diff --git a/gitlab-pages/docs/reference/bytes.md b/gitlab-pages/docs/reference/bytes.md
new file mode 100644
index 000000000..3a3349550
--- /dev/null
+++ b/gitlab-pages/docs/reference/bytes.md
@@ -0,0 +1,128 @@
+---
+id: bytes-reference
+title: Bytes
+---
+
+## Bytes.concat(b1: bytes, b2: bytes) : bytes
+
+Concatenate together two `bytes` arguments and return the result.
+
+<!--DOCUSAURUS_CODE_TABS-->
+
+<!--PascaLIGO-->
+
+```pascaligo
+function concat_op (const s : bytes) : bytes is
+  begin skip end with bytes_concat(s , 0x7070)
+```
+
+<!--CameLIGO-->
+
+```cameligo
+let concat_op (s : bytes) : bytes =
+   Bytes.concat s 0x7070
+```
+
+<!--ReasonLIGO-->
+
+```reasonligo
+let concat_op = (s: bytes): bytes => Bytes.concat(s, 0x7070);
+```
+
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+## Bytes.slice(pos1: nat, pos2: nat, data: bytes) : bytes
+
+Extract the bytes between `pos1` and `pos2`. **Positions are zero indexed and
+inclusive**. For example if you gave the input "ff7a7aff" to the following:
+
+<!--DOCUSAURUS_CODE_TABS-->
+
+<!--PascaLIGO-->
+
+```pascaligo
+function slice_op (const s : bytes) : bytes is
+  begin skip end with bytes_slice(1n , 2n , s)
+```
+
+<!--CameLIGO-->
+
+```cameligo
+let slice_op (s : bytes) : bytes =
+   Bytes.slice 1n 2n s
+```
+
+<!--ReasonLIGO-->
+
+```
+let slice_op = (s: bytes): bytes => Bytes.slice(1n, 2n, s);
+```
+
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+It would return "7a7a" rather than "ff7a" or "ff" or "7a".
+
+## Bytes.pack(data: a') : bytes
+
+Converts Michelson data structures to a binary format for serialization.
+
+> ⚠️ `PACK` and `UNPACK` are features of Michelson that are intended to be used by people that really know what they're doing. There are several failure cases (such as `UNPACK`ing a lambda from an untrusted source), most of which are beyond the scope of this document. Don't use these functions without doing your homework first.
+
+<!--DOCUSAURUS_CODE_TABS-->
+
+<!--PascaLIGO-->
+```pascaligo
+function id_string (const p : string) : option(string) is block {
+  const packed : bytes = bytes_pack(p) ;
+} with (bytes_unpack(packed): option(string))
+```
+
+<!--CameLIGO-->
+```cameligo
+let id_string (p: string) : string option =
+  let packed: bytes = Bytes.pack p in
+  ((Bytes.unpack packed): string option)
+```
+
+<!--ReasonLIGO-->
+```reasonligo
+let id_string = (p: string) : option(string) => {
+  let packed : bytes = Bytes.pack(p);
+  ((Bytes.unpack(packed)): option(string));
+};
+```
+
+<!--END_DOCUSAURUS_CODE_TABS-->
+
+## Bytes.unpack(packed: bytes) : a'
+
+Reverses the result of using `unpack` on data, going from Michelson's binary
+serialization format to the `option` type annotated on the call.
+
+> ⚠️ `PACK` and `UNPACK` are features of Michelson that are intended to be used by people that really know what they're doing. There are several failure cases (such as `UNPACK`ing a lambda from an untrusted source), most of which are beyond the scope of this document. Don't use these functions without doing your homework first.
+
+<!--DOCUSAURUS_CODE_TABS-->
+
+<!--PascaLIGO-->
+```pascaligo
+function id_string (const p : string) : option(string) is block {
+  const packed : bytes = bytes_pack(p) ;
+} with (bytes_unpack(packed): option(string))
+```
+
+<!--CameLIGO-->
+```cameligo
+let id_string (p: string) : string option =
+  let packed: bytes = Bytes.pack p in
+  ((Bytes.unpack packed): string option)
+```
+
+<!--ReasonLIGO-->
+```reasonligo
+let id_string = (p: string) : option(string) => {
+  let packed : bytes = Bytes.pack(p);
+  ((Bytes.unpack(packed)): option(string));
+};
+```
+
+<!--END_DOCUSAURUS_CODE_TABS-->
diff --git a/src/test/integration_tests.ml b/src/test/integration_tests.ml
index 58b492fc2..720f03b0f 100644
--- a/src/test/integration_tests.ml
+++ b/src/test/integration_tests.ml
@@ -414,7 +414,7 @@ let bytes_arithmetic () : unit result =
   let%bind foototo = e_bytes_hex "0f007070" in
   let%bind toto = e_bytes_hex "7070" in
   let%bind empty = e_bytes_hex "" in
-  let%bind tata = e_bytes_hex "7a7a7a7a" in
+  let%bind tata = e_bytes_hex "ff7a7aff" in
   let%bind at = e_bytes_hex "7a7a" in
   let%bind ba = e_bytes_hex "ba" in
   let%bind () = expect_eq program "concat_op" foo foototo in
@@ -476,7 +476,7 @@ let bytes_arithmetic_mligo () : unit result =
   let%bind foototo = e_bytes_hex "0f007070" in
   let%bind toto = e_bytes_hex "7070" in
   let%bind empty = e_bytes_hex "" in
-  let%bind tata = e_bytes_hex "7a7a7a7a" in
+  let%bind tata = e_bytes_hex "ff7a7aff" in
   let%bind at = e_bytes_hex "7a7a" in
   let%bind ba = e_bytes_hex "ba" in
   let%bind () = expect_eq program "concat_op" foo foototo in
@@ -496,7 +496,7 @@ let bytes_arithmetic_religo () : unit result =
   let%bind foototo = e_bytes_hex "0f007070" in
   let%bind toto = e_bytes_hex "7070" in
   let%bind empty = e_bytes_hex "" in
-  let%bind tata = e_bytes_hex "7a7a7a7a" in
+  let%bind tata = e_bytes_hex "ff7a7aff" in
   let%bind at = e_bytes_hex "7a7a" in
   let%bind ba = e_bytes_hex "ba" in
   let%bind () = expect_eq program "concat_op" foo foototo in