_buffer_variant v = parse
-    ':'  { Bi_outbuf.add_char v.buf ':';
+    ':'  { Buffer.add_char v.buf ':';
            buffer_json v lexbuf;
            buffer_space v lexbuf;
            buffer_gt v lexbuf }
-  | '>'  { Bi_outbuf.add_char v.buf '>' }
+  | '>'  { Buffer.add_char v.buf '>' }
   | _    { long_error "Expected ':' or '>' but found" v lexbuf }
   | eof  { custom_error "Unexpected end of input" v lexbuf }
 
@@ -985,11 +985,11 @@ and buffer_space v = parse
     newline v lexbuf;
     buffer_space v lexbuf }
   | "/*"                     {
-    Bi_outbuf.add_string v.buf "/*";
+    Buffer.add_string v.buf "/*";
     finish_buffer_comment v lexbuf;
     buffer_space v lexbuf }
   | '\n'                     {
-    Bi_outbuf.add_char v.buf '\n';
+    Buffer.add_char v.buf '\n';
     newline v lexbuf;
     buffer_space v lexbuf }
   | [' ' '\t' '\r']+         {
@@ -999,52 +999,52 @@ and buffer_space v = parse
 
 and buffer_object_end v = parse
     '}'      {
-      Bi_outbuf.add_char v.buf '}';
+      Buffer.add_char v.buf '}';
       raise End_of_object }
   | ""       { () }
 
 and buffer_object_sep v = parse
-    ','      { Bi_outbuf.add_char v.buf ',' }
-  | '}'      { Bi_outbuf.add_char v.buf '}'; raise End_of_object }
+    ','      { Buffer.add_char v.buf ',' }
+  | '}'      { Buffer.add_char v.buf '}'; raise End_of_object }
   | _        { long_error "Expected ',' or '}' but found" v lexbuf }
   | eof      { custom_error "Unexpected end of input" v lexbuf }
 
 and buffer_array_end v = parse
-    ']'      { Bi_outbuf.add_char v.buf ']'; raise End_of_array }
+    ']'      { Buffer.add_char v.buf ']'; raise End_of_array }
   | ""       { () }
 
 and buffer_array_sep v = parse
-    ','      { Bi_outbuf.add_char v.buf ',' }
-  | ']'      { Bi_outbuf.add_char v.buf ']'; raise End_of_array }
+    ','      { Buffer.add_char v.buf ',' }
+  | ']'      { Buffer.add_char v.buf ']'; raise End_of_array }
   | _        { long_error "Expected ',' or ']' but found" v lexbuf }
   | eof      { custom_error "Unexpected end of input" v lexbuf }
 
 and buffer_tuple_end v = parse
     ')'      {
-      Bi_outbuf.add_char v.buf ')';
+      Buffer.add_char v.buf ')';
       raise End_of_tuple }
   | ""       { () }
 
 and buffer_tuple_sep v = parse
-    ','      { Bi_outbuf.add_char v.buf ',' }
-  | ')'      { Bi_outbuf.add_char v.buf ')'; raise End_of_tuple }
+    ','      { Buffer.add_char v.buf ',' }
+  | ')'      { Buffer.add_char v.buf ')'; raise End_of_tuple }
   | _        { long_error "Expected ',' or ')' but found" v lexbuf }
   | eof      { custom_error "Unexpected end of input" v lexbuf }
 
 and buffer_colon v = parse
-    ':'      { Bi_outbuf.add_char v.buf ':' }
+    ':'      { Buffer.add_char v.buf ':' }
   | _        { long_error "Expected ':' but found" v lexbuf }
   | eof      { custom_error "Unexpected end of input" v lexbuf }
 
 and buffer_gt v = parse
-    '>'  { Bi_outbuf.add_char v.buf '>' }
+    '>'  { Buffer.add_char v.buf '>' }
   | _    { long_error "Expected '>' but found" v lexbuf }
   | eof  { custom_error "Unexpected end of input" v lexbuf }
 
