diff --git a/external/CMakeLists.txt b/external/CMakeLists.txt
index 1d9cb16..9792c9e 100644
--- a/external/CMakeLists.txt
+++ b/external/CMakeLists.txt
@@ -1,11 +1,11 @@
 set(CMAKE_EXPORT_NO_PACKAGE_REGISTRY ON)
 
 set(SNAPPY_URL "https://github.com/google/snappy.git" CACHE STRING "Url to Snappy git")
-set(SNAPPY_TAG "1.1.7" CACHE STRING "Git tag to build")
+set(SNAPPY_TAG "1.2.0" CACHE STRING "Git tag to build")
 set(SNAPPY_CMAKE_ARGS "-DCMAKE_TOOLCHAIN_FILE=${CMAKE_TOOLCHAIN_FILE}" -DSNAPPY_BUILD_TESTS=OFF)
 
 set(LEVELDB_URL "https://github.com/google/leveldb.git" CACHE STRING "URL to LevelDB git")
-set(LEVELDB_TAG "1.21" CACHE STRING "Git tag to build")
+set(LEVELDB_TAG "1.23" CACHE STRING "Git tag to build")
 set(LEVELDB_CMAKE_ARGS "-DCMAKE_TOOLCHAIN_FILE=${CMAKE_TOOLCHAIN_FILE}" -DLEVELDB_BUILD_TESTS=OFF -DLEVELDB_BUILD_BENCHMARKS=OFF)
 
 set(EXTERNAL_INSTALL_DIR ${CMAKE_CURRENT_BINARY_DIR}/external-install)
@@ -36,7 +36,7 @@ set (LEVELDB_REQUIRED_FLAGS
 ExternalProject_Add(leveldb_external
   GIT_REPOSITORY    ${LEVELDB_URL}
   GIT_TAG           ${LEVELDB_TAG}
-  PATCH_COMMAND     patch -p1 < ${CMAKE_CURRENT_SOURCE_DIR}/leveldb.compaction.patch
+  PATCH_COMMAND     patch --batch --dry-run --read-only=ignore --reverse --silent -p1 < ${CMAKE_CURRENT_SOURCE_DIR}/leveldb.compaction.patch && echo "Patch already applied" || patch --forward -p1 < ${CMAKE_CURRENT_SOURCE_DIR}/leveldb.compaction.patch
   CMAKE_ARGS        ${CMAKE_ARGS}
                     ${LEVELDB_CMAKE_ARGS}
                     "-DCMAKE_INSTALL_PREFIX=${EXTERNAL_INSTALL_DIR}"
diff --git a/main.cpp b/main.cpp
index e197699..2441395 100644
--- a/main.cpp
+++ b/main.cpp
@@ -23,6 +23,20 @@ static void dumpAllKeys(leveldb::DB* db, bool keysOnly) {
   }
 }
 
+#ifdef EMSCRIPTEN
+// note - this is an emscripten specific workaround to write binary to stdout
+// for some reason, doing an frwrite to stdout produces garbage, probably
+// because of utf-8 conversion ??
+EM_JS(void, to_stdout, (const char* buffer, size_t length), {
+    const array = new Uint8Array(length);
+    for (let i = 0; i < length; i++) {
+      array[i] = getValue(buffer + i, 'i8');
+    }
+
+    process.stdout.write(array);
+});
+#endif
+
 static bool dumpValue(leveldb::DB* db, const std::string& key) {
   auto iter = std::unique_ptr<leveldb::Iterator>{db->NewIterator({})};
   iter->Seek(key);
@@ -31,8 +45,12 @@ static bool dumpValue(leveldb::DB* db, const std::string& key) {
     return false;
   }
 
+#ifdef EMSCRIPTEN
+  to_stdout(iter->value().data(), iter->value().size());
+#else
   // use fwrite to make sure that \0 bytes are also written
   fwrite(iter->value().data(), 1, iter->value().size(), stdout);
+#endif
 
   return true;
 }