diff --git a/atd/src/annot.ml b/atd/src/annot.ml
index bd94be71..4c4c9df0 100644
--- a/atd/src/annot.ml
+++ b/atd/src/annot.ml
@@ -214,3 +214,16 @@ let validate schema root =
   List.iter (fun sec ->
     validate_section sec root
   ) schema
+
+let filter_by_tags ~tags full_module =
+  let aux (annot : t) =
+    annot |> List.filter (fun (section, _) -> (
+      match fields annot ~section ~field:"tag" with
+      | [] -> true
+      | fields ->
+          fields
+          |> List.filter_map snd 
+          |> List.exists (fun value -> List.mem value tags)
+    ))
+  in
+  Ast.map_all_annot aux full_module
diff --git a/atd/src/annot.mli b/atd/src/annot.mli
index 690a7b7a..01f685ce 100644
--- a/atd/src/annot.mli
+++ b/atd/src/annot.mli
@@ -203,3 +203,10 @@ type schema = schema_section list
 (** Check that annotations of interest are not misplaced.
     Raises an exception with an error message when the check fails. *)
 val validate : schema -> Ast.any -> unit
+
+(**
+   Remove annotations which do not have at least one of the provided [tags] found in their tag field.
+*)
+val filter_by_tags :
+  tags : string list ->
+  Ast.full_module -> Ast.full_module
diff --git a/atd/src/json.ml b/atd/src/json.ml
index 37abb3aa..a11e778f 100644
--- a/atd/src/json.ml
+++ b/atd/src/json.ml
@@ -90,6 +90,12 @@ let annot_schema_json : Annot.schema = [
       Variant, "name";
       Field, "name";
       Field, "tag_field";
+      Module_head, "tag";
+      Type_def, "tag";
+      Type_expr, "tag";
+      Variant, "tag";
+      Cell, "tag";
+      Field, "tag";
     ]
   };
   {
diff --git a/atd/src/util.ml b/atd/src/util.ml
index cd186d12..9adbad44 100644
--- a/atd/src/util.ml
+++ b/atd/src/util.ml
@@ -8,6 +8,7 @@ let read_lexbuf
     ?(inherit_variants = false)
     ?(pos_fname = "")
     ?(pos_lnum = 1)
+    ~tags
     lexbuf =
 
   Lexer.init_fname lexbuf pos_fname pos_lnum;
@@ -30,12 +31,16 @@ let read_lexbuf
    | Some schema ->
        Annot.validate schema (Ast.Full_module full_module)
   );
+  let full_module = match tags with 
+    | [] -> full_module 
+    | tags -> Annot.filter_by_tags ~tags full_module
+  in
   (full_module, original_types)
 
 let read_channel
     ?annot_schema ?expand ?keep_builtins ?keep_poly ?xdebug
     ?inherit_fields ?inherit_variants
-    ?pos_fname ?pos_lnum
+    ?pos_fname ?pos_lnum ~tags
     ic =
   let lexbuf = Lexing.from_channel ic in
   let pos_fname =
@@ -45,12 +50,12 @@ let read_channel
       pos_fname
   in
   read_lexbuf ?annot_schema ?expand ?keep_builtins ?keep_poly ?xdebug
-    ?inherit_fields ?inherit_variants ?pos_fname ?pos_lnum lexbuf
+    ?inherit_fields ?inherit_variants ?pos_fname ?pos_lnum ~tags lexbuf
 
 let load_file
     ?annot_schema ?expand ?keep_builtins ?keep_poly ?xdebug
     ?inherit_fields ?inherit_variants
-    ?pos_fname ?pos_lnum
+    ?pos_fname ?pos_lnum ~tags
     file =
   let ic = open_in file in
   let finally () = close_in_noerr ic in
@@ -63,7 +68,7 @@ let load_file
     let ast =
       read_channel
         ?annot_schema ?expand ?keep_builtins ?keep_poly ?xdebug
-        ?inherit_fields ?inherit_variants ?pos_fname ?pos_lnum ic
+        ?inherit_fields ?inherit_variants ?pos_fname ?pos_lnum ~tags ic
     in
     finally ();
     ast
@@ -74,11 +79,11 @@ let load_file
 let load_string
     ?annot_schema ?expand ?keep_builtins ?keep_poly ?xdebug
     ?inherit_fields ?inherit_variants
-    ?pos_fname ?pos_lnum
+    ?pos_fname ?pos_lnum ~tags
     s =
   let lexbuf = Lexing.from_string s in
   read_lexbuf ?annot_schema ?expand ?keep_builtins ?keep_poly ?xdebug
-    ?inherit_fields ?inherit_variants ?pos_fname ?pos_lnum lexbuf
+    ?inherit_fields ?inherit_variants ?pos_fname ?pos_lnum ~tags lexbuf
 
 module Tsort = Sort.Make (
   struct
diff --git a/atd/src/util.mli b/atd/src/util.mli
index aeb0e258..0d5d92fb 100644
--- a/atd/src/util.mli
+++ b/atd/src/util.mli
@@ -10,6 +10,7 @@ val read_lexbuf :
   ?inherit_variants:bool ->
   ?pos_fname:string ->
   ?pos_lnum:int ->
+  tags:string list ->
   Lexing.lexbuf -> Ast.full_module * Expand.original_types
   (** Read an ATD file from a lexbuf. See also [read_channel], [load_file]
       and [load_string].
@@ -66,6 +67,7 @@ val read_channel :
   ?inherit_variants:bool ->
   ?pos_fname:string ->
   ?pos_lnum:int ->
+  tags:string list ->
   in_channel -> Ast.full_module * Expand.original_types
   (** Read an ATD file from an [in_channel]. Options: see [read_lexbuf].
       The default [pos_fname] is set to ["<stdin>"] when appropriate. *)
@@ -80,6 +82,7 @@ val load_file :
   ?inherit_variants:bool ->
   ?pos_fname:string ->
   ?pos_lnum:int ->
+  tags:string list ->
   string -> Ast.full_module * Expand.original_types
   (** Read an ATD file. Options: see [read_lexbuf].
       The default [pos_fname] is the given input file name. *)
@@ -94,6 +97,7 @@ val load_string :
   ?inherit_variants:bool ->
   ?pos_fname:string ->
   ?pos_lnum:int ->
+  tags:string list ->
   string -> Ast.full_module * Expand.original_types
   (** Read ATD data from a string. Options: see [read_lexbuf]. *)
 