 and finish_buffer_comment v = parse
-  | "*/" { Bi_outbuf.add_string v.buf "*/" }
+  | "*/" { Buffer.add_string v.buf "*/" }
   | eof  { long_error "Unterminated comment" v lexbuf }
-  | '\n' { Bi_outbuf.add_char v.buf '\n';
+  | '\n' { Buffer.add_char v.buf '\n';
            newline v lexbuf;
            finish_buffer_comment v lexbuf }
   | _    { add_lexeme v.buf lexbuf; finish_buffer_comment v lexbuf }
@@ -1184,7 +1184,7 @@ and junk = parse
       ?buf ?(fin = fun () -> ()) ?fname ?lnum:(lnum0 = 1) ic =
     let buf =
       match buf with
-          None -> Some (Bi_outbuf.create 256)
+          None -> Some (Buffer.create 256)
         | Some _ -> buf
     in
     let f i =
diff --git a/lib/write.ml b/lib/write.ml
index 30fc4ad1..4692cfbd 100644
--- a/lib/write.ml
+++ b/lib/write.ml
@@ -7,22 +7,20 @@ let hex n =
   )
 
 let write_special src start stop ob str =
-  Bi_outbuf.add_substring ob src !start (stop - !start);
-  Bi_outbuf.add_string ob str;
+  Buffer.add_substring ob src !start (stop - !start);
+  Buffer.add_string ob str;
   start := stop + 1
 
 let write_control_char src start stop ob c =
-  Bi_outbuf.add_substring ob src !start (stop - !start);
-  let i = Bi_outbuf.alloc ob 6 in
-  let dst = ob.o_s in
-  Bytes.blit_string "\\u00" 0 dst i 4;
-  Bytes.set dst (i+4) (hex (Char.code c lsr 4));
-  Bytes.set dst (i+5) (hex (Char.code c land 0xf));
+  Buffer.add_substring ob src !start (stop - !start);
+  Buffer.add_string ob "\\00";
+  Buffer.add_char ob (hex (Char.code c lsr 4));
+  Buffer.add_char ob (hex (Char.code c land 0xf));
   start := stop + 1
 
 let finish_string src start ob =
   try
-    Bi_outbuf.add_substring ob src !start (String.length src - !start)
+    Buffer.add_substring ob src !start (String.length src - !start)
   with exc ->
     Printf.eprintf "src=%S start=%i len=%i\n%!"
       src !start (String.length src - !start);
@@ -46,14 +44,14 @@ let write_string_body ob s =
   finish_string s start ob
 
 let write_string ob s =
-  Bi_outbuf.add_char ob '"';
+  Buffer.add_char ob '"';
   write_string_body ob s;
-  Bi_outbuf.add_char ob '"'
+  Buffer.add_char ob '"'
 
 let json_string_of_string s =
-  let ob = Bi_outbuf.create 10 in
+  let ob = Buffer.create 10 in
   write_string ob s;
-  Bi_outbuf.contents ob
+  Buffer.contents ob
 
 let test_string () =
   let s = Bytes.create 256 in
@@ -64,10 +62,10 @@ let test_string () =
 
 
 let write_null ob () =
-  Bi_outbuf.add_string ob "null"
+  Buffer.add_string ob "null"
 
 let write_bool ob x =
-  Bi_outbuf.add_string ob (if x then "true" else "false")
+  Buffer.add_string ob (if x then "true" else "false")
 
 
 let max_digits =
@@ -78,26 +76,22 @@ let max_digits =
 let dec n =
   Char.chr (n + 48)
 
-let rec write_digits s pos x =
-  if x = 0 then pos
+let rec write_digits s x =
+  if x = 0 then ()
   else
     let d = x mod 10 in
-    let pos = write_digits s pos (x / 10) in
-    Bytes.set s pos (dec (abs d));
-    pos + 1
+    write_digits s (x / 10);
+    Buffer.add_char s (dec (abs d))
 
 let write_int ob x =
-  Bi_outbuf.extend ob max_digits;
   if x > 0 then
-    ob.o_len <- write_digits ob.o_s ob.o_len x
+    write_digits ob x
   else if x < 0 then (
-    let s = ob.o_s in
-    let pos = ob.o_len in
-    Bytes.set s pos '-';
-    ob.o_len <- write_digits s (pos + 1) x
+    Buffer.add_char ob '-';
+    write_digits ob x
   )
   else
-    Bi_outbuf.add_char ob '0'
+    Buffer.add_char ob '0'
 
