diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 3fff1e46..8ae8cd44 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -15,6 +15,7 @@ jobs:
       fail-fast: false
       matrix:
         ocaml-compiler:
+          - 4.10.0
           - 4.11.0
           - 4.12.0
           - 4.13.0
diff --git a/README.md b/README.md
index ff1c9466..d67ebd5c 100644
--- a/README.md
+++ b/README.md
@@ -71,7 +71,7 @@ opam pin add jupyter https://github.com/akabe/ocaml-jupyter.git
 - [Introduction](https://github.com/akabe/ocaml-jupyter/blob/master/notebooks/introduction.ipynb):
   a very simple example for use of OCaml Jupyter and sub-packages.
 - [Get a description of a word from DuckDuckGo API](https://github.com/akabe/ocaml-jupyter/blob/master/notebooks/word_description_from_DuckDuckGoAPI.ipynb):
-  request to DuckDuckGo API server by `cohttp.lwt`, and parse a response JSON by `yojson` and `ppx_deriving_yojson`.
+  request to DuckDuckGo API server by `cohttp.lwt`, and parse a response JSON by `yojson` and `ppx_yojson_conv`.
 
 In addition, many examples (e.g, image processing, voice analysis, etc.) are available at
 [docker-ocaml-jupyter-datascience/notebooks](https://github.com/akabe/docker-ocaml-jupyter-datascience/tree/master/notebooks).
diff --git a/config/dune b/config/dune
index c73c7e4c..e67d926d 100644
--- a/config/dune
+++ b/config/dune
@@ -14,10 +14,8 @@
  (targets ocaml_flags.sexp)
  (deps    configure.exe)
  (action  (run %{deps} -o %{targets}
-               -ppx ppx_deriving_yojson
-               -ppx lwt_ppx
                -ocamlfind %{bin:ocamlfind}
-               -ocaml-flag "-w A-4-31-33-34-39-41-42-43-44-45-48-49-50-58"
+               -ocaml-flag "-w A-4-31-33-34-39-41-42-43-44-45-48-49-50-58-66"
                -ocaml-flag "-safe-string -strict-sequence -strict-formats"
                -ocaml-flag "-short-paths")))
 
diff --git a/jupyter-archimedes/src/dune b/jupyter-archimedes/src/dune
index 84d52195..af632616 100644
--- a/jupyter-archimedes/src/dune
+++ b/jupyter-archimedes/src/dune
@@ -5,6 +5,5 @@
  (modes       byte)
  (modules     Jupyter_archimedes)
  (flags       ((:include %{workspace_root}/config/ocaml_flags.sexp)))
- (preprocess  (pps ppx_deriving_yojson))
  (libraries   jupyter.notebook
               archimedes.cairo))
diff --git a/jupyter.opam b/jupyter.opam
index ba728192..03ec8a67 100644
--- a/jupyter.opam
+++ b/jupyter.opam
@@ -17,7 +17,7 @@ build: [
   [ "dune" "build" "-p" name "-j" jobs ]
 ]
 depends: [
-  "ocaml" {>= "4.04.0" & < "4.15"}
+  "ocaml" {>= "4.10.0" & < "4.15"}
   "base-threads"
   "base-unix"
   "uuidm" {>= "0.9.6"}
@@ -29,11 +29,12 @@ depends: [
   "zmq" {>= "5.0.0"}
   "zmq-lwt" {>= "5.0.0"}
   "yojson" {>="1.6.0"}
-  "ppx_deriving_yojson" {>= "3.0"}
+  "ppx_yojson_conv" {>= "0.14.0"}
   "cryptokit" {>= "1.12"}
   "dune" {build & >= "1.0.0"}
   "ounit2" {with-test & >= "2.0.0"}
   "ocp-indent" {with-test & >= "1.7.0"}
+  "ppx_deriving" {with-test}
 ]
 depopts: [
   "merlin"
diff --git a/jupyter/src/comm/dune b/jupyter/src/comm/dune
index ccf5c36f..093e28ec 100644
--- a/jupyter/src/comm/dune
+++ b/jupyter/src/comm/dune
@@ -10,6 +10,6 @@
  (flags       (:standard
                -thread
                (:include %{workspace_root}/config/ocaml_flags.sexp)))
- (preprocess  (pps ppx_deriving_yojson))
+ (preprocess  (pps ppx_yojson_conv))
  (libraries   jupyter
               jupyter.notebook))
diff --git a/jupyter/src/completor/dune b/jupyter/src/completor/dune
index 61cd9ae7..8f3c9cc9 100644
--- a/jupyter/src/completor/dune
+++ b/jupyter/src/completor/dune
@@ -5,10 +5,10 @@
               Merlin
               Intf)
  (flags       ((:include %{workspace_root}/config/ocaml_flags.sexp)))
- (preprocess  (pps lwt_ppx ppx_deriving_yojson))
+ (preprocess  (pps lwt_ppx ppx_yojson_conv))
  (libraries   jupyter
               jupyter_log
               lwt
               lwt.unix
               yojson
-              ppx_deriving_yojson.runtime))
+              ppx_yojson_conv_lib))
diff --git a/jupyter/src/completor/intf.ml b/jupyter/src/completor/intf.ml
index 16d6b741..8a08cab6 100644
--- a/jupyter/src/completor/intf.ml
+++ b/jupyter/src/completor/intf.ml
@@ -45,7 +45,7 @@ sig
       cmpl_type : string;
       cmpl_doc  : string;
     }
-  [@@deriving yojson { strict = false }]
+  [@@deriving yojson]
 
