diff --git a/kernel/register.cc b/kernel/register.cc
index 4dfa79845..4e8e62741 100644
--- a/kernel/register.cc
+++ b/kernel/register.cc
@@ -19,6 +19,7 @@
 
 #include "kernel/yosys.h"
 #include "kernel/satgen.h"
+#include "kernel/json.h"
 
 #include <string.h>
 #include <stdlib.h>
@@ -763,6 +764,7 @@ struct SimHelper {
 	string source;
 	string desc;
 	string code;
+	string group;
 	string ver;
 };
 
@@ -950,6 +952,77 @@ struct HelpPass : public Pass {
 		// close
 		fclose(f);
 	}
+	bool dump_cells_json(PrettyJson &json) {
+		// init json
+		json.begin_object();
+		json.entry("version", "Yosys internal cells");
+		json.entry("generator", yosys_version_str);
+
+		dict<string, dict<string, pair<SimHelper, CellType>>> groups;
+
+		// iterate over cells
+		bool raise_error = false;
+		for (auto &it : yosys_celltypes.cell_types) {
+			auto name = it.first.str();
+			if (cell_help_messages.contains(name)) {
+				auto cell_help = cell_help_messages.get(name);
+				dict<string, pair<SimHelper, CellType>> *cell_group;
+				if (groups.count(cell_help.group) != 0) {
+					cell_group = &groups.at(cell_help.group);
+				} else {
+					cell_group = new dict<string, pair<SimHelper, CellType>>();
+					groups.emplace(cell_help.group, *cell_group);
+				}
+				auto cell_pair = pair<SimHelper, CellType>(cell_help, it.second);
+				cell_group->emplace(name, cell_pair);
+			} else {
+				log("ERROR: Missing cell help for cell '%s'.\n", name.c_str());
+				raise_error |= true;
+			}
+		}
+
+		// write to json
+		json.name("groups");
+		json.begin_array();
+		groups.sort();
+		for (auto &it : groups) {
+			json.begin_object();
+			json.name("group"); json.value(it.first.c_str());
+			json.name("cells"); json.begin_array();
+			for (auto &it2 : it.second) {
+				auto ch = it2.second.first;
+				auto ct = it2.second.second;
+				json.begin_object();
+				json.name("cell"); json.value(ch.name);
+				json.name("title"); json.value(ch.title);
+				json.name("ports"); json.value(ch.ports);
+				json.name("source"); json.value(ch.source);
+				json.name("desc"); json.value(ch.desc);
+				json.name("code"); json.value(ch.code);
+				json.name("inputs"); json.begin_array();
+				for (auto &input : ct.inputs)
+					json.value(input.c_str());
+				json.end_array();
+				json.name("outputs"); json.begin_array();
+				for (auto &output : ct.outputs)
+					json.value(output.c_str());
+				json.end_array();
+				dict<string, bool> prop_dict = {
+					{"is_evaluable", ct.is_evaluable},
+					{"is_combinatorial", ct.is_combinatorial},
+					{"is_synthesizable", ct.is_synthesizable},
+				};
+				json.name("properties"); json.value(prop_dict);
+				json.end_object();
+			}
+			json.end_array();
+			json.end_object();
+		}
+		json.end_array();
+
+		json.end_object();
+		return raise_error;
+	}
 	void execute(std::vector<std::string> args, RTLIL::Design*) override
 	{
 		if (args.size() == 1) {
@@ -1053,6 +1126,16 @@ struct HelpPass : public Pass {
 			else
 				log("No such command or cell type: %s\n", args[1].c_str());
 			return;
+		} else if (args.size() == 3) {
+			if (args[1] == "-dump-cells-json") {
+				PrettyJson json;
+				if (!json.write_to_file(args[2]))
+					log_error("Can't open file `%s' for writing: %s\n", args[2].c_str(), strerror(errno));
+				if (dump_cells_json(json)) {
+					log_error("One or more cells defined in celltypes.h are missing help documentation.\n");
+				}
+			}
+			return;
 		}
 
 		help();
diff --git a/techlibs/common/cellhelp.py b/techlibs/common/cellhelp.py
index 0cfb2052f..299b7affd 100644
--- a/techlibs/common/cellhelp.py
+++ b/techlibs/common/cellhelp.py
@@ -12,6 +12,7 @@ class SimHelper:
     source: str = ""
     desc: list[str]
     code: list[str]
+    group: str = ""
     ver: str = "1"
 