 
 let json_string_of_int i =
@@ -130,30 +124,30 @@ let float_needs_period s =
 let write_float_fast ob x =
   match classify_float x with
     FP_nan ->
-      Bi_outbuf.add_string ob "NaN"
+      Buffer.add_string ob "NaN"
   | FP_infinite ->
-      Bi_outbuf.add_string ob (if x > 0. then "Infinity" else "-Infinity")
+      Buffer.add_string ob (if x > 0. then "Infinity" else "-Infinity")
   | _ ->
       let s = Printf.sprintf "%.17g" x in
-      Bi_outbuf.add_string ob s;
+      Buffer.add_string ob s;
       if float_needs_period s then
-        Bi_outbuf.add_string ob ".0"
+        Buffer.add_string ob ".0"
 
 let write_float ob x =
   match classify_float x with
     FP_nan ->
-      Bi_outbuf.add_string ob "NaN"
+      Buffer.add_string ob "NaN"
   | FP_infinite ->
-      Bi_outbuf.add_string ob (if x > 0. then "Infinity" else "-Infinity")
+      Buffer.add_string ob (if x > 0. then "Infinity" else "-Infinity")
   | _ ->
       let s1 = Printf.sprintf "%.16g" x in
       let s =
         if float_of_string s1 = x then s1
         else Printf.sprintf "%.17g" x
       in
-      Bi_outbuf.add_string ob s;
+      Buffer.add_string ob s;
       if float_needs_period s then
-        Bi_outbuf.add_string ob ".0"
+        Buffer.add_string ob ".0"
 
 let write_normal_float_prec significant_figures ob x =
   let open Printf in
@@ -177,23 +171,23 @@ let write_normal_float_prec significant_figures ob x =
       | 16 -> sprintf "%.16g" x
       | _ -> sprintf "%.17g" x
   in
-  Bi_outbuf.add_string ob s;
+  Buffer.add_string ob s;
   if float_needs_period s then
-    Bi_outbuf.add_string ob ".0"
+    Buffer.add_string ob ".0"
 
 let write_float_prec significant_figures ob x =
   match classify_float x with
     FP_nan ->
-      Bi_outbuf.add_string ob "NaN"
+      Buffer.add_string ob "NaN"
   | FP_infinite ->
-      Bi_outbuf.add_string ob (if x > 0. then "Infinity" else "-Infinity")
+      Buffer.add_string ob (if x > 0. then "Infinity" else "-Infinity")
   | _ ->
       write_normal_float_prec significant_figures ob x
 
 let json_string_of_float x =
-  let ob = Bi_outbuf.create 20 in
+  let ob = Buffer.create 20 in
   write_float ob x;
-  Bi_outbuf.contents ob
+  Buffer.contents ob
 
 
 let write_std_float_fast ob x =
@@ -208,9 +202,9 @@ let write_std_float_fast ob x =
            "-Infinity value not allowed in standard JSON")
   | _ ->
       let s = Printf.sprintf "%.17g" x in
-      Bi_outbuf.add_string ob s;
+      Buffer.add_string ob s;
       if float_needs_period s then
-        Bi_outbuf.add_string ob ".0"
+        Buffer.add_string ob ".0"
 
 let write_std_float ob x =
   match classify_float x with
@@ -228,9 +222,9 @@ let write_std_float ob x =
         if float_of_string s1 = x then s1
         else Printf.sprintf "%.17g" x
       in
-      Bi_outbuf.add_string ob s;
+      Buffer.add_string ob s;
       if float_needs_period s then
-        Bi_outbuf.add_string ob ".0"
+        Buffer.add_string ob ".0"
 
 let write_std_float_prec significant_figures ob x =
   match classify_float x with
@@ -246,9 +240,9 @@ let write_std_float_prec significant_figures ob x =
       write_normal_float_prec significant_figures ob x
 
 let std_json_string_of_float x =
-  let ob = Bi_outbuf.create 20 in
+  let ob = Buffer.create 20 in
   write_std_float ob x;
-  Bi_outbuf.contents ob
+  Buffer.contents ob
 
 
 let test_float () =
@@ -271,9 +265,9 @@ let test_float () =
 let () = test_float ()
 *)
 