   type reply =
     {
@@ -53,7 +53,7 @@ sig
       cmpl_start : int;
       cmpl_end : int;
     }
-  [@@deriving yojson { strict = false }]
+  [@@deriving yojson]
 
   type t
 
diff --git a/jupyter/src/completor/merlin.ml b/jupyter/src/completor/merlin.ml
index 995a2420..e2bfc363 100644
--- a/jupyter/src/completor/merlin.ml
+++ b/jupyter/src/completor/merlin.ml
@@ -73,9 +73,9 @@ let call merlin command flags printer =
 
 type 'a merlin_reply =
   | RETURN of 'a [@name "return"]
-  | FAILURE of Yojson.Safe.t [@name "failure"]
-  | ERROR of Yojson.Safe.t [@name "error"]
-  | EXN of Yojson.Safe.t [@name "exception"]
+  | FAILURE of Jupyter.Json.t [@name "failure"]
+  | ERROR of Jupyter.Json.t [@name "error"]
+  | EXN of Jupyter.Json.t [@name "exception"]
 [@@deriving of_yojson]
 
 type 'a merlin_reply_body =
@@ -84,18 +84,17 @@ type 'a merlin_reply_body =
     value : 'a;
     notifications : string list;
   }
-[@@deriving of_yojson { strict = false }]
+[@@deriving of_yojson]
+[@@yojson.allow_extra_fields]
 
 let parse_merlin_reply ~of_yojson str =
   let error_json msg json =
     error (fun pp -> pp "%s: %s" msg (Yojson.Safe.pretty_to_string json))
   in
   let reply = Yojson.Safe.from_string str
-              |> [%of_yojson: Yojson.Safe.t merlin_reply_body]
-              |> Jupyter.Json.or_die in
+              |> [%of_yojson: Jupyter.Json.t merlin_reply_body] in
   `List [`String reply.klass; reply.value]
   |> merlin_reply_of_yojson of_yojson
-  |> Jupyter.Json.or_die
   |> function
   | RETURN ret -> Some ret
   | FAILURE j -> error_json "Merlin failure" j ; None
@@ -109,14 +108,16 @@ type ident_position =
     id_line : int [@key "line"];
     id_col : int [@key "col"];
   }
-[@@deriving yojson { strict = false }]
+[@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 type ident_reply =
   {
     id_start : ident_position [@key "start"];
     id_end : ident_position [@key "end"];
   }
-[@@deriving yojson { strict = false }]
+[@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 let occurrences ~pos merlin code =
   let args = ["-identifier-at"; string_of_int pos] in
@@ -164,7 +165,8 @@ type candidate =
     cmpl_type : string [@key "desc"];
     cmpl_doc  : string [@key "info"];
   }
-[@@deriving yojson { strict = false }]
+[@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 type reply =
   {
@@ -172,7 +174,8 @@ type reply =
     cmpl_start : int [@key "start"] [@default 0];
     cmpl_end : int [@key "end"] [@default 0];
   }
-[@@deriving yojson { strict = false }]
+[@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 let empty = { cmpl_candidates = []; cmpl_start = 0; cmpl_end = 0; }
 
diff --git a/jupyter/src/core/comm.ml b/jupyter/src/core/comm.ml
index 04e30e55..4c1fdd96 100644
--- a/jupyter/src/core/comm.ml
+++ b/jupyter/src/core/comm.ml
@@ -25,5 +25,7 @@ type t =
   {
     comm_target : string option [@key "target_name"] [@default None];
     comm_id : string [@key "comm_id"];
-    comm_data : Yojson.Safe.t [@key "data"];
-  } [@@deriving yojson { strict = false }]
+    comm_data : Json.t [@key "data"];
+  }
+[@@deriving yojson]
+[@@yojson.allow_extra_fields]
diff --git a/jupyter/src/core/dune b/jupyter/src/core/dune
index 7bee10ce..7a09e44c 100644
--- a/jupyter/src/core/dune
+++ b/jupyter/src/core/dune
@@ -12,5 +12,5 @@
               Json
               Version)
  (flags       ((:include %{workspace_root}/config/ocaml_flags.sexp)))
- (preprocess  (pps ppx_deriving_yojson))
- (libraries   unix uuidm ppx_deriving_yojson.runtime))
+ (preprocess  (pps ppx_yojson_conv))
+ (libraries   unix uuidm ppx_yojson_conv_lib))
diff --git a/jupyter/src/core/iopub.ml b/jupyter/src/core/iopub.ml
index 782f0704..816a67b4 100644
--- a/jupyter/src/core/iopub.ml
+++ b/jupyter/src/core/iopub.ml
@@ -27,27 +27,30 @@
 type stream_name =
   | IOPUB_STDOUT [@name "stdout"]
   | IOPUB_STDERR [@name "stderr"]
-[@@deriving yojson { strict = false }]
+[@@deriving yojson]
 
 type stream =
   {
     stream_name : stream_name Json.enum [@key "name"];
     stream_text : string [@key "text"];
-  } [@@deriving yojson { strict = false }]
+  } [@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 (** {2 Display data} *)
 
 type transient =
   {
     display_id : string [@key "display_id"];
-  } [@@deriving yojson { strict = false }]
+  } [@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 type display_data =
   {
-    display_data : Yojson.Safe.t [@key "data"];
-    display_metadata : Yojson.Safe.t [@key "metadata"];
+    display_data : Json.t [@key "data"];
+    display_metadata : Json.t [@key "metadata"];
     display_transient : transient option [@key "transient"] [@default None];
-  } [@@deriving yojson { strict = false }]
+  } [@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 (** {2 Code inputs} *)
 
