diff --git a/CMakeLists.txt b/CMakeLists.txt
index c57af72..d6a8e83 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -85,6 +85,11 @@ endif()
 #  test_big_endian(WORDS_BIGENDIAN)
 #endif()
 
+if (EMSCRIPTEN)
+    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -DEMSCRIPTEN")
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DEMSCRIPTEN")
+    set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} --memory-init-file 0")
+endif()
 
 #set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
 set(CMAKE_CXX_STANDARD 11)
diff --git a/README.md b/README.md
index 248cd29..d9f7c30 100644
--- a/README.md
+++ b/README.md
@@ -170,5 +170,11 @@ scripts\speck\build_win.bat
 
 dll library is outputted to `libs/windows` directory.
 
+## emscripten
+
+```
+./scripts/speck/build_emscripten.sh
+```
+
 # License
 [![FOSSA Status](https://app.fossa.io/api/projects/git%2Bhttps%3A%2F%2Fgithub.com%2FNaruto%2Fsimon-speck-c.svg?type=large)](https://app.fossa.io/projects/git%2Bhttps%3A%2F%2Fgithub.com%2FNaruto%2Fsimon-speck-c?ref=badge_large)
diff --git a/include/speck/speck.h b/include/speck/speck.h
index b28b1d6..f4b0e94 100644
--- a/include/speck/speck.h
+++ b/include/speck/speck.h
@@ -24,6 +24,9 @@
 #define SPECK_H
 
 #include <stdint.h>
+#if EMSCRIPTEN
+#include <emscripten/emscripten.h>
+#endif
 
 #ifdef SPECKAPI
 #undef SPECKAPI
@@ -31,6 +34,8 @@
 
 #if _WIN32
 #define SPECKAPI __declspec(dllexport)
+#elif EMSCRIPTEN
+#define SPECKAPI EMSCRIPTEN_KEEPALIVE
 #else
 #ifdef __GNUC__
 #if __GNUC__ >= 4
diff --git a/scripts/speck/build_emscripten.sh b/scripts/speck/build_emscripten.sh
new file mode 100755
index 0000000..e7e2070
--- /dev/null
+++ b/scripts/speck/build_emscripten.sh
@@ -0,0 +1,29 @@
+#!/bin/bash -xe
+
+SCRIPTDIR=`dirname $0`
+SCRIPTDIR=`cd $SCRIPTDIR && pwd -P`
+BASEDIR=${SCRIPTDIR}/../..
+BASEDIR=`cd ${BASEDIR} && pwd -P`
+
+pushd ${BASEDIR} > /dev/null
+/bin/rm -rf build
+/bin/mkdir build
+# build
+pushd build > /dev/null
+emcmake cmake -DENABLE_STATIC=ON -DCMAKE_BUILD_TYPE=Release ..
+cmake --build .
+
+# rename .c.o to .bc
+ar x libspeck.a
+for f in *.c.o; do
+    mv $f ${f%.c.o}.bc
+done
+zip libspeck.zip *.bc
+
+popd > /dev/null
+
+/bin/rm -rf libs/emscripten
+/bin/mkdir -p libs/emscripten
+/bin/cp ./build/libspeck.zip libs/emscripten
+
+popd > /dev/null