-let write_intlit = Bi_outbuf.add_string
-let write_floatlit = Bi_outbuf.add_string
-let write_stringlit = Bi_outbuf.add_string
+let write_intlit = Buffer.add_string
+let write_floatlit = Buffer.add_string
+let write_stringlit = Buffer.add_string
 
 let rec iter2_aux f_elt f_sep x = function
     [] -> ()
@@ -289,7 +283,7 @@ let iter2 f_elt f_sep x = function
       iter2_aux f_elt f_sep x l
 
 let f_sep ob =
-  Bi_outbuf.add_char ob ','
+  Buffer.add_char ob ','
 
 let rec write_json ob (x : t) =
   match x with
@@ -299,19 +293,19 @@ let rec write_json ob (x : t) =
     | `Int i -> write_int ob i
 #endif
 #ifdef INTLIT
-    | `Intlit s -> Bi_outbuf.add_string ob s
+    | `Intlit s -> Buffer.add_string ob s
 #endif
 #ifdef FLOAT
     | `Float f -> write_float ob f
 #endif
 #ifdef FLOATLIT
-    | `Floatlit s -> Bi_outbuf.add_string ob s
+    | `Floatlit s -> Buffer.add_string ob s
 #endif
 #ifdef STRING
     | `String s -> write_string ob s
 #endif
 #ifdef STRINGLIT
-    | `Stringlit s -> Bi_outbuf.add_string ob s
+    | `Stringlit s -> Buffer.add_string ob s
 #endif
     | `Assoc l -> write_assoc ob l
     | `List l -> write_list ob l
@@ -325,36 +319,36 @@ let rec write_json ob (x : t) =
 and write_assoc ob l =
   let f_elt ob (s, x) =
     write_string ob s;
-    Bi_outbuf.add_char ob ':';
+    Buffer.add_char ob ':';
     write_json ob x
   in
-  Bi_outbuf.add_char ob '{';
+  Buffer.add_char ob '{';
   iter2 f_elt f_sep ob l;
-  Bi_outbuf.add_char ob '}';
+  Buffer.add_char ob '}';
 
 and write_list ob l =
-  Bi_outbuf.add_char ob '[';
+  Buffer.add_char ob '[';
   iter2 write_json f_sep ob l;
-  Bi_outbuf.add_char ob ']'
+  Buffer.add_char ob ']'
 
 #ifdef TUPLE
 and write_tuple ob l =
-  Bi_outbuf.add_char ob '(';
+  Buffer.add_char ob '(';
   iter2 write_json f_sep ob l;
-  Bi_outbuf.add_char ob ')'
+  Buffer.add_char ob ')'
 #endif
 
 #ifdef VARIANT
 and write_variant ob s o =
-  Bi_outbuf.add_char ob '<';
+  Buffer.add_char ob '<';
   write_string ob s;
   (match o with
        None -> ()
      | Some x ->
-         Bi_outbuf.add_char ob ':';
+         Buffer.add_char ob ':';
          write_json ob x
   );
-  Bi_outbuf.add_char ob '>'
+  Buffer.add_char ob '>'
 #endif
 
 let write_t = write_json
@@ -367,19 +361,19 @@ let rec write_std_json ob (x : t) =
     | `Int i -> write_int ob i
 #endif
 #ifdef INTLIT
-    | `Intlit s -> Bi_outbuf.add_string ob s
+    | `Intlit s -> Buffer.add_string ob s
 #endif
 #ifdef FLOAT
     | `Float f -> write_std_float ob f
 #endif
 #ifdef FLOATLIT
-    | `Floatlit s -> Bi_outbuf.add_string ob s
+    | `Floatlit s -> Buffer.add_string ob s
 #endif
 #ifdef STRING
     | `String s -> write_string ob s
 #endif
 #ifdef STRINGLIT
-    | `Stringlit s -> Bi_outbuf.add_string ob s
+    | `Stringlit s -> Buffer.add_string ob s
 #endif
     | `Assoc l -> write_std_assoc ob l
     | `List l -> write_std_list ob l
@@ -393,33 +387,33 @@ let rec write_std_json ob (x : t) =
 and write_std_assoc ob l =
   let f_elt ob (s, x) =
     write_string ob s;
-    Bi_outbuf.add_char ob ':';
+    Buffer.add_char ob ':';
     write_std_json ob x
   in
-  Bi_outbuf.add_char ob '{';
+  Buffer.add_char ob '{';
   iter2 f_elt f_sep ob l;
-  Bi_outbuf.add_char ob '}';
+  Buffer.add_char ob '}';
 