@@ -55,16 +58,18 @@ type exec_input =
   {
     exin_code : string [@key "code"];
     exin_count : int [@key "execution_count"];
-  } [@@deriving yojson { strict = false }]
+  } [@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 (** {2 Execution results} *)
 
 type exec_result =
   {
     exres_count : int [@key "execution_count"];
-    exres_data : Yojson.Safe.t [@key "data"];
-    exres_metadata : Yojson.Safe.t [@key "metadata"];
-  } [@@deriving yojson { strict = false }]
+    exres_data : Json.t [@key "data"];
+    exres_metadata : Json.t [@key "metadata"];
+  } [@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 (** {2 Kernel status} *)
 
@@ -77,7 +82,8 @@ type exec_status =
 type status =
   {
     kernel_state : exec_status Json.enum [@key "execution_state"];
-  } [@@deriving yojson { strict = false }]
+  } [@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 (** {2 Execution errors} *)
 
@@ -86,14 +92,16 @@ type error =
     ename : string [@key "ename"];
     evalue : string [@key "evalue"];
     traceback : string list [@key "traceback"];
-  } [@@deriving yojson { strict = false }]
+  } [@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 (** {2 Clear output} *)
 
 type clear_output =
   {
     clear_wait : bool [@key "wait"];
-  } [@@deriving yojson { strict = false }]
+  } [@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 (** {2 IOPUB Request} *)
 
diff --git a/jupyter/src/core/json.ml b/jupyter/src/core/json.ml
index e7fa4595..026c6725 100644
--- a/jupyter/src/core/json.ml
+++ b/jupyter/src/core/json.ml
@@ -22,18 +22,22 @@
 
 (** JSON utility *)
 
-let or_none = function
-  | Result.Error _ -> None
-  | Result.Ok x -> Some x
-
-let or_die = function
-  | Result.Error msg -> Yojson.json_error msg
-  | Result.Ok x -> x
-
 type 'a enum = 'a
 
 let enum_of_yojson of_yojson json = of_yojson (`List [json])
 
-let enum_to_yojson to_yojson x = match to_yojson x with
+let yojson_of_enum yojson_of x = match yojson_of x with
   | `List [json] -> json
-  | _ -> assert false
+  | _ -> assert false (* TODO: replace with a suitable exception *)
+
+type t = Yojson.Safe.t
+
+let yojson_of_t x = x
+
+let t_of_yojson x = x
+
+type 'a option_try = 'a option
+
+let option_try_of_yojson of_yojson x =
+  try Some (of_yojson x)
+  with _ -> None
diff --git a/jupyter/src/core/json.mli b/jupyter/src/core/json.mli
index e286ebc3..e5d9818a 100644
--- a/jupyter/src/core/json.mli
+++ b/jupyter/src/core/json.mli
@@ -22,8 +22,12 @@
 
 (** JSON utility *)
 
-val or_none : ('a, string) Result.result -> 'a option
+type 'a enum = 'a [@@deriving yojson]
 
-val or_die : ('a, string) Result.result -> 'a
+type t = Yojson.Safe.t
 
-type 'a enum = 'a [@@deriving yojson]
+val yojson_of_t : t -> Yojson.Safe.t
+
+val t_of_yojson : Yojson.Safe.t -> t
+
+type 'a option_try = 'a option [@@deriving of_yojson]
diff --git a/jupyter/src/core/message.ml b/jupyter/src/core/message.ml
index efd200db..832a12ea 100644
--- a/jupyter/src/core/message.ml
+++ b/jupyter/src/core/message.ml
@@ -33,20 +33,19 @@ type header =
                                               the message is created *)
     username : string; (** the current username *)
     version : string; (** the message protocol version *)
-  } [@@deriving yojson { strict = false }]
+  } [@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 let header_of_string str =
   Yojson.Safe.from_string str
   |> [%of_yojson: header]
-  |> Json.or_die
 
-let header_option_of_string s =
-  Yojson.Safe.from_string s
-  |> [%of_yojson: header]
-  |> Json.or_none
+let header_option_of_string str =
+  Yojson.Safe.from_string str
+  |> [%of_yojson: header Json.option_try]
 
 let string_of_header hdr =
-  [%to_yojson: header] hdr
+  [%yojson_of: header] hdr
   |> Yojson.Safe.to_string
 
 let string_of_header_option = function
@@ -81,7 +80,8 @@ type 'content t =
     buffers : string list;
     (** optional: buffers is a list of binary data buffers for implementations
         that support binary extensions to the protocol. *)
-  } [@@deriving yojson { strict = false }]
+  } [@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 let epoch_to_iso8601_string epoch =
   let open Unix in
@@ -108,13 +108,13 @@ let create_next ?(time = Unix.gettimeofday ()) ~content_to_yojson parent content
   }
 
 let create_next_shell ?time parent content =
-  create_next ?time ~content_to_yojson:[%to_yojson: Shell.reply] parent content
+  create_next ?time ~content_to_yojson:[%yojson_of: Shell.reply] parent content
 
 let create_next_iopub ?time parent content =
-  create_next ?time ~content_to_yojson:[%to_yojson: Iopub.reply] parent content
+  create_next ?time ~content_to_yojson:[%yojson_of: Iopub.reply] parent content
 
 let create_next_stdin ?time parent content =
-  create_next ?time ~content_to_yojson:[%to_yojson: Stdin.reply] parent content
+  create_next ?time ~content_to_yojson:[%yojson_of: Stdin.reply] parent content
 