diff --git a/atd/test/annot.ml b/atd/test/annot.ml
index d830ba3e..3cd816c9 100644
--- a/atd/test/annot.ml
+++ b/atd/test/annot.ml
@@ -31,11 +31,11 @@ let schema : Atd.Annot.schema = [
 ]
 
 let test_valid_input atd_input =
-  let root, _orig_types = Atd.Util.load_string atd_input in
+  let root, _orig_types = Atd.Util.load_string ~tags:[] atd_input in
   Atd.Annot.validate schema (Atd.Ast.Full_module root)
 
 let test_invalid_input atd_input =
-  let root, _orig_types = Atd.Util.load_string atd_input in
+  let root, _orig_types = Atd.Util.load_string ~tags:[] atd_input in
   try
     Atd.Annot.validate schema (Atd.Ast.Full_module root);
     assert false
diff --git a/atdcat/src/atdcat.ml b/atdcat/src/atdcat.ml
index 228478cb..2b02655c 100644
--- a/atdcat/src/atdcat.ml
+++ b/atdcat/src/atdcat.ml
@@ -78,7 +78,7 @@ let parse
       fun file ->
         let m, _orig_defs =
           Atd.Util.load_file ~annot_schema ~expand ~keep_poly ~xdebug
-            ~inherit_fields ~inherit_variants file
+            ~inherit_fields ~inherit_variants ~tags:[] file
         in
         if remove_wraps then
           Atd.Ast.remove_wrap_constructs m
diff --git a/atdcpp/src/bin/Atdcpp_main.ml b/atdcpp/src/bin/Atdcpp_main.ml
index 2457fb32..15dfdcdd 100644
--- a/atdcpp/src/bin/Atdcpp_main.ml
+++ b/atdcpp/src/bin/Atdcpp_main.ml
@@ -7,6 +7,7 @@ open Cmdliner
 
 type conf = {
   input_files: string list;
+  tags: string list;
   version: bool;
 }
 
@@ -18,7 +19,7 @@ let run conf =
   else
     conf.input_files
     |> List.iter (fun atd_file ->
-      Atdcpp.Codegen.run_file atd_file
+      Atdcpp.Codegen.run_file ~tags:conf.tags atd_file
     )
 
 (***************************************************************************)
@@ -38,6 +39,13 @@ let input_files_term =
   let default = [] in
   Arg.value (Arg.pos_all Arg.file default info)
 
+let tags_term =
+  let info =
+    Arg.info ["tag"]
+      ~doc:"Only evaluate annotations which have either the provided TAG as a field value <... tag=TAG>, or have no tags specified.\nOption can be used multiple times to specify several tags"
+  in
+  Arg.value (Arg.opt_all Arg.string [] info)
+
 let version_term =
   let info =
     Arg.info ["version"]
@@ -94,14 +102,16 @@ type bar = [
 ]
 
 let cmdline_term run =
-  let combine input_files version =
+  let combine input_files tags version =
     run {
       input_files;
       version;
+      tags;
     }
   in
   Term.(const combine
         $ input_files_term
+        $ tags_term
         $ version_term
        )
 
diff --git a/atdcpp/src/lib/Codegen.ml b/atdcpp/src/lib/Codegen.ml
index 874460eb..31b864d2 100644
--- a/atdcpp/src/lib/Codegen.ml
+++ b/atdcpp/src/lib/Codegen.ml
@@ -34,6 +34,12 @@ let annot_schema_cpp : Atd.Annot.schema_section =
       Field, "default";
       Module_head, "include";
       Module_head, "namespace";
+      Module_head, "tag";
+      Type_def, "tag";
+      Type_expr, "tag";
+      Variant, "tag";
+      Cell, "tag";
+      Field, "tag";
     ]
   }
 
@@ -1576,7 +1582,7 @@ let to_cpp_file ~atd_filename (items : A.module_body) dst_path namespace_name =
   |> double_spaced
   |> Indent.to_file ~indent:4 dst_path
 
-let run_file src_path =
+let run_file ~tags src_path =
   let src_name = Filename.basename src_path in
   let dst_name =
     (if Filename.check_suffix src_name ".atd" then
@@ -1594,6 +1600,7 @@ let run_file src_path =
       ~keep_builtins:true
       ~inherit_fields:true
       ~inherit_variants:true
+      ~tags
       src_path
   in
   let full_module = Atd.Ast.use_only_specific_variants full_module in
diff --git a/atdcpp/src/lib/Codegen.mli b/atdcpp/src/lib/Codegen.mli
index fc58e255..c0e4286e 100644
--- a/atdcpp/src/lib/Codegen.mli
+++ b/atdcpp/src/lib/Codegen.mli
@@ -4,4 +4,4 @@
 
 (** Take ATD type definitions and translate them to C++, writing
     them out to a file which should have the '.d' extension. *)
-val run_file : string -> unit
+val run_file : tags:string list -> string -> unit
diff --git a/atdd/src/bin/Atdd_main.ml b/atdd/src/bin/Atdd_main.ml
index da4576e2..efcfae9c 100644
--- a/atdd/src/bin/Atdd_main.ml
+++ b/atdd/src/bin/Atdd_main.ml
@@ -7,6 +7,7 @@ open Cmdliner
 
 type conf = {
   input_files: string list;
+  tags: string list;
   version: bool;
 }
 
@@ -18,7 +19,7 @@ let run conf =
   else
     conf.input_files
     |> List.iter (fun atd_file ->
-      Atdd.Codegen.run_file atd_file
+      Atdd.Codegen.run_file ~tags:conf.tags atd_file
     )
 
 (***************************************************************************)
@@ -38,6 +39,13 @@ let input_files_term =
   let default = [] in
   Arg.value (Arg.pos_all Arg.file default info)
 