 and write_std_list ob l =
-  Bi_outbuf.add_char ob '[';
+  Buffer.add_char ob '[';
   iter2 write_std_json f_sep ob l;
-  Bi_outbuf.add_char ob ']'
+  Buffer.add_char ob ']'
 
 and write_std_tuple ob l =
-  Bi_outbuf.add_char ob '[';
+  Buffer.add_char ob '[';
   iter2 write_std_json f_sep ob l;
-  Bi_outbuf.add_char ob ']'
+  Buffer.add_char ob ']'
 
 #ifdef VARIANT
 and write_std_variant ob s o =
   match o with
       None -> write_string ob s
     | Some x ->
-        Bi_outbuf.add_char ob '[';
+        Buffer.add_char ob '[';
         write_string ob s;
-        Bi_outbuf.add_char ob ',';
+        Buffer.add_char ob ',';
         write_std_json ob x;
-        Bi_outbuf.add_char ob ']'
+        Buffer.add_char ob ']'
 #endif
 
 
@@ -437,33 +431,31 @@ let to_outbuf ?(std = false) ob x =
 let to_string ?buf ?(len = 256) ?std x =
   let ob =
     match buf with
-        None -> Bi_outbuf.create len
+        None -> Buffer.create len
       | Some ob ->
-          Bi_outbuf.clear ob;
+          Buffer.clear ob;
           ob
   in
   to_outbuf ?std ob x;
-  let s = Bi_outbuf.contents ob in
-  Bi_outbuf.clear ob;
+  let s = Buffer.contents ob in
+  Buffer.clear ob;
   s
 
-let to_channel ?buf ?len ?std oc x =
+let to_channel ?buf ?(len=4096) ?std oc x =
   let ob =
     match buf with
-        None -> Bi_outbuf.create_channel_writer ?len oc
+        None -> Buffer.create len
       | Some ob -> ob
   in
-  to_outbuf ?std ob x;
-  Bi_outbuf.flush_channel_writer ob
+  to_outbuf ?std ob x
 
-let to_output ?buf ?len ?std out x =
+let to_output ?buf ?(len=4096) ?std out x =
   let ob =
     match buf with
-        None -> Bi_outbuf.create_output_writer ?len out
+        None -> Buffer.create len
       | Some ob -> ob
   in
-  to_outbuf ?std ob x;
-  Bi_outbuf.flush_output_writer ob
+  to_outbuf ?std ob x
 
 let to_file ?len ?std file x =
   let oc = open_out file in
@@ -480,24 +472,23 @@ let stream_to_outbuf ?std ob st =
 let stream_to_string ?buf ?(len = 256) ?std st =
   let ob =
     match buf with
-        None -> Bi_outbuf.create len
+        None -> Buffer.create len
       | Some ob ->
-          Bi_outbuf.clear ob;
+          Buffer.clear ob;
           ob
   in
   stream_to_outbuf ?std ob st;
-  let s = Bi_outbuf.contents ob in
-  Bi_outbuf.clear ob;
+  let s = Buffer.contents ob in
+  Buffer.clear ob;
   s
 
-let stream_to_channel ?buf ?len ?std oc st =
+let stream_to_channel ?buf ?(len=2096) ?std oc st =
   let ob =
     match buf with
-        None -> Bi_outbuf.create_channel_writer ?len oc
+        None -> Buffer.create len
       | Some ob -> ob
   in
-  stream_to_outbuf ?std ob st;
-  Bi_outbuf.flush_channel_writer ob
+  stream_to_outbuf ?std ob st
 
 let stream_to_file ?len ?std file st =
   let oc = open_out file in
diff --git a/lib/write.mli b/lib/write.mli
index b8515a8b..4b0970f7 100644
--- a/lib/write.mli
+++ b/lib/write.mli
@@ -1,13 +1,13 @@
 (** {2 JSON writers} *)
 
 val to_string :
-  ?buf:Bi_outbuf.t ->
+  ?buf:Buffer.t ->
   ?len:int ->
   ?std:bool ->
   t -> string
   (** Write a compact JSON value to a string.
       @param buf allows to reuse an existing buffer created with
-      [Bi_outbuf.create]. The buffer is cleared of all contents
+      [Buffer.create]. The buffer is cleared of all contents
       before starting and right before returning.
       @param len initial length of the output buffer.
       @param std use only standard JSON syntax,
@@ -18,13 +18,13 @@ val to_string :
   *)
 