 (** {2 Messages} *)
 
diff --git a/jupyter/src/core/shell.ml b/jupyter/src/core/shell.ml
index 0c2e143e..4ecc54c9 100644
--- a/jupyter/src/core/shell.ml
+++ b/jupyter/src/core/shell.ml
@@ -35,16 +35,18 @@ type exec_request =
     exec_code : string [@key "code"];
     exec_silent : bool [@key "silent"];
     exec_store_history : bool [@key "store_history"];
-    exec_user_expr : Yojson.Safe.t [@key "user_expressions"];
+    exec_user_expr : Json.t [@key "user_expressions"];
     exec_allow_stdin : bool [@key "allow_stdin"] [@default true];
     exec_stop_on_error : bool [@key "stop_on_error"] [@default false];
-  } [@@deriving yojson { strict = false }]
+  } [@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 type exec_reply =
   {
     exec_count : int [@key "execution_count"];
     exec_status : status Json.enum [@key "status"];
-  } [@@deriving yojson { strict = false }]
+  } [@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 (** {2 Instrospection} *)
 
@@ -53,15 +55,17 @@ type inspect_request =
     insp_code : string [@key "code"];
     insp_pos : int [@key "cursor_pos"];
     insp_detail : int [@key "detail_level"] [@default 0];
-  } [@@deriving yojson { strict = false }]
+  } [@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 type inspect_reply =
   {
     insp_status : status Json.enum [@key "status"];
     insp_found : bool [@key "found"];
-    insp_data : Yojson.Safe.t [@key "data"] [@default `Null];
-    insp_metadata : Yojson.Safe.t [@key "metadata"] [@default `Null];
-  } [@@deriving yojson { strict = false }]
+    insp_data : Json.t [@key "data"] [@default `Null];
+    insp_metadata : Json.t [@key "metadata"] [@default `Null];
+  } [@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 (** {2 Completion} *)
 
@@ -69,16 +73,18 @@ type complete_request =
   {
     cmpl_code : string [@key "code"];
     cmpl_pos : int [@key "cursor_pos"];
-  } [@@deriving yojson { strict = false }]
+  } [@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 type complete_reply =
   {
     cmpl_matches : string list [@key "matches"];
     cmpl_start : int [@key "cursor_start"];
     cmpl_end : int [@key "cursor_end"];
-    cmpl_metadata : Yojson.Safe.t [@key "metadata"];
+    cmpl_metadata : Json.t [@key "metadata"];
     cmpl_status : status Json.enum [@key "status"];
-  } [@@deriving yojson { strict = false }]
+  } [@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 (** {2 History} *)
 
@@ -93,25 +99,29 @@ type history_request =
     hist_n : int [@key "n"];
     hist_pattern : string option [@key "pattern"] [@default None];
     hist_unique : bool [@key "unique"] [@default false];
-  } [@@deriving yojson { strict = false }]
+  } [@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 type history_reply =
   {
     history : (int option * int * string) list;
-  } [@@deriving yojson { strict = false }]
+  } [@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 (** {2 Code completeness} *)
 
 type is_complete_request =
   {
     is_cmpl_code : string [@key "code"];
-  } [@@deriving yojson { strict = false }]
+  } [@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 type is_complete_reply =
   {
     is_cmpl_status : string [@key "status"];
     is_cmpl_indent : string option [@key "indent"] [@default None];
-  } [@@deriving yojson { strict = false }]
+  } [@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 (** {2 Connect} *)
 
@@ -122,19 +132,22 @@ type connect_reply =
     conn_stdin_port : int [@key "stdin_port"];
     conn_hb_port : int [@key "hb_port"];
     conn_ctrl_port : int [@key "control_port"];
-  } [@@deriving yojson { strict = false }]
+  } [@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 (** {2 Comm info} *)
 
 type comm_info_request =
   {
     ci_target : string option [@key "target_name"] [@default None];
-  } [@@deriving yojson { strict = false }]
+  } [@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 type comm_info_reply =
   {
-    ci_comms : Yojson.Safe.t [@key "comms"];
-  } [@@deriving yojson { strict = false }]
+    ci_comms : Json.t [@key "comms"];
+  } [@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 (** {2 Kernel information} *)
 
@@ -145,9 +158,10 @@ type language_info =
     lang_mimetype : string [@key "mimetype"]; (** mimetype *)
     lang_file_ext : string [@key "file_extension"]; (** file extension *)
     lang_lexer : string option [@key "pygments_lexer"]; (** pygments lexer *)
-    lang_mode : Yojson.Safe.t [@key "codemirror_mode"]; (** codemirror mode *)
+    lang_mode : Json.t [@key "codemirror_mode"]; (** codemirror mode *)
     lang_exporter : string option [@key "nbconverter_exporter"];
-  } [@@deriving yojson { strict = false }]
+  } [@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 let language_info =
   {
@@ -164,7 +178,8 @@ type help_link =
   {
     help_text : string [@key "text"];
     help_url : string [@key "url"];
-  } [@@deriving yojson { strict = false }]
+  } [@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 let help_links =
   [
@@ -183,7 +198,8 @@ type kernel_info_reply =
     kernel_help_links : help_link list [@key "help_links"];
     kernel_lang_info : language_info [@key "language_info"];
     kernel_lang : string [@key "language"];
-  } [@@deriving yojson { strict = false }]
+  } [@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 let kernel_info_reply =
   let banner =
@@ -207,7 +223,8 @@ let kernel_info_reply =
 type shutdown =
   {
     shutdown_restart : bool [@key "restart"];
-  } [@@deriving yojson { strict = false }]
+  } [@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 (** {2 Request} *)
 
