diff --git a/package.json b/package.json
index 48a6a9b..481edd1 100644
--- a/package.json
+++ b/package.json
@@ -36,6 +36,7 @@
   "files": [
     "bin/emglken.js",
     "build/*.js",
+    "build/*.json",
     "build/*.wasm",
     "src/*.js"
   ]
diff --git a/src/build.sh b/src/build.sh
index d76f5ee..490c447 100755
--- a/src/build.sh
+++ b/src/build.sh
@@ -15,4 +15,6 @@ docker run --rm -t \
     /bin/bash -c " \\
         emcmake cmake -DCMAKE_BUILD_TYPE=Release -S . -B build; \\
         emmake make -j$(nproc) --no-print-directory -C build \\
-    "
\ No newline at end of file
+    "
+
+./tools/write-file-sizes.js
\ No newline at end of file
diff --git a/tools/write-file-sizes.js b/tools/write-file-sizes.js
new file mode 100755
index 0000000..60a31c8
--- /dev/null
+++ b/tools/write-file-sizes.js
@@ -0,0 +1,18 @@
+#!/usr/bin/env node
+
+// Write build/file-sizes.json
+
+import * as fs from 'fs'
+import {dirname, resolve} from 'path'
+import {fileURLToPath} from 'url'
+
+const results = {};
+
+const build_path = resolve(dirname(fileURLToPath(import.meta.url)), '../build')
+for (const file of fs.readdirSync(build_path)) {
+    if (file.endsWith('.js') || file.endsWith('.wasm')) {
+        results[file] = fs.statSync(resolve(build_path, file)).size
+    }
+}
+
+fs.writeFileSync(resolve(build_path, 'file-sizes.json'), JSON.stringify(results))
\ No newline at end of file