 val to_channel :
-  ?buf:Bi_outbuf.t ->
+  ?buf:Buffer.t ->
   ?len:int ->
   ?std:bool ->
   out_channel -> t -> unit
   (** Write a compact JSON value to a channel.
       @param buf allows to reuse an existing buffer created with
-      [Bi_outbuf.create_channel_writer] on the same channel.
+      [Buffer.create] on the same channel.
       [buf] is flushed right
       before [to_channel] returns but the [out_channel] is
       not flushed automatically.
@@ -32,13 +32,13 @@ val to_channel :
       See [to_string] for the role of the other optional arguments. *)
 
 val to_output :
-  ?buf:Bi_outbuf.t ->
+  ?buf:Buffer.t ->
   ?len:int ->
   ?std:bool ->
   < output : string -> int -> int -> int; .. > -> t -> unit
   (** Write a compact JSON value to an OO channel.
       @param buf allows to reuse an existing buffer created with
-      [Bi_outbuf.create_output_writer] on the same channel.
+      [Buffer.add_channel] on the same channel.
       [buf] is flushed right
       before [to_output] returns but the channel itself is
       not flushed automatically.
@@ -54,12 +54,12 @@ val to_file :
 
 val to_outbuf :
   ?std:bool ->
-  Bi_outbuf.t -> t -> unit
+  Buffer.t -> t -> unit
   (** Write a compact JSON value to an existing buffer.
       See [to_string] for the role of the optional argument. *)
 
 val stream_to_string :
-  ?buf:Bi_outbuf.t ->
+  ?buf:Buffer.t ->
   ?len:int ->
   ?std:bool ->
   t Stream.t -> string
@@ -68,7 +68,7 @@ val stream_to_string :
       See [to_string] for the role of the optional arguments. *)
 
 val stream_to_channel :
-  ?buf:Bi_outbuf.t ->
+  ?buf:Buffer.t ->
   ?len:int ->
   ?std:bool ->
   out_channel -> t Stream.t -> unit
@@ -86,7 +86,7 @@ val stream_to_file :
 
 val stream_to_outbuf :
   ?std:bool ->
-  Bi_outbuf.t ->
+  Buffer.t ->
   t Stream.t -> unit
   (** Write a newline-separated sequence of compact one-line JSON values to
       an existing buffer.
@@ -107,46 +107,46 @@ val sort : t -> t
 (**/**)
 (* begin undocumented section *)
 
-val write_null : Bi_outbuf.t -> unit -> unit
-val write_bool : Bi_outbuf.t -> bool -> unit
+val write_null : Buffer.t -> unit -> unit
+val write_bool : Buffer.t -> bool -> unit
 #ifdef INT
-val write_int : Bi_outbuf.t -> int -> unit
+val write_int : Buffer.t -> int -> unit
 #endif
 #ifdef FLOAT
-val write_float : Bi_outbuf.t -> float -> unit
-val write_std_float : Bi_outbuf.t -> float -> unit
-val write_float_fast : Bi_outbuf.t -> float -> unit
-val write_std_float_fast : Bi_outbuf.t -> float -> unit
-val write_float_prec : int -> Bi_outbuf.t -> float -> unit
-val write_std_float_prec : int -> Bi_outbuf.t -> float -> unit
+val write_float : Buffer.t -> float -> unit
+val write_std_float : Buffer.t -> float -> unit
+val write_float_fast : Buffer.t -> float -> unit
+val write_std_float_fast : Buffer.t -> float -> unit
+val write_float_prec : int -> Buffer.t -> float -> unit
+val write_std_float_prec : int -> Buffer.t -> float -> unit
 #endif
 #ifdef STRING
-val write_string : Bi_outbuf.t -> string -> unit
+val write_string : Buffer.t -> string -> unit
 #endif
 