+let tags_term =
+  let info =
+    Arg.info ["tag"]
+      ~doc:"Only evaluate annotations which have either the provided TAG as a field value <... tag=TAG>, or have no tags specified.\nOption can be used multiple times to specify several tags"
+  in
+  Arg.value (Arg.opt_all Arg.string [] info)
+
 let version_term =
   let info =
     Arg.info ["version"]
@@ -94,14 +102,16 @@ type bar = [
 ]
 
 let cmdline_term run =
-  let combine input_files version =
+  let combine input_files tags version =
     run {
       input_files;
       version;
+      tags;
     }
   in
   Term.(const combine
         $ input_files_term
+        $ tags_term
         $ version_term
        )
 
diff --git a/atdd/src/lib/Codegen.ml b/atdd/src/lib/Codegen.ml
index 491d8b61..9e65ff26 100644
--- a/atdd/src/lib/Codegen.ml
+++ b/atdd/src/lib/Codegen.ml
@@ -32,6 +32,12 @@ let annot_schema_dlang : Atd.Annot.schema_section =
       Type_expr, "wrap";
       Field, "default";
       Module_head, "import";
+      Module_head, "tag";
+      Type_def, "tag";
+      Type_expr, "tag";
+      Variant, "tag";
+      Cell, "tag";
+      Field, "tag";
     ]
   }
 
@@ -1126,7 +1132,7 @@ let to_file ~atd_filename ~head (items : A.module_body) dst_path =
   |> double_spaced
   |> Indent.to_file ~indent:4 dst_path
 
-let run_file src_path =
+let run_file ~tags src_path =
   let src_name = Filename.basename src_path in
   let dst_name =
     (if Filename.check_suffix src_name ".atd" then
@@ -1143,6 +1149,7 @@ let run_file src_path =
       ~keep_builtins:true
       ~inherit_fields:true
       ~inherit_variants:true
+      ~tags
       src_path
   in
   let full_module = Atd.Ast.use_only_specific_variants full_module in
diff --git a/atdd/src/lib/Codegen.mli b/atdd/src/lib/Codegen.mli
index 180fb5ef..67e93fdd 100644
--- a/atdd/src/lib/Codegen.mli
+++ b/atdd/src/lib/Codegen.mli
@@ -4,4 +4,4 @@
 
 (** Take ATD type definitions and translate them to Dlang, writing
     them out to a file which should have the '.d' extension. *)
-val run_file : string -> unit
+val run_file : tags:string list -> string -> unit
diff --git a/atddiff/src/lib/Atddiff.ml b/atddiff/src/lib/Atddiff.ml
index 97eb4113..7e8db203 100644
--- a/atddiff/src/lib/Atddiff.ml
+++ b/atddiff/src/lib/Atddiff.ml
@@ -52,6 +52,7 @@ let compare_files
     |> Atd.Util.load_file
       ~inherit_fields:true (* simplifies comparison *)
       ~inherit_variants:true (* simplifies comparison *)
+      ~tags:[]
     |> fst
     |> Atd.Ast.remove_wrap_constructs
   in
diff --git a/atdgen/bin/ag_main.ml b/atdgen/bin/ag_main.ml
index 906025ed..755df866 100644
--- a/atdgen/bin/ag_main.ml
+++ b/atdgen/bin/ag_main.ml
@@ -71,6 +71,10 @@ let main () =
     let l = Re.Str.split (Re.Str.regexp " *, *\\| +") s in
     opens := List.rev_append l !opens
   in
+  let tags = ref [] in
+  let add_tags t =
+    tags := List.rev_append t !tags
+  in
   let pp_convs : Ocaml.pp_convs ref = ref (Ocaml.Ppx_deriving []) in
   let set_pp_convs arg =
     match !pp_convs with
@@ -104,6 +108,14 @@ let main () =
          Insert '[@@ATTR]' after OCaml type definitions.
          Option can be used multiple times to specify several attributes
     ";
+    "-tag", Arg.String (fun s -> add_tags [ s ]),
+    "
+    TAG
+         Only evaluate annotations which have either 
+          - the provided TAG as a field value <... tag=TAG>,
+          - or have no tags specified.
+         Option can be used multiple times to specify several tags
+    ";
     "-t", Arg.Unit (fun () ->
                       set_once "output type" mode T;
                       set_once "no function definitions" with_fundefs false),
@@ -422,6 +434,7 @@ Recommended usage: %s (-t|-b|-j|-v|-dep|-list|-mel) example.atd" Sys.argv.(0) in
           ~type_aliases
           ~force_defaults
           ~ocaml_version
+          ~tags:!tags
           atd_file ocaml_prefix
 
 let () =
diff --git a/atdgen/src/biniou.ml b/atdgen/src/biniou.ml
index ce554c24..565b3146 100644
--- a/atdgen/src/biniou.ml
+++ b/atdgen/src/biniou.ml
@@ -41,6 +41,12 @@ let annot_schema_biniou : Atd.Annot.schema = [
     section = "biniou";
     fields = [
       Type_expr, "repr";
+      Module_head, "tag";
+      Type_def, "tag";
+      Type_expr, "tag";
+      Variant, "tag";
+      Cell, "tag";
+      Field, "tag";
     ]
   };
   {
@@ -50,6 +56,12 @@ let annot_schema_biniou : Atd.Annot.schema = [
       Type_def, "module";
       Type_def, "predef";
       Type_def, "t";
+      Module_head, "tag";
+      Type_def, "tag";
+      Type_expr, "tag";
+      Variant, "tag";
+      Cell, "tag";
+      Field, "tag";
     ]
   };
 ]
diff --git a/atdgen/src/ob_emit.ml b/atdgen/src/ob_emit.ml
index ed68b823..66f5373c 100644
--- a/atdgen/src/ob_emit.ml
+++ b/atdgen/src/ob_emit.ml
@@ -1357,6 +1357,7 @@ let make_ocaml_files
     ~force_defaults:_
     ~ocaml_version
     ~pp_convs
+    ~tags
     atd_file out =
   let ((head, m0), _) =
     match atd_file with
@@ -1364,13 +1365,13 @@ let make_ocaml_files
         Atd.Util.load_file
           ~annot_schema
           ~expand:false ~inherit_fields:true ~inherit_variants:true
-          ?pos_fname ?pos_lnum
+          ?pos_fname ?pos_lnum ~tags
           file
     | None ->
         Atd.Util.read_channel
           ~annot_schema
           ~expand:false ~inherit_fields:true ~inherit_variants:true
-          ?pos_fname ?pos_lnum
+          ?pos_fname ?pos_lnum ~tags
           stdin
   in
   let tsort =
diff --git a/atdgen/src/ob_emit.mli b/atdgen/src/ob_emit.mli
index eabcd213..3ccce659 100644
--- a/atdgen/src/ob_emit.mli
+++ b/atdgen/src/ob_emit.mli
@@ -12,4 +12,5 @@ val make_ocaml_files
   -> force_defaults:_ (* not used *)
   -> ocaml_version:(int * int) option
   -> pp_convs:Ocaml.pp_convs
+  -> tags:string list
   -> string option -> Ox_emit.target -> unit
diff --git a/atdgen/src/ocaml.ml b/atdgen/src/ocaml.ml
index 94aa285d..fdf6ee21 100644
--- a/atdgen/src/ocaml.ml
+++ b/atdgen/src/ocaml.ml
@@ -169,6 +169,12 @@ let annot_schema_ocaml : Atd.Annot.schema_section =
       Field, "mutable";
       Field, "name";
       Field, "repr";
+      Module_head, "tag";
+      Type_def, "tag";
+      Type_expr, "tag";
+      Variant, "tag";
+      Cell, "tag";
+      Field, "tag";
     ]
   }
 
