diff --git a/CHANGELOG.md b/CHANGELOG.md
index 95de0280cf..a4debfd5cb 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,7 @@
 
 - Deprecate JSX 3 https://github.com/rescript-lang/rescript-compiler/pull/7042
 - Deprecate js_cast.res https://github.com/rescript-lang/rescript-compiler/pull/7074
+- Deprecate top-level `"suffix"` option in `rescript.json`. https://github.com/rescript-lang/rescript-compiler/pull/7056
 
 # 11.1.4
 
diff --git a/docs/docson/build-schema.json b/docs/docson/build-schema.json
index c0139a7e9f..f8b6328497 100644
--- a/docs/docson/build-schema.json
+++ b/docs/docson/build-schema.json
@@ -5,10 +5,6 @@
       "enum": ["esmodule", "commonjs", "es6", "es6-global"],
       "description": "es6 and es6-global are deprecated. Default: commonjs."
     },
-    "suffix-spec": {
-      "type": "string",
-      "description": "Suffix of generated js files. Default: .js. May contain letters, digits, \"-\", \"_\" and \".\" and must end with .js, .mjs or .cjs."
-    },
     "module-format-object": {
       "type": "object",
       "properties": {
@@ -20,7 +16,8 @@
           "description": "Default: false."
         },
         "suffix": {
-          "$ref": "#/definitions/suffix-spec"
+          "type": "string",
+          "description": "Suffix of generated js files. Default: .js. May contain letters, digits, \"-\", \"_\" and \".\" and must end with .js, .mjs or .cjs."
         }
       },
       "required": ["module"]
@@ -487,9 +484,6 @@
       },
       "description": "(Not needed usually) external include directories, which will be applied `-I` to all compilation units"
     },
-    "suffix": {
-      "$ref": "#/definitions/suffix-spec"
-    },
     "reanalyze": {
       "$ref": "#/definitions/reanalyze",
       "description": "Configure reanalyze, a static code analysis tool for ReScript."
diff --git a/jscomp/bsb/bsb_package_specs.ml b/jscomp/bsb/bsb_package_specs.ml
index bcb88c90ac..8bbecfa2b1 100644
--- a/jscomp/bsb/bsb_package_specs.ml
+++ b/jscomp/bsb/bsb_package_specs.ml
@@ -43,14 +43,17 @@ let bad_module_format_message_exn ~loc format =
      of:  %s or %s"
     format Literals.esmodule Literals.commonjs
 
+let deprecated_option ~loc x message =
+  let loc_end =
+    {loc with Lexing.pos_cnum = loc.Lexing.pos_cnum + String.length x}
+  in
+  let loc = {Warnings.loc_start = loc; loc_end; loc_ghost = false} in
+  Location.deprecated loc message
+
 let supported_format (x : string) loc : Ext_module_system.t =
   let _ =
     if x = Literals.es6 || x = Literals.es6_global then
-      let loc_end =
-        {loc with Lexing.pos_cnum = loc.Lexing.pos_cnum + String.length x}
-      in
-      let loc = {Warnings.loc_start = loc; loc_end; loc_ghost = false} in
-      Location.deprecated loc
+      deprecated_option ~loc x 
         (Printf.sprintf "Option \"%s\" is deprecated. Use \"%s\" instead." x
            Literals.esmodule)
   in
@@ -196,10 +199,14 @@ let list_dirs_by (package_specs : t) (f : string -> unit) =
 type json_map = Ext_json_types.t Map_string.t
 
 let extract_js_suffix_exn (map : json_map) : string =
+  let deprecation = "The \"suffix\" option at the top level is deprecated. Move the \"suffix\" setting into each \"package-specs\" entry." in
   match map.?(Bsb_build_schemas.suffix) with
   | None -> Literals.suffix_js
-  | Some (Str { str = suffix; _ }) when validate_js_suffix suffix -> suffix
-  | Some ((Str {str; _}) as config)  -> 
+  | Some (Str { str = suffix; loc }) when validate_js_suffix suffix ->
+    deprecated_option ~loc Literals.suffix_js deprecation;
+    suffix
+  | Some ((Str {str; loc}) as config)  -> 
+    deprecated_option ~loc Literals.suffix_js deprecation;
     Bsb_exception.config_error config
       ("invalid suffix \"" ^ str ^ "\". The suffix and may contain letters, digits, \"-\", \"_\" and \".\" and must end with .js, .mjs or .cjs.")
   | Some config ->