diff --git a/src/files/files.cpp b/src/files/files.cpp
index 8f459dcc..55ca345f 100644
--- a/src/files/files.cpp
+++ b/src/files/files.cpp
@@ -6,6 +6,7 @@
 #include <stdint.h>
 #include <stdexcept>
 #include "../coders/json.h"
+#include "../coders/gzip.h"
 #include "../util/stringutil.h"
 #include "../data/dynamic.h"
 
@@ -32,21 +33,21 @@ void files::rafile::read(char* buffer, std::streamsize size) {
     file.read(buffer, size);
 }
 
-bool files::write_bytes(fs::path filename, const char* data, size_t size) {
+bool files::write_bytes(fs::path filename, const ubyte* data, size_t size) {
 	std::ofstream output(filename, std::ios::binary);
 	if (!output.is_open())
 		return false;
-	output.write(data, size);
+	output.write((const char*)data, size);
 	output.close();
 	return true;
 }
 
-uint files::append_bytes(fs::path filename, const char* data, size_t size) {
+uint files::append_bytes(fs::path filename, const ubyte* data, size_t size) {
 	std::ofstream output(filename, std::ios::binary | std::ios::app);
 	if (!output.is_open())
 		return 0;
 	uint position = output.tellp();
-	output.write(data, size);
+	output.write((const char*)data, size);
 	output.close();
 	return position;
 }
@@ -60,7 +61,7 @@ bool files::read(fs::path filename, char* data, size_t size) {
 	return true;
 }
 
-char* files::read_bytes(fs::path filename, size_t& length) {
+ubyte* files::read_bytes(fs::path filename, size_t& length) {
 	std::ifstream input(filename, std::ios::binary);
 	if (!input.is_open())
 		return nullptr;
@@ -71,17 +72,17 @@ char* files::read_bytes(fs::path filename, size_t& length) {
 	std::unique_ptr<char> data(new char[length]);
 	input.read(data.get(), length);
 	input.close();
-	return data.release();
+	return (ubyte*)data.release();
 }
 
 std::string files::read_string(fs::path filename) {
 	size_t size;
-	std::unique_ptr<char> chars (read_bytes(filename, size));
-	if (chars == nullptr) {
+	std::unique_ptr<ubyte[]> bytes (read_bytes(filename, size));
+	if (bytes == nullptr) {
 		throw std::runtime_error("could not to load file '"+
 								 filename.string()+"'");
 	}
-	return std::string(chars.get(), size);
+	return std::string((const char*)bytes.get(), size);
 }
 
 bool files::write_string(fs::path filename, const std::string content) {
@@ -94,27 +95,21 @@ bool files::write_string(fs::path filename, const std::string content) {
 }
 
 bool files::write_json(fs::path filename, const dynamic::Map* obj, bool nice) {
-    // -- binary json tests
-    //return write_binary_json(fs::path(filename.u8string()+".bin"), obj);
     return files::write_string(filename, json::stringify(obj, nice, "  "));
 }
 
-bool files::write_binary_json(fs::path filename, const dynamic::Map* obj) {
-    std::vector<ubyte> bytes = json::to_binary(obj);
-    return files::write_bytes(filename, (const char*)bytes.data(), bytes.size());
+bool files::write_binary_json(fs::path filename, const dynamic::Map* obj, bool compression) {
+    auto bytes = json::to_binary(obj);
+    if (compression) {
+        bytes = gzip::compress(bytes.data(), bytes.size());
+    }
+    return files::write_bytes(filename, bytes.data(), bytes.size());
 }
 
 std::unique_ptr<dynamic::Map> files::read_json(fs::path filename) {
-    // binary json tests
-    // fs::path binfile = fs::path(filename.u8string()+".bin");
-    // if (fs::is_regular_file(binfile)){
-    //     return read_binary_json(binfile);
-    // }
-
 	std::string text = files::read_string(filename);
 	try {
 		auto obj = json::parse(filename.string(), text);
-        //write_binary_json(binfile, obj);
         return obj;
 	} catch (const parsing_error& error) {
         std::cerr << error.errorLog() << std::endl;
@@ -124,8 +119,10 @@ std::unique_ptr<dynamic::Map> files::read_json(fs::path filename) {
 
 std::unique_ptr<dynamic::Map> files::read_binary_json(fs::path file) {
     size_t size;
-    std::unique_ptr<char[]> bytes (files::read_bytes(file, size));
-    return std::unique_ptr<dynamic::Map>(json::from_binary((const ubyte*)bytes.get(), size));
+    std::unique_ptr<ubyte[]> bytes (files::read_bytes(file, size));
+    return std::unique_ptr<dynamic::Map>(
+        json::from_binary(bytes.get(), size)
+    );
 }
 
 std::vector<std::string> files::read_list(fs::path filename) {
diff --git a/src/files/files.h b/src/files/files.h
index 4e136fa6..f7515712 100644
--- a/src/files/files.h
+++ b/src/files/files.h
@@ -27,15 +27,33 @@ namespace files {
         size_t length() const;
     };
 
+    /* Write bytes array to the file without any extra data */
+    extern bool write_bytes(fs::path, const ubyte* data, size_t size);
 
-    extern bool write_bytes(fs::path, const char* data, size_t size);
-    extern uint append_bytes(fs::path, const char* data, size_t size);
+    /* Append bytes array to the file without any extra data */
+    extern uint append_bytes(fs::path, const ubyte* data, size_t size);
+
+    /* Write string to the file */
     extern bool write_string(fs::path filename, const std::string content);
-    extern bool write_json(fs::path filename, const dynamic::Map* obj, bool nice=true);
-    extern bool write_binary_json(fs::path filename, const dynamic::Map* obj);
+
+    /* Write dynamic data to the JSON file
+       @param nice if true, 
+         human readable format will be used, otherwise minimal */
+    extern bool write_json(
+        fs::path filename, 
+        const dynamic::Map* obj, 
+        bool nice=true);
+
+    /* Write dynamic data to the binary JSON file
+       (see src/coders/binary_json_spec.md)
+       @param compressed use gzip compression */
+    extern bool write_binary_json(
+        fs::path filename, 
+        const dynamic::Map* obj, 
+        bool compressed=false);
 
     extern bool read(fs::path, char* data, size_t size);
-    extern char* read_bytes(fs::path, size_t& length);
+    extern ubyte* read_bytes(fs::path, size_t& length);
     extern std::string read_string(fs::path filename);
     extern std::unique_ptr<dynamic::Map> read_json(fs::path file);
     extern std::unique_ptr<dynamic::Map> read_binary_json(fs::path file);