diff --git a/atdgen/src/oj_emit.ml b/atdgen/src/oj_emit.ml
index e182afb9..60fd9ebb 100644
--- a/atdgen/src/oj_emit.ml
+++ b/atdgen/src/oj_emit.ml
@@ -1338,6 +1338,7 @@ let make_ocaml_files
     ~preprocess_input
     ~ocaml_version
     ~pp_convs
+    ~tags
     atd_file out =
   let ((head, m0), _) =
     match atd_file with
@@ -1345,13 +1346,13 @@ let make_ocaml_files
         Atd.Util.load_file
           ~annot_schema
           ~expand:false ~inherit_fields:true ~inherit_variants:true
-          ?pos_fname ?pos_lnum
+          ?pos_fname ?pos_lnum ~tags
           file
     | None ->
         Atd.Util.read_channel
           ~annot_schema
           ~expand:false ~inherit_fields:true ~inherit_variants:true
-          ?pos_fname ?pos_lnum
+          ?pos_fname ?pos_lnum ~tags
           stdin
   in
 
diff --git a/atdgen/src/oj_emit.mli b/atdgen/src/oj_emit.mli
index 29384958..e21ee25d 100644
--- a/atdgen/src/oj_emit.mli
+++ b/atdgen/src/oj_emit.mli
@@ -15,6 +15,7 @@ val make_ocaml_files
   -> preprocess_input:string option
   -> ocaml_version:(int * int) option
   -> pp_convs:Ocaml.pp_convs
+  -> tags:string list
   -> string option
   -> Ox_emit.target
   -> unit
diff --git a/atdgen/src/omelange_emit.ml b/atdgen/src/omelange_emit.ml
index f9a29b8e..bbe6a0e5 100644
--- a/atdgen/src/omelange_emit.ml
+++ b/atdgen/src/omelange_emit.ml
@@ -713,6 +713,7 @@ let make_ocaml_files
     ~force_defaults:_
     ~ocaml_version
     ~pp_convs:_
+    ~tags
     atd_file out =
   let ((head, m0), _) =
     match atd_file with
@@ -720,13 +721,13 @@ let make_ocaml_files
         Atd.Util.load_file
           ~annot_schema
           ~expand:false ~inherit_fields:true ~inherit_variants:true
-          ?pos_fname ?pos_lnum
+          ?pos_fname ?pos_lnum ~tags
           file
     | None ->
         Atd.Util.read_channel
           ~annot_schema
           ~expand:false ~inherit_fields:true ~inherit_variants:true
-          ?pos_fname ?pos_lnum
+          ?pos_fname ?pos_lnum  ~tags
           stdin
   in
 
diff --git a/atdgen/src/omelange_emit.mli b/atdgen/src/omelange_emit.mli
index a234305d..f225dccf 100644
--- a/atdgen/src/omelange_emit.mli
+++ b/atdgen/src/omelange_emit.mli
@@ -11,6 +11,7 @@ val make_ocaml_files
   -> force_defaults:'a
   -> ocaml_version:'b
   -> pp_convs:'c
+  -> tags:string list
   -> string option
   -> Ox_emit.target
   -> unit
diff --git a/atdgen/src/ov_emit.ml b/atdgen/src/ov_emit.ml
index 68374e74..6731705b 100644
--- a/atdgen/src/ov_emit.ml
+++ b/atdgen/src/ov_emit.ml
@@ -423,6 +423,7 @@ let make_ocaml_files
     ~force_defaults:_
     ~ocaml_version:_
     ~pp_convs
+    ~tags
     atd_file out =
   let ((head, m0), _) =
     match atd_file with
@@ -430,13 +431,13 @@ let make_ocaml_files
         Atd.Util.load_file
           ~annot_schema
           ~expand:false ~inherit_fields:true ~inherit_variants:true
-          ?pos_fname ?pos_lnum
+          ?pos_fname ?pos_lnum ~tags
           file
     | None ->
         Atd.Util.read_channel
           ~annot_schema
           ~expand:false ~inherit_fields:true ~inherit_variants:true
-          ?pos_fname ?pos_lnum
+          ?pos_fname ?pos_lnum ~tags
           stdin
   in
   let tsort =
diff --git a/atdgen/src/ov_emit.mli b/atdgen/src/ov_emit.mli
index afc0295d..b438ec41 100644
--- a/atdgen/src/ov_emit.mli
+++ b/atdgen/src/ov_emit.mli
@@ -12,4 +12,5 @@ val make_ocaml_files
   -> force_defaults:_ (* TODO unused *)
   -> ocaml_version:_ (* TODO unused *)
   -> pp_convs:Ocaml.pp_convs
+  -> tags:string list
   -> string option -> Ox_emit.target -> unit
diff --git a/atdgen/test/dune b/atdgen/test/dune
index 87417b0c..cccb6901 100644
--- a/atdgen/test/dune
+++ b/atdgen/test/dune
@@ -258,6 +258,21 @@
  (package atdgen)
  (action (diff test_annot_error.expected.stdout test_annot_error.stdout)))
  
+(rule
+ (targets test_annot_tags_j.ml test_annot_tags_j.mli)
+ (deps    test_annot_tags.atd)
+ (action  (run %{bin:atdgen} -tag=melange -j -j-std %{deps})))
+
+(rule
+ (alias runtest)
+ (package atdgen)
+ (action (diff test_annot_tags_j.expected.ml test_annot_tags_j.ml)))
+
+(rule
+ (alias runtest)
+ (package atdgen)
+ (action (diff test_annot_tags_j.expected.mli test_annot_tags_j.mli)))
+ 
  ;; inline records are not allowed within poly variant, but allowed in classic
 
 (rule
diff --git a/atdgen/test/test_annot_tags.atd b/atdgen/test/test_annot_tags.atd
new file mode 100644
index 00000000..39ffc66f
--- /dev/null
+++ b/atdgen/test/test_annot_tags.atd
@@ -0,0 +1,6 @@
+type t = {
+  id : int;
+  always_array : string list <ocaml repr="array">;
+  melange_array : string list <ocaml repr="array" tag="melange" tag="ml">;
+  ml_array : string list <ocaml repr="array" tag="ml">;
+}
\ No newline at end of file
diff --git a/atdgen/test/test_annot_tags_j.expected.ml b/atdgen/test/test_annot_tags_j.expected.ml
new file mode 100644
index 00000000..ae1ad422
--- /dev/null
+++ b/atdgen/test/test_annot_tags_j.expected.ml
@@ -0,0 +1,297 @@
+(* Auto-generated from "test_annot_tags.atd" *)
+[@@@ocaml.warning "-27-32-33-35-39"]
+
+type t = Test_annot_tags_t.t = {
+  id: int;
+  always_array: string Atdgen_runtime.Util.ocaml_array;
+  melange_array: string Atdgen_runtime.Util.ocaml_array;
+  ml_array: string list
+}
+
+let write__x_f5dfc61 = (
+  Atdgen_runtime.Oj_run.write_array (
+    Yojson.Safe.write_string
+  )
+)
+let string_of__x_f5dfc61 ?(len = 1024) x =
+  let ob = Buffer.create len in
+  write__x_f5dfc61 ob x;
+  Buffer.contents ob
+let read__x_f5dfc61 = (
+  Atdgen_runtime.Oj_run.read_array (
+    Atdgen_runtime.Oj_run.read_string
+  )
+)
+let _x_f5dfc61_of_string s =
+  read__x_f5dfc61 (Yojson.Safe.init_lexer ()) (Lexing.from_string s)
+let write__x_20d39e2 = (
+  Atdgen_runtime.Oj_run.write_array (
+    Yojson.Safe.write_string
+  )
+)
+let string_of__x_20d39e2 ?(len = 1024) x =
+  let ob = Buffer.create len in
+  write__x_20d39e2 ob x;
+  Buffer.contents ob
+let read__x_20d39e2 = (
+  Atdgen_runtime.Oj_run.read_array (
+    Atdgen_runtime.Oj_run.read_string
+  )
+)
+let _x_20d39e2_of_string s =
+  read__x_20d39e2 (Yojson.Safe.init_lexer ()) (Lexing.from_string s)
+let write__string_list = (
+  Atdgen_runtime.Oj_run.write_list (
+    Yojson.Safe.write_string
+  )
+)
+let string_of__string_list ?(len = 1024) x =
+  let ob = Buffer.create len in
+  write__string_list ob x;
+  Buffer.contents ob
+let read__string_list = (
+  Atdgen_runtime.Oj_run.read_list (
+    Atdgen_runtime.Oj_run.read_string
+  )
+)
+let _string_list_of_string s =
+  read__string_list (Yojson.Safe.init_lexer ()) (Lexing.from_string s)
+let write_t : _ -> t -> _ = (
+  fun ob (x : t) ->
+    Buffer.add_char ob '{';
+    let is_first = ref true in
+    if !is_first then
+      is_first := false
+    else
+      Buffer.add_char ob ',';
+      Buffer.add_string ob "\"id\":";
+    (
+      Yojson.Safe.write_int
+    )
+      ob x.id;
+    if !is_first then
+      is_first := false
+    else
+      Buffer.add_char ob ',';
+      Buffer.add_string ob "\"always_array\":";
+    (
+      write__x_20d39e2
+    )
+      ob x.always_array;
+    if !is_first then
+      is_first := false
+    else
+      Buffer.add_char ob ',';
+      Buffer.add_string ob "\"melange_array\":";
+    (
+      write__x_f5dfc61
+    )
+      ob x.melange_array;
+    if !is_first then
+      is_first := false
+    else
+      Buffer.add_char ob ',';
+      Buffer.add_string ob "\"ml_array\":";
+    (
+      write__string_list
+    )
+      ob x.ml_array;
+    Buffer.add_char ob '}';
+)
+let string_of_t ?(len = 1024) x =
+  let ob = Buffer.create len in
+  write_t ob x;
+  Buffer.contents ob
+let read_t = (
+  fun p lb ->
+    Yojson.Safe.read_space p lb;
+    Yojson.Safe.read_lcurl p lb;
+    let field_id = ref (None) in
+    let field_always_array = ref (None) in
+    let field_melange_array = ref (None) in
+    let field_ml_array = ref (None) in
+    try
+      Yojson.Safe.read_space p lb;
+      Yojson.Safe.read_object_end lb;
+      Yojson.Safe.read_space p lb;
+      let f =
+        fun s pos len ->
+          if pos < 0 || len < 0 || pos + len > String.length s then
+            invalid_arg (Printf.sprintf "out-of-bounds substring position or length: string = %S, requested position = %i, requested length = %i" s pos len);
+          match len with
+            | 2 -> (
+                if String.unsafe_get s pos = 'i' && String.unsafe_get s (pos+1) = 'd' then (
+                  0
+                )
+                else (
+                  -1
+                )
+              )
+            | 8 -> (
+                if String.unsafe_get s pos = 'm' && String.unsafe_get s (pos+1) = 'l' && String.unsafe_get s (pos+2) = '_' && String.unsafe_get s (pos+3) = 'a' && String.unsafe_get s (pos+4) = 'r' && String.unsafe_get s (pos+5) = 'r' && String.unsafe_get s (pos+6) = 'a' && String.unsafe_get s (pos+7) = 'y' then (
+                  3
+                )
+                else (
+                  -1
+                )
+              )
+            | 12 -> (
+                if String.unsafe_get s pos = 'a' && String.unsafe_get s (pos+1) = 'l' && String.unsafe_get s (pos+2) = 'w' && String.unsafe_get s (pos+3) = 'a' && String.unsafe_get s (pos+4) = 'y' && String.unsafe_get s (pos+5) = 's' && String.unsafe_get s (pos+6) = '_' && String.unsafe_get s (pos+7) = 'a' && String.unsafe_get s (pos+8) = 'r' && String.unsafe_get s (pos+9) = 'r' && String.unsafe_get s (pos+10) = 'a' && String.unsafe_get s (pos+11) = 'y' then (
+                  1
+                )
+                else (
+                  -1
+                )
+              )
+            | 13 -> (
+                if String.unsafe_get s pos = 'm' && String.unsafe_get s (pos+1) = 'e' && String.unsafe_get s (pos+2) = 'l' && String.unsafe_get s (pos+3) = 'a' && String.unsafe_get s (pos+4) = 'n' && String.unsafe_get s (pos+5) = 'g' && String.unsafe_get s (pos+6) = 'e' && String.unsafe_get s (pos+7) = '_' && String.unsafe_get s (pos+8) = 'a' && String.unsafe_get s (pos+9) = 'r' && String.unsafe_get s (pos+10) = 'r' && String.unsafe_get s (pos+11) = 'a' && String.unsafe_get s (pos+12) = 'y' then (
+                  2
+                )
+                else (
+                  -1
+                )
+              )
+            | _ -> (
+                -1
+              )
+      in
+      let i = Yojson.Safe.map_ident p f lb in
+      Atdgen_runtime.Oj_run.read_until_field_value p lb;
+      (
+        match i with
+          | 0 ->
+            field_id := (
+              Some (
+                (
+                  Atdgen_runtime.Oj_run.read_int
+                ) p lb
+              )
+            );
+          | 1 ->
+            field_always_array := (
+              Some (
+                (
+                  read__x_20d39e2
+                ) p lb
+              )
+            );
+          | 2 ->
+            field_melange_array := (
+              Some (
+                (
+                  read__x_f5dfc61
+                ) p lb
+              )
+            );
+          | 3 ->
+            field_ml_array := (
+              Some (
+                (
+                  read__string_list
+                ) p lb
+              )
+            );
+          | _ -> (
+              Yojson.Safe.skip_json p lb
+            )
+      );
+      while true do
+        Yojson.Safe.read_space p lb;
+        Yojson.Safe.read_object_sep p lb;
+        Yojson.Safe.read_space p lb;
+        let f =
+          fun s pos len ->
+            if pos < 0 || len < 0 || pos + len > String.length s then
+              invalid_arg (Printf.sprintf "out-of-bounds substring position or length: string = %S, requested position = %i, requested length = %i" s pos len);
+            match len with
+              | 2 -> (
+                  if String.unsafe_get s pos = 'i' && String.unsafe_get s (pos+1) = 'd' then (
+                    0
+                  )
+                  else (
+                    -1
+                  )
+                )
+              | 8 -> (
+                  if String.unsafe_get s pos = 'm' && String.unsafe_get s (pos+1) = 'l' && String.unsafe_get s (pos+2) = '_' && String.unsafe_get s (pos+3) = 'a' && String.unsafe_get s (pos+4) = 'r' && String.unsafe_get s (pos+5) = 'r' && String.unsafe_get s (pos+6) = 'a' && String.unsafe_get s (pos+7) = 'y' then (
+                    3
+                  )
+                  else (
+                    -1
+                  )
+                )
+              | 12 -> (
+                  if String.unsafe_get s pos = 'a' && String.unsafe_get s (pos+1) = 'l' && String.unsafe_get s (pos+2) = 'w' && String.unsafe_get s (pos+3) = 'a' && String.unsafe_get s (pos+4) = 'y' && String.unsafe_get s (pos+5) = 's' && String.unsafe_get s (pos+6) = '_' && String.unsafe_get s (pos+7) = 'a' && String.unsafe_get s (pos+8) = 'r' && String.unsafe_get s (pos+9) = 'r' && String.unsafe_get s (pos+10) = 'a' && String.unsafe_get s (pos+11) = 'y' then (
+                    1
+                  )
+                  else (
+                    -1
+                  )
+                )
+              | 13 -> (
+                  if String.unsafe_get s pos = 'm' && String.unsafe_get s (pos+1) = 'e' && String.unsafe_get s (pos+2) = 'l' && String.unsafe_get s (pos+3) = 'a' && String.unsafe_get s (pos+4) = 'n' && String.unsafe_get s (pos+5) = 'g' && String.unsafe_get s (pos+6) = 'e' && String.unsafe_get s (pos+7) = '_' && String.unsafe_get s (pos+8) = 'a' && String.unsafe_get s (pos+9) = 'r' && String.unsafe_get s (pos+10) = 'r' && String.unsafe_get s (pos+11) = 'a' && String.unsafe_get s (pos+12) = 'y' then (
+                    2
+                  )
+                  else (
+                    -1
+                  )
+                )
+              | _ -> (
+                  -1
+                )
+        in
+        let i = Yojson.Safe.map_ident p f lb in
+        Atdgen_runtime.Oj_run.read_until_field_value p lb;
+        (
+          match i with
+            | 0 ->
+              field_id := (
+                Some (
+                  (
+                    Atdgen_runtime.Oj_run.read_int
+                  ) p lb
+                )
+              );
+            | 1 ->
+              field_always_array := (
+                Some (
+                  (
+                    read__x_20d39e2
+                  ) p lb
+                )
+              );
+            | 2 ->
+              field_melange_array := (
+                Some (
+                  (
+                    read__x_f5dfc61
+                  ) p lb
+                )
+              );
+            | 3 ->
+              field_ml_array := (
+                Some (
+                  (
+                    read__string_list
+                  ) p lb
+                )
+              );
+            | _ -> (
+                Yojson.Safe.skip_json p lb
+              )
+        );
+      done;
+      assert false;
+    with Yojson.End_of_object -> (
+        (
+          {
+            id = (match !field_id with Some x -> x | None -> Atdgen_runtime.Oj_run.missing_field p "id");
+            always_array = (match !field_always_array with Some x -> x | None -> Atdgen_runtime.Oj_run.missing_field p "always_array");
+            melange_array = (match !field_melange_array with Some x -> x | None -> Atdgen_runtime.Oj_run.missing_field p "melange_array");
+            ml_array = (match !field_ml_array with Some x -> x | None -> Atdgen_runtime.Oj_run.missing_field p "ml_array");
+          }
+         : t)
+      )
+)
+let t_of_string s =
+  read_t (Yojson.Safe.init_lexer ()) (Lexing.from_string s)
diff --git a/atdgen/test/test_annot_tags_j.expected.mli b/atdgen/test/test_annot_tags_j.expected.mli
new file mode 100644
index 00000000..6383e822
--- /dev/null
+++ b/atdgen/test/test_annot_tags_j.expected.mli
@@ -0,0 +1,30 @@
+(* Auto-generated from "test_annot_tags.atd" *)
+[@@@ocaml.warning "-27-32-33-35-39"]
+
+type t = Test_annot_tags_t.t = {
+  id: int;
+  always_array: string Atdgen_runtime.Util.ocaml_array;
+  melange_array: string Atdgen_runtime.Util.ocaml_array;
+  ml_array: string list
+}
+
+val write_t :
+  Buffer.t -> t -> unit
+  (** Output a JSON value of type {!type:t}. *)
+
+val string_of_t :
+  ?len:int -> t -> string
+  (** Serialize a value of type {!type:t}
+      into a JSON string.
+      @param len specifies the initial length
+                 of the buffer used internally.
+                 Default: 1024. *)
+
+val read_t :
+  Yojson.Safe.lexer_state -> Lexing.lexbuf -> t
+  (** Input JSON data of type {!type:t}. *)
+
+val t_of_string :
+  string -> t
+  (** Deserialize JSON data of type {!type:t}. *)
+
diff --git a/atdj/src/atdj_env.ml b/atdj/src/atdj_env.ml
index 4f72c78b..14fadd54 100644
--- a/atdj/src/atdj_env.ml
+++ b/atdj/src/atdj_env.ml
@@ -13,6 +13,7 @@ type ty =
 
 type env_t = {
   module_items : (string * Atd.Ast.type_expr) list;
+  tags         : string list;
   package      : string;
   package_dir  : string;
   input_file   : string option;
@@ -20,6 +21,7 @@ type env_t = {
 
 let default_env = {
   module_items = [];
+  tags         = [];
   package      = "out";
   package_dir  = "out";
   input_file   = None;
diff --git a/atdj/src/atdj_main.ml b/atdj/src/atdj_main.ml
index 3b5a4923..81507391 100644
--- a/atdj/src/atdj_main.ml
+++ b/atdj/src/atdj_main.ml
@@ -6,7 +6,14 @@ open Atdj_env
 let args_spec env = Arg.align
     [ "-package",
       Arg.String (fun x -> env := { !env with package = x }),
-      " Package name of generated files"
+      " Package name of generated files";
+
+      "-tag",
+      Arg.String (fun x -> env := { !env with tags = (x :: !env.tags) }),
+      " Only evaluate annotations which have either \n
+          - the provided TAG as a field value <... tag=TAG>, \n
+          - or have no tags specified. \n
+        Option can be used multiple times to specify several tags"
     ]
 
 let usage_msg = "Usage: " ^ Sys.argv.(0) ^ " <options> <file>\nOptions are:"
@@ -64,7 +71,7 @@ let main () =
   (* Parse ATD file *)
   let (atd_head, atd_module), _original_types =
     Atd.Util.load_file
-      ~expand:false ~inherit_fields:true ~inherit_variants:true input_file
+      ~expand:false ~inherit_fields:true ~inherit_variants:true ~tags:env.tags input_file
   in
   let env = {
     env with
diff --git a/atdj/src/dune b/atdj/src/dune
index 78e671c9..07d944ea 100644
--- a/atdj/src/dune
+++ b/atdj/src/dune
@@ -2,4 +2,4 @@
  (name atdj_main)
  (public_name atdj)
  (package atdj)
- (libraries re atd))
+ (libraries unix re atd))
diff --git a/atdpy/src/bin/Atdpy_main.ml b/atdpy/src/bin/Atdpy_main.ml
index bfcf7317..ad917e80 100644
--- a/atdpy/src/bin/Atdpy_main.ml
+++ b/atdpy/src/bin/Atdpy_main.ml
@@ -7,6 +7,7 @@ open Cmdliner
 
 type conf = {
   input_files: string list;
+  tags: string list;
   version: bool;
 }
 
@@ -18,7 +19,7 @@ let run conf =
   else
     conf.input_files
     |> List.iter (fun atd_file ->
-      Atdpy.Codegen.run_file atd_file
+      Atdpy.Codegen.run_file ~tags:conf.tags atd_file
     )
 
 (***************************************************************************)
@@ -38,6 +39,13 @@ let input_files_term =
   let default = [] in
   Arg.value (Arg.pos_all Arg.file default info)
 
+let tags_term =
+  let info =
+    Arg.info ["tag"]
+      ~doc:"Only evaluate annotations which have either the provided TAG as a field value <... tag=TAG>, or have no tags specified.\nOption can be used multiple times to specify several tags"
+  in
+  Arg.value (Arg.opt_all Arg.string [] info)
+  
 let version_term =
   let info =
     Arg.info ["version"]
@@ -94,14 +102,16 @@ type bar = [
 ]
 
 let cmdline_term run =
-  let combine input_files version =
+  let combine input_files tags version =
     run {
       input_files;
+      tags;
       version;
     }
   in
   Term.(const combine
         $ input_files_term
+        $ tags_term
         $ version_term
        )
 
diff --git a/atdpy/src/lib/Codegen.ml b/atdpy/src/lib/Codegen.ml
index 2e3e7eec..7fc86097 100644
--- a/atdpy/src/lib/Codegen.ml
+++ b/atdpy/src/lib/Codegen.ml
@@ -46,6 +46,12 @@ let annot_schema_python : Atd.Annot.schema_section =
       Type_def, "decorator";
       Type_expr, "repr";
       Field, "default";
+      Module_head, "tag";
+      Type_def, "tag";
+      Type_expr, "tag";
+      Variant, "tag";
+      Cell, "tag";
+      Field, "tag";
     ]
   }
 