     def __init__(self) -> None:
@@ -19,7 +20,7 @@ class SimHelper:
     
     def __str__(self) -> str:
         printed_fields = [
-            "name", "title", "ports", "source", "desc", "code", "ver",
+            "name", "title", "ports", "source", "desc", "code", "group", "ver",
         ]
         # generate C++ struct
         val = f"cell_help[{json.dumps(self.name)}] = "
@@ -28,6 +29,7 @@ class SimHelper:
             field_val = getattr(self, field)
             if isinstance(field_val, list):
                 field_val = "\n".join(field_val)
+            field_val = field_val.strip()
             val += f'  {json.dumps(field_val)},\n'
         val += "};\n"
         return val
@@ -80,9 +82,23 @@ for line in fileinput.input():
         if simHelper.ver == "1" and short_filename == "simcells.v":
             # default simcells parsing
             simcells_reparse(simHelper)
+
+        # check help
         if not simHelper.desc:
-            # no help
             simHelper.desc.append("No help message for this cell type found.\n")
+        elif simHelper.ver == "1" and short_filename == "simlib.v" and simHelper.desc[1].startswith('    '):
+            simHelper.desc.pop(1)
+
+        # check group
+        if not simHelper.group:
+            if short_filename == 'simcells.v':
+                simHelper.group = "gate_"
+            elif short_filename == 'simlib.v':
+                simHelper.group = "word_"
+            simHelper.group += "other"
+
+        # dump
         print(simHelper)
+        # new
         simHelper = SimHelper()
 
diff --git a/techlibs/common/simlib.v b/techlibs/common/simlib.v
index 6bcace498..b8a754825 100644
--- a/techlibs/common/simlib.v
+++ b/techlibs/common/simlib.v
@@ -33,11 +33,10 @@
 
 // --------------------------------------------------------
 
-//  |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
-//-
-//-     $not (A, Y)
-//-
-//- A bit-wise inverter. This corresponds to the Verilog unary prefix '~' operator.
+//* ver 2
+//* title Bit-wise inverter
+//* group unary
+//- This corresponds to the Verilog unary prefix '~' operator.
 //-
 module \$not (A, Y);
 
@@ -63,6 +62,7 @@ endmodule
 //  |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
 //-
 //-     $pos (A, Y)
+//* group unary
 //-
 //- A buffer. This corresponds to the Verilog unary prefix '+' operator.
 //-
@@ -111,6 +111,7 @@ endmodule
 //  |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
 //-
 //-     $neg (A, Y)
+//* group unary
 //-
 //- An arithmetic inverter. This corresponds to the Verilog unary prefix '-' operator.
 //-
@@ -258,6 +259,7 @@ endmodule
 //  |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
 //-
 //-     $reduce_and (A, Y)
+//* group unary
 //-
 //- An AND reduction. This corresponds to the Verilog unary prefix '&' operator.
 //-
@@ -285,6 +287,7 @@ endmodule
 //  |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
 //-
 //-     $reduce_or (A, Y)
+//* group unary
 //-
 //- An OR reduction. This corresponds to the Verilog unary prefix '|' operator.
 //-
@@ -312,6 +315,7 @@ endmodule
 //  |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
 //-
 //-     $reduce_xor (A, Y)
+//* group unary
 //-
 //- A XOR reduction. This corresponds to the Verilog unary prefix '^' operator.
 //-
@@ -339,6 +343,7 @@ endmodule
 //  |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
 //-
 //-     $reduce_xnor (A, Y)
+//* group unary
 //-
 //- A XNOR reduction. This corresponds to the Verilog unary prefix '~^' operator.
 //-
@@ -366,6 +371,7 @@ endmodule
 //  |---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|---v---|
 //-
 //-     $reduce_bool (A, Y)
+//* group unary
 //-
 //- An OR reduction. This cell type is used instead of $reduce_or when a signal is
 //- implicitly converted to a boolean signal, e.g. for operands of '&&' and '||'.
@@ -1359,6 +1365,7 @@ endmodule
 //-
 //- A logical inverter. This corresponds to the Verilog unary prefix '!' operator.
 //-
+//* group unary
 module \$logic_not (A, Y);
 
 parameter A_SIGNED = 0;