diff --git a/src/dom.ts b/src/dom.ts
index 672a0033..87271fef 100644
--- a/src/dom.ts
+++ b/src/dom.ts
@@ -1,5 +1,8 @@
 import { refKey } from "./utils";
 
+/**
+ * @internal
+ */
 export const isSafari = (): boolean => {
   const ua = navigator.userAgent.toLowerCase();
   return ua.indexOf("safari") > -1 && ua.indexOf("chrome") <= -1;
@@ -68,14 +71,23 @@ const getValueFromStyle = (style: CSSStyleDeclaration, key: string): number => {
   }
 };
 
+/**
+ * @internal
+ */
 export const getStyle = (e: Element) => getComputedStyle(e);
 
+/**
+ * @internal
+ */
 export const hasPercentageUnit = (
   widthOrHeight: React.CSSProperties["width"] | React.CSSProperties["height"]
 ): boolean => {
   return typeof widthOrHeight === "string" && widthOrHeight.endsWith("%");
 };
 
+/**
+ * @internal
+ */
 export const getVerticalPadding = (style: CSSStyleDeclaration): number => {
   return (
     getValueFromStyle(style, "padding-top") +
@@ -85,6 +97,9 @@ export const getVerticalPadding = (style: CSSStyleDeclaration): number => {
   );
 };
 
+/**
+ * @internal
+ */
 export const getHorizontalPadding = (style: CSSStyleDeclaration): number => {
   return (
     getValueFromStyle(style, "padding-left") +
@@ -94,6 +109,9 @@ export const getHorizontalPadding = (style: CSSStyleDeclaration): number => {
   );
 };
 
+/**
+ * @internal
+ */
 export const getPointedElement = (
   textarea: HTMLElement,
   backdrop: HTMLElement,
@@ -136,6 +154,9 @@ const dispatchMouseEvent = (
   target.dispatchEvent(new MouseEvent(type, init));
 };
 
+/**
+ * @internal
+ */
 export const dispatchClonedMouseEvent = (
   pointed: HTMLElement,
   e: MouseEvent
@