@@ -1230,7 +1236,7 @@ let to_file ~atd_filename ~head (items : A.module_body) dst_path =
   |> double_spaced
   |> Indent.to_file ~indent:4 dst_path
 
-let run_file src_path =
+let run_file ~tags src_path =
   let src_name = Filename.basename src_path in
   let dst_name =
     (if Filename.check_suffix src_name ".atd" then
@@ -1247,6 +1253,7 @@ let run_file src_path =
       ~keep_builtins:true
       ~inherit_fields:true
       ~inherit_variants:true
+      ~tags
       src_path
   in
   let full_module = Atd.Ast.use_only_specific_variants full_module in
diff --git a/atdpy/src/lib/Codegen.mli b/atdpy/src/lib/Codegen.mli
index 941192d1..f6cef54d 100644
--- a/atdpy/src/lib/Codegen.mli
+++ b/atdpy/src/lib/Codegen.mli
@@ -4,4 +4,4 @@
 
 (** Take ATD type definitions and translate them to Python, writing
     them out to a file which should have the '.py' extension. *)
-val run_file : string -> unit
+val run_file : tags:string list -> string -> unit
diff --git a/atds/src/atds_env.ml b/atds/src/atds_env.ml
index 1d7fdb3c..7226b9fb 100644
--- a/atds/src/atds_env.ml
+++ b/atds/src/atds_env.ml
@@ -5,6 +5,7 @@ type ty_name = string
 
 type env_t = {
   module_items : (string * Atd.Ast.type_expr) list;
+  tags         : string list;
   package      : string;
   input_file   : string option;
   output       : out_channel;
@@ -12,6 +13,7 @@ type env_t = {
 
 let default_env = {
   module_items = [];
+  tags         = [];
   package      = "out";
   input_file   = None;
   output       = stdout;
diff --git a/atds/src/atds_main.ml b/atds/src/atds_main.ml
index 3fdfc867..5eab1cc5 100644
--- a/atds/src/atds_main.ml
+++ b/atds/src/atds_main.ml
@@ -9,7 +9,13 @@ let args_spec env = Arg.align
       " Package name of generated files";
       "-o",
       Arg.String (fun x -> env := { !env with output = open_out x }),
-      " File name for Scala output"
+      " File name for Scala output";
+      "-tag",
+      Arg.String (fun x -> env := { !env with tags = (x :: !env.tags) }),
+      " Only evaluate annotations which have either \n
+          - the provided TAG as a field value <... tag=TAG>, \n
+          - or have no tags specified. \n
+        Option can be used multiple times to specify several tags"
     ]
 
 let usage_msg = "Usage: " ^ Sys.argv.(0) ^ " <options> <file>\nOptions are:"
@@ -49,7 +55,7 @@ let main () =
   (* Parse ATD file *)
   let (atd_head, atd_module), _original_types =
     Atd.Util.load_file
-      ~expand:false ~inherit_fields:true ~inherit_variants:true input_file
+      ~expand:false ~inherit_fields:true ~inherit_variants:true ~tags:env.tags input_file
   in
   let env = {
     env with
diff --git a/atdts/src/bin/Atdts_main.ml b/atdts/src/bin/Atdts_main.ml
index dd38d126..865a063b 100644
--- a/atdts/src/bin/Atdts_main.ml
+++ b/atdts/src/bin/Atdts_main.ml
@@ -7,6 +7,7 @@ open Cmdliner
 
 type conf = {
   input_files: string list;
+  tags: string list;
   version: bool;
 }
 
@@ -18,7 +19,7 @@ let run conf =
   else
     conf.input_files
     |> List.iter (fun atd_file ->
-      Atdts.Codegen.run_file atd_file
+      Atdts.Codegen.run_file ~tags:conf.tags atd_file
     )
 
 (***************************************************************************)
@@ -38,6 +39,13 @@ let input_files_term =
   let default = [] in
   Arg.value (Arg.pos_all Arg.file default info)
 
+let tags_term =
+  let info =
+    Arg.info ["tag"]
+      ~doc:"Only evaluate annotations which have either the provided TAG as a field value <... tag=TAG>, or have no tags specified.\nOption can be used multiple times to specify several tags"
+  in
+  Arg.value (Arg.opt_all Arg.string [] info)  
+
 let version_term =
   let info =
     Arg.info ["version"]
@@ -92,14 +100,16 @@ type bar = [
 ]
 
 let cmdline_term run =
-  let combine input_files version =
+  let combine input_files tags version =
     run {
       input_files;
+      tags;
       version;
     }
   in
   Term.(const combine
         $ input_files_term
+        $ tags_term
         $ version_term
        )
 
diff --git a/atdts/src/lib/Codegen.ml b/atdts/src/lib/Codegen.ml
index 5473f4f0..850c6abd 100644
--- a/atdts/src/lib/Codegen.ml
+++ b/atdts/src/lib/Codegen.ml
@@ -25,6 +25,12 @@ let annot_schema_ts : Atd.Annot.schema_section =
     fields = [
       Type_expr, "repr";
       Field, "default";
+      Module_head, "tag";
+      Type_def, "tag";
+      Type_expr, "tag";
+      Variant, "tag";
+      Cell, "tag";
+      Field, "tag";
     ]
   }
 
@@ -1161,7 +1167,7 @@ let to_file ~atd_filename (items : A.module_body) dst_path =
   |> spaced
   |> Indent.to_file ~indent:2 dst_path
 
-let run_file src_path =
+let run_file ~tags src_path =
   let src_name = Filename.basename src_path in
   let dst_name =
     (if Filename.check_suffix src_name ".atd" then
@@ -1178,6 +1184,7 @@ let run_file src_path =
       ~keep_builtins:true
       ~inherit_fields:true
       ~inherit_variants:true
+      ~tags
       src_path
   in
   let full_module =
diff --git a/atdts/src/lib/Codegen.mli b/atdts/src/lib/Codegen.mli
index e72afe06..f3a71574 100644
--- a/atdts/src/lib/Codegen.mli
+++ b/atdts/src/lib/Codegen.mli
@@ -4,4 +4,4 @@
 
 (** Take ATD type definitions and translate them to TypeScript, writing
     them out to a file which should have the '.ts' extension. *)
-val run_file : string -> unit
+val run_file : tags:string list -> string -> unit