@@ -224,7 +241,7 @@ type request =
   | SHELL_COMM_OPEN of Comm.t [@name "comm_open"]
   | SHELL_COMM_MSG of Comm.t [@name "comm_msg"]
   | SHELL_COMM_CLOSE of Comm.t [@name "comm_close"]
-[@@deriving yojson { strict = false }]
+[@@deriving yojson]
 
 (** {2 Reply} *)
 
@@ -238,7 +255,7 @@ type reply =
   | SHELL_CONNECT_REP of connect_reply [@name "connect_reply"]
   | SHELL_COMM_INFO_REP of comm_info_reply [@name "comm_info_reply"]
   | SHELL_SHUTDOWN_REP of shutdown [@name "shutdown_reply"]
-[@@deriving yojson { strict = false }]
+[@@deriving yojson]
 
 let execute_reply ~count status =
   SHELL_EXEC_REP { exec_count = count; exec_status = status; }
diff --git a/jupyter/src/core/stdin.ml b/jupyter/src/core/stdin.ml
index 66b49cf1..dcf4c786 100644
--- a/jupyter/src/core/stdin.ml
+++ b/jupyter/src/core/stdin.ml
@@ -28,12 +28,14 @@ type input_request =
   {
     stdin_prompt : string [@key "prompt"];
     stdin_password : bool [@key "password"];
-  } [@@deriving yojson { strict = false }]
+  } [@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 type input_reply =
   {
     stdin_value : string [@key "value"];
-  } [@@deriving yojson { strict = false }]
+  } [@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 (** {2 Request} *)
 
diff --git a/jupyter/src/kernel/connection_info.ml b/jupyter/src/kernel/connection_info.ml
index 557f41f7..d47fff97 100644
--- a/jupyter/src/kernel/connection_info.ml
+++ b/jupyter/src/kernel/connection_info.ml
@@ -38,7 +38,8 @@ type t =
     key : string option [@default None];
     signature_scheme : string;
     transport : string;
-  } [@@deriving yojson { strict = false }]
+  } [@@deriving yojson]
+[@@yojson.allow_extra_fields]
 
 let from_file fname =
   if not (Sys.file_exists fname)
@@ -46,9 +47,8 @@ let from_file fname =
   let json = Yojson.Safe.from_file ~fname fname in
   info (fun pp -> pp "Load connection info: %s" (Yojson.Safe.to_string json)) ;
   match [%of_yojson: t] json with
-  | Result.Error msg -> Yojson.json_error msg
-  | Result.Ok info when info.key = Some "" -> { info with key = None }
-  | Result.Ok info -> info
+  | info when info.key = Some "" -> { info with key = None }
+  | info -> info
 
 (** [make_address info port] returns an address for ZeroMQ communication. *)
 let make_address info port =
diff --git a/jupyter/src/kernel/dune b/jupyter/src/kernel/dune
index 2a0e04f8..db6e7181 100644
--- a/jupyter/src/kernel/dune
+++ b/jupyter/src/kernel/dune
@@ -10,7 +10,7 @@
               Connection_info
               Hmac)
  (flags       ((:include %{workspace_root}/config/ocaml_flags.sexp)))
- (preprocess  (pps lwt_ppx ppx_deriving_yojson))
+ (preprocess  (pps lwt_ppx ppx_yojson_conv))
  (libraries   jupyter
               jupyter_repl
               jupyter_completor
@@ -21,4 +21,4 @@
               yojson
               zmq-lwt
               cryptokit
-              ppx_deriving_yojson.runtime))
+              ppx_yojson_conv_lib))
diff --git a/jupyter/src/kernel/message_channel.ml b/jupyter/src/kernel/message_channel.ml
index 55144e78..595cc8a5 100644
--- a/jupyter/src/kernel/message_channel.ml
+++ b/jupyter/src/kernel/message_channel.ml
@@ -76,8 +76,7 @@ struct
       let header = header_of_string header in
       let content = Yojson.Safe.from_string content
                     |> compose_content ~msg_type:header.msg_type
-                    |> [%of_yojson: Content.request]
-                    |> Jupyter.Json.or_die in
+                    |> [%of_yojson: Content.request] in
       {
         zmq_ids = ids;
         header;
@@ -99,7 +98,7 @@ struct
     let header = string_of_header resp.header in
     let parent_header = string_of_header_option resp.parent_header in
     let content =
-      match [%to_yojson: Content.reply] resp.content with
+      match [%yojson_of: Content.reply] resp.content with
       | `List (_ :: content :: _) -> Yojson.Safe.to_string content
       | _ -> "{}" in
     let hmac =
@@ -128,7 +127,7 @@ struct
 
   let reply ?time ~parent ch content =
     Jupyter.Message.create_next
-      ~content_to_yojson:[%to_yojson: Content.reply]
+      ~content_to_yojson:[%yojson_of: Content.reply]
       ?time parent content
     |> send ch
 