 #ifdef INTLIT
-val write_intlit : Bi_outbuf.t -> string -> unit
+val write_intlit : Buffer.t -> string -> unit
 #endif
 #ifdef FLOATLIT
-val write_floatlit : Bi_outbuf.t -> string -> unit
+val write_floatlit : Buffer.t -> string -> unit
 #endif
 #ifdef STRINGLIT
-val write_stringlit : Bi_outbuf.t -> string -> unit
+val write_stringlit : Buffer.t -> string -> unit
 #endif
 
-val write_assoc : Bi_outbuf.t -> (string * t) list -> unit
-val write_list : Bi_outbuf.t -> t list -> unit
+val write_assoc : Buffer.t -> (string * t) list -> unit
+val write_list : Buffer.t -> t list -> unit
 #ifdef TUPLE
-val write_tuple : Bi_outbuf.t -> t list -> unit
-val write_std_tuple : Bi_outbuf.t -> t list -> unit
+val write_tuple : Buffer.t -> t list -> unit
+val write_std_tuple : Buffer.t -> t list -> unit
 #endif
 #ifdef VARIANT
-val write_variant : Bi_outbuf.t -> string -> t option -> unit
-val write_std_variant : Bi_outbuf.t -> string -> t option -> unit
+val write_variant : Buffer.t -> string -> t option -> unit
+val write_std_variant : Buffer.t -> string -> t option -> unit
 #endif
 
-val write_json : Bi_outbuf.t -> t -> unit
-val write_std_json : Bi_outbuf.t -> t -> unit
+val write_json : Buffer.t -> t -> unit
+val write_std_json : Buffer.t -> t -> unit
 
 (* end undocumented section *)
 (**/**)
diff --git a/yojson-biniou.opam b/yojson-biniou.opam
new file mode 100644
index 00000000..194ab742
--- /dev/null
+++ b/yojson-biniou.opam
@@ -0,0 +1,23 @@
+opam-version: "2.0"
+maintainer: "nathan@cryptosense.com"
+authors: ["Martin Jambon"]
+homepage: "https://github.com/ocaml-community/yojson"
+bug-reports: "https://github.com/ocaml-community/yojson/issues"
+dev-repo: "git+https://github.com/ocaml-community/yojson.git"
+doc: "https://ocaml-community.github.io/yojson/"
+build: [
+  ["dune" "subst"] {pinned}
+  ["dune" "build" "-p" name "-j" jobs]
+]
+depends: [
+  "ocaml" {>= "4.02.3"}
+  "dune" {build}
+  "yojson" {= version}
+  "biniou" {>= "1.2.0"}
+]
+synopsis:
+  "Yojson-biniou provides Biniou support for Yojson"
+description: """
+Yojson-biniou provides Biniou support for Yojson.
+
+It used to be part of the main Yojson package but was spun off."""
diff --git a/yojson-biniou/lib/dune b/yojson-biniou/lib/dune
new file mode 100644
index 00000000..34c52942
--- /dev/null
+++ b/yojson-biniou/lib/dune
@@ -0,0 +1,6 @@
+(library
+ (name yojson_biniou)
+ (public_name yojson-biniou)
+ (synopsis "Biniou support for Yojson")
+ (flags (-safe-string))
+ (libraries yojson biniou))
diff --git a/lib/yojson_biniou.ml b/yojson-biniou/lib/yojson_biniou.ml
similarity index 100%
rename from lib/yojson_biniou.ml
rename to yojson-biniou/lib/yojson_biniou.ml
diff --git a/lib/yojson_biniou.mli b/yojson-biniou/lib/yojson_biniou.mli
similarity index 100%
rename from lib/yojson_biniou.mli
rename to yojson-biniou/lib/yojson_biniou.mli
diff --git a/yojson.opam b/yojson.opam
index 46b5ceaa..408b50a9 100644
--- a/yojson.opam
+++ b/yojson.opam
@@ -1,5 +1,5 @@
 opam-version: "2.0"
-maintainer: "martin@mjambon.com"
+maintainer: "nathan@cryptosense.com"
 authors: ["Martin Jambon"]
 homepage: "https://github.com/ocaml-community/yojson"
 bug-reports: "https://github.com/ocaml-community/yojson/issues"
@@ -14,7 +14,6 @@ depends: [
   "ocaml" {>= "4.02.3"}
   "dune"
   "cppo" {build}
-  "biniou" {>= "1.2.0"}
   "alcotest" {with-test & >= "0.8.5"}
 ]
 synopsis: