diff --git a/.changeset/afraid-seas-confess.md b/.changeset/afraid-seas-confess.md
new file mode 100644
index 0000000..85cfeb7
--- /dev/null
+++ b/.changeset/afraid-seas-confess.md
@@ -0,0 +1,5 @@
+---
+'@dimensiondev/stego-js': patch
+---
+
+improve typescript definition
diff --git a/package.json b/package.json
index af3d4b0..a5d95b9 100644
--- a/package.json
+++ b/package.json
@@ -11,6 +11,7 @@
   "module": "./esm/node.js",
   "browser": "./esm/dom.js",
   "bin": "./esm/cli/cli.js",
+  "types": "./esm/dom.js",
   "scripts": {
     "build": "pnpm run build:umd && pnpm run build:dist",
     "build:dist": "tsc -b ./tsconfig.json ./tests/tsconfig.json",
diff --git a/src/dom.ts b/src/dom.ts
index 494f5d0..0fc2257 100644
--- a/src/dom.ts
+++ b/src/dom.ts
@@ -2,7 +2,7 @@ import { createAPI } from './utils/expose.js'
 import { getImageType } from './utils/helper.js'
 import { preprocessImage } from './utils/image.js'
 
-export { getImageType }
+export { getImageType } from './utils/helper.js'
 export * from './utils/types.js'
 export * from './constant.js'
 
diff --git a/src/module.d.ts b/src/module.d.ts
deleted file mode 100644
index 40ad698..0000000
--- a/src/module.d.ts
+++ /dev/null
@@ -1,6 +0,0 @@
-// declarations for external modules
-declare namespace NodeJS {
-  export interface ProcessEnv {
-    PLATFORM: 'node' | 'dom'
-  }
-}
diff --git a/src/node.ts b/src/node.ts
index dbce4fb..5ed3064 100644
--- a/src/node.ts
+++ b/src/node.ts
@@ -1,10 +1,9 @@
 import { JsColorType, Transformer } from '@napi-rs/image'
 import { randomFillSync } from 'crypto'
 import { createAPI } from './utils/expose.js'
-import { getImageType } from './utils/helper.js'
 import { preprocessImage } from './utils/image.js'
 
-export { getImageType }
+export { getImageType } from './utils/helper.js'
 export * from './utils/types.js'
 export * from './constant.js'