diff --git a/jupyter/bin/dune b/jupyter/src/main/dune
similarity index 72%
rename from jupyter/bin/dune
rename to jupyter/src/main/dune
index 056d28dc..36191f69 100644
--- a/jupyter/bin/dune
+++ b/jupyter/src/main/dune
@@ -3,11 +3,10 @@
  (modes       byte)
  (package     jupyter)
  (public_name ocaml-jupyter-kernel)
- (preprocess  (pps lwt_ppx ppx_deriving_yojson))
+ (preprocess  (pps lwt_ppx ppx_yojson_conv))
  (libraries   jupyter
               jupyter_log
               jupyter_repl
               jupyter_completor
-              jupyter_kernel
-              ppx_deriving.runtime)
+              jupyter_kernel)
  (flags       ((:include %{workspace_root}/config/ocaml_flags.sexp))))
diff --git a/jupyter/bin/jupyter_args.ml b/jupyter/src/main/jupyter_args.ml
similarity index 100%
rename from jupyter/bin/jupyter_args.ml
rename to jupyter/src/main/jupyter_args.ml
diff --git a/jupyter/bin/jupyter_args.mli b/jupyter/src/main/jupyter_args.mli
similarity index 100%
rename from jupyter/bin/jupyter_args.mli
rename to jupyter/src/main/jupyter_args.mli
diff --git a/jupyter/bin/jupyter_main.ml b/jupyter/src/main/jupyter_main.ml
similarity index 100%
rename from jupyter/bin/jupyter_main.ml
rename to jupyter/src/main/jupyter_main.ml
diff --git a/jupyter/src/notebook/dune b/jupyter/src/notebook/dune
index 3468e255..afd2c1a9 100644
--- a/jupyter/src/notebook/dune
+++ b/jupyter/src/notebook/dune
@@ -6,7 +6,7 @@
  (modules     Jupyter_notebook
               Unsafe)
  (flags       ((:include %{workspace_root}/config/ocaml_flags.sexp)))
- (preprocess  (pps ppx_deriving_yojson))
+ (preprocess  (pps ppx_yojson_conv))
  (libraries   jupyter
               uuidm
               base64
diff --git a/jupyter/src/notebook/unsafe.ml b/jupyter/src/notebook/unsafe.ml
index ebb73823..a967a7f4 100644
--- a/jupyter/src/notebook/unsafe.ml
+++ b/jupyter/src/notebook/unsafe.ml
@@ -52,5 +52,5 @@ let send_iopub ?ctx content =
   in
   let message =
     Jupyter.Message.create_next parent content
-      ~content_to_yojson:[%to_yojson: Jupyter.Iopub.reply] in
+      ~content_to_yojson:[%yojson_of: Jupyter.Iopub.reply] in
   send (Jupyter.Message.IOPUB_REP message)
diff --git a/jupyter/src/repl/lwt_async_rewrite.cppo.ml b/jupyter/src/repl/lwt_async_rewrite.cppo.ml
index a88fe8e2..21368ea5 100644
--- a/jupyter/src/repl/lwt_async_rewrite.cppo.ml
+++ b/jupyter/src/repl/lwt_async_rewrite.cppo.ml
@@ -21,16 +21,20 @@ type rewrite_rule = {
   (* Whether the rule is enabled or not. *)
 }
 
+let longident l = match Longident.unflatten l with
+  | Some li -> li
+  | None -> failwith "Failed to parse longident"
+
 let longident_lwt_main_run = Longident.Ldot (Longident.Lident "Lwt_main", "run")
 let longident_async_thread_safe_block_on_async_exn =
-  Longident.parse "Async.Thread_safe.block_on_async_exn"
+  longident ["Async"; "Thread_safe"; "block_on_async_exn"]
 
 let nolabel = Asttypes.Nolabel
 
 let rewrite_rules = [
   (* Rewrite Lwt.t expressions to Lwt_main.run <expr> *)
   {
-    type_to_rewrite = Longident.parse "Lwt.t";
+    type_to_rewrite = longident ["Lwt"; "t"];
     path_to_rewrite = None;
     required_values = [longident_lwt_main_run];
     rewrite = (fun loc e ->
@@ -45,7 +49,7 @@ let rewrite_rules = [
   (* Rewrite Async.Defered.t expressions to
      Async.Thread_safe.block_on_async_exn (fun () -> <expr>). *)
   {
-    type_to_rewrite = Longident.parse "Async.Deferred.t";
+    type_to_rewrite = longident ["Async"; "Deferred"; "t"];
     path_to_rewrite = None;
     required_values = [longident_async_thread_safe_block_on_async_exn];
     rewrite = (fun loc e ->
diff --git a/notebooks/word_description_from_DuckDuckGoAPI.ipynb b/notebooks/word_description_from_DuckDuckGoAPI.ipynb
index ca7ff322..fcc2d0ab 100644
--- a/notebooks/word_description_from_DuckDuckGoAPI.ipynb
+++ b/notebooks/word_description_from_DuckDuckGoAPI.ipynb
@@ -13,20 +13,24 @@
    "cell_type": "code",
    "execution_count": 1,
    "metadata": {
-    "collapsed": true,
     "scrolled": true
    },
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stderr",
+     "output_type": "stream",
+     "text": [
+     ]
+    }
+   ],
    "source": [
-    "#require \"cohttp,cohttp-lwt-unix,ppx_deriving_yojson\" ;;"
+    "#require \"cohttp,cohttp-lwt-unix,ppx_yojson_conv\" ;;"
    ]
   },
   {
    "cell_type": "code",
    "execution_count": 2,
-   "metadata": {
-    "collapsed": true
-   },
+   "metadata": {},
    "outputs": [],
    "source": [
     "open Lwt.Infix ;;"
@@ -41,9 +45,8 @@
      "data": {
       "text/plain": [
        "type t = { definition : string; abstract : string; }\n",
-       "val to_yojson : t -> Yojson.Safe.json = <fun>\n",
-       "val of_yojson : Yojson.Safe.json -> t Ppx_deriving_yojson_runtime.error_or =\n",
-       "  <fun>\n"
+       "val t_of_yojson : Ppx_yojson_conv_lib.Yojson.Safe.t -> t = <fun>\n",
+       "val yojson_of_t : t -> Ppx_yojson_conv_lib.Yojson.Safe.t = <fun>\n"
       ]
      },
      "execution_count": 3,
@@ -55,7 +58,7 @@
     "type t = {\n",
     "    definition : string [@key \"Definition\"];\n",
     "    abstract : string [@key \"Abstract\"];\n",
-    "  } [@@deriving yojson { strict = false }]"
+    "  } [@@deriving yojson] [@@yojson.allow_extra_fields]"
    ]
   },
   {
@@ -80,7 +83,7 @@
       "text/plain": [
        "val body : string option =\n",
        "  Some\n",
-       "   \"OCaml, originally named Objective Caml, is the main implementation of the programming language Caml, created by Xavier Leroy, J\\195\\169r\\195\\180me Vouillon, Damien Doligez, Didier R\\195\\169my, Asc\\195\\161nder Su\\195\\161rez and others in 1996. A member of the ML language family, OCaml extends the core Caml language with object-oriented programming constructs.\"\n"
+       "   \"OCaml is a general-purpose, multi-paradigm programming language which extends the Caml dialect of ML with object-oriented features. OCaml was created in 1996 by Xavier Leroy, Jérôme Vouillon, Damien Doligez, Didier Rémy, Ascánder Suárez, and others. The OCaml toolchain includes an interactive\"... (* string length 994; truncated *)\n"
       ]
      },
      "execution_count": 4,
@@ -96,14 +99,13 @@
     "    let uri = Uri.add_query_param base_uri (\"q\", [query]) in\n",
     "    Cohttp_lwt_unix.Client.get uri >>= fun (resp, body) -> (* GET contents from a given uri *)\n",
     "    assert (Cohttp.Response.status resp = `OK) ; (* Check HTTP response code *)\n",
-    "    Cohttp_lwt_body.to_string body >|= fun body -> (* Receive contents *)\n",
+    "    Cohttp_lwt.Body.to_string body >|= fun body -> (* Receive contents *)\n",
     "    Yojson.Safe.from_string body\n",
     "    |> [%of_yojson: t]\n",
     "    |> function\n",
-    "    | Result.Ok { definition = \"\"; abstract = \"\"; } -> None\n",
-    "    | Result.Ok { definition = \"\"; abstract; } -> Some abstract\n",
-    "    | Result.Ok { definition; abstract = \"\"; } -> Some definition\n",
-    "    | _ -> failwith \"Oops!\"\n",
+    "    | { definition = \"\"; abstract = \"\"; } -> None\n",
+    "    | { definition = \"\"; abstract; } -> Some abstract\n",
+    "    | { definition; _ } -> Some definition\n",
     "  end"
    ]
   },
@@ -119,7 +121,7 @@
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": "OCaml 4.04.2",
+   "display_name": "OCaml 4.12.0",
    "language": "OCaml",
    "name": "ocaml-jupyter"
   },
@@ -130,7 +132,7 @@
    "name": "OCaml",
    "nbconverter_exporter": null,
    "pygments_lexer": "OCaml",
-   "version": "4.04.2"
+   "version": "4.12.0"
   }
  },
  "nbformat": 4,
diff --git a/test/completor/dune b/test/completor/dune
index 1c484acb..6f124a86 100644
--- a/test/completor/dune
+++ b/test/completor/dune
@@ -1,10 +1,9 @@
 (executables
  (names      test_completor)
- (preprocess (pps lwt_ppx ppx_deriving.show ppx_deriving_yojson))
+ (preprocess (pps lwt_ppx ppx_deriving.show ppx_yojson_conv))
  (libraries  jupyter
              jupyter_completor
-             ounit2
-             ppx_deriving.runtime)
+             ounit2)
  (flags      ((:include %{workspace_root}/config/ocaml_flags.sexp)
               (:include %{workspace_root}/config/ocaml_test_flags.sexp))))
 
diff --git a/test/completor/test_merlin.ml b/test/completor/test_merlin.ml
index 7cf06dfa..85eb379b 100644
--- a/test/completor/test_merlin.ml
+++ b/test/completor/test_merlin.ml
@@ -28,7 +28,7 @@ open Jupyter_completor
 (** {2 Merlin.occurrences} *)
 
 let pp_ident_reply ppf reply =
-  [%to_yojson: Merlin.ident_reply] reply
+  [%yojson_of: Merlin.ident_reply] reply
   |> Yojson.Safe.to_string
   |> pp_print_string ppf
 
@@ -81,7 +81,7 @@ let test_abs_position ctxt =
 (** {2 Merlin.complete} *)
 
 let pp_reply ppf reply =
-  [%to_yojson: Merlin.reply] reply
+  [%yojson_of: Merlin.reply] reply
   |> Yojson.Safe.to_string
   |> fprintf ppf "%s"
 
diff --git a/test/integration/dune b/test/integration/dune
index 5b4aca42..cfe9b34b 100644
--- a/test/integration/dune
+++ b/test/integration/dune
@@ -3,9 +3,11 @@
 
 (executables
  (names      runtest)
- (preprocess (pps ppx_deriving_yojson))
+ (preprocess (pps ppx_yojson_conv ppx_yojson_conv))
+ (flags      (:standard
+              -w A-4-31-33-34-39-41-42-43-44-45-48-49-50-58
+              -safe-string -strict-sequence -strict-formats
+              -short-paths))
  (libraries  jupyter
              unix
-             ppx_deriving.runtime)
- (flags      ((:include %{workspace_root}/config/ocaml_flags.sexp)
-              (:include %{workspace_root}/config/ocaml_test_flags.sexp))))
+             ppx_yojson_conv_lib))
diff --git a/test/integration/runtest.ml b/test/integration/runtest.ml
index e018fe03..359b7946 100644
--- a/test/integration/runtest.ml
+++ b/test/integration/runtest.ml
@@ -29,7 +29,7 @@ type cell =
     execution_count : int;
     source : string list;
     outputs : string list;
-    metadata : Yojson.Safe.t;
+    metadata : Json.t;
   }
 [@@deriving yojson]
 
@@ -90,7 +90,7 @@ let runtest ml_fname =
   let ipynb_fname = ml_fname ^ ".ipynb" in
   read_lines ml_fname
   |> ipynb_of_code
-  |> [%to_yojson: ipynb]
+  |> [%yojson_of: ipynb]
   |> Yojson.Safe.to_file ipynb_fname ;
   let cmd = sprintf "jupyter nbconvert --to notebook --execute %S" ipynb_fname in
   printf "%s>> %s%s@." AnsiCode.FG.cyan cmd AnsiCode.reset ;
diff --git a/test/integration/suite/ppx.ml b/test/integration/suite/ppx.ml
index 9513f9d9..b64ff809 100644
--- a/test/integration/suite/ppx.ml
+++ b/test/integration/suite/ppx.ml
@@ -1,4 +1,4 @@
-#require "ppx_deriving_yojson" ;;
+#require "ppx_yojson_conv" ;;
 
 type t = { foo : int; baz : string; } [@@deriving yojson]
 
@@ -6,7 +6,7 @@ let expected = "{\"foo\":42,\"baz\":\"hello\"}"
 
 let actual =
   { foo = 42; baz = "hello"; }
-  |> [%to_yojson: t]
+  |> [%yojson_of: t]
   |> Yojson.Safe.to_string
 
 let () = assert (expected = actual)
diff --git a/test/kernel/dune b/test/kernel/dune
index 3524db12..719b6fa6 100644
--- a/test/kernel/dune
+++ b/test/kernel/dune
@@ -1,11 +1,10 @@
 (executables
  (names      test_kernel)
  (modes      byte)
- (preprocess (pps lwt_ppx ppx_deriving.show ppx_deriving_yojson))
+ (preprocess (pps lwt_ppx ppx_deriving.show ppx_yojson_conv))
  (libraries  jupyter
              jupyter_kernel
-             ounit2
-             ppx_deriving.runtime)
+             ounit2)
  (flags      ((:include %{workspace_root}/config/ocaml_flags.sexp)
               (:include %{workspace_root}/config/ocaml_test_flags.sexp))))
 
diff --git a/test/kernel/test_message_channel.ml b/test/kernel/test_message_channel.ml
index da31849b..55d56949 100644
--- a/test/kernel/test_message_channel.ml
+++ b/test/kernel/test_message_channel.ml
@@ -53,7 +53,7 @@ let test_recv ctxt =
   let channel = Channel.create ~key ~ctx ~kind:Zmq.Socket.rep "" in
   let actual = Lwt_main.run @@ Channel.recv channel in
   assert_equal ~ctxt ~printer:(fun msg ->
-      [%to_yojson: Jupyter.Shell.request Jupyter.Message.t] msg
+      [%yojson_of: Jupyter.Shell.request Jupyter.Message.t] msg
       |> Yojson.Safe.to_string)
     message actual
 
diff --git a/test/repl/dune b/test/repl/dune
index 0f529fde..ec4d809d 100644
--- a/test/repl/dune
+++ b/test/repl/dune
@@ -2,11 +2,10 @@
  (names      test_evaluation
              test_process)
  (modes      byte)
- (preprocess (pps lwt_ppx ppx_deriving.show ppx_deriving_yojson))
+ (preprocess (pps lwt_ppx ppx_deriving.show ppx_yojson_conv))
  (libraries  jupyter
              jupyter_repl
-             ounit2
-             ppx_deriving.runtime)
+             ounit2)
  (flags      ((:include %{workspace_root}/config/ocaml_flags.sexp)
               (:include %{workspace_root}/config/ocaml_test_flags.sexp))))
 
diff --git a/test/repl/test_evaluation.ml b/test/repl/test_evaluation.ml
index 6a7dc1c0..6b466dab 100644
--- a/test/repl/test_evaluation.ml
+++ b/test/repl/test_evaluation.ml
@@ -27,12 +27,12 @@ open Jupyter.Shell
 open Jupyter_repl.Evaluation
 
 let pp_status ppf status =
-  [%to_yojson: Jupyter.Shell.status] status
+  [%yojson_of: Jupyter.Shell.status] status
   |> Yojson.Safe.to_string
   |> pp_print_string ppf
 
 let pp_reply ppf reply =
-  [%to_yojson: Jupyter.Iopub.reply] reply
+  [%yojson_of: Jupyter.Iopub.reply] reply
   |> Yojson.Safe.to_string
   |> pp_print_string ppf
 
diff --git a/test/repl/test_process.ml b/test/repl/test_process.ml
index b319d2ef..319135cd 100644
--- a/test/repl/test_process.ml
+++ b/test/repl/test_process.ml
@@ -36,9 +36,9 @@ type reply =
 let pp_reply ppf reply =
   begin
     match reply with
-    | Shell shell -> [%to_yojson: Jupyter.Shell.reply] shell
-    | Iopub iopub -> [%to_yojson: Jupyter.Iopub.reply] iopub
-    | Stdin stdin -> [%to_yojson: Jupyter.Stdin.reply] stdin
+    | Shell shell -> [%yojson_of: Jupyter.Shell.reply] shell
+    | Iopub iopub -> [%yojson_of: Jupyter.Iopub.reply] iopub
+    | Stdin stdin -> [%yojson_of: Jupyter.Stdin.reply] stdin
   end
   |> Yojson.Safe.to_string
   |> pp_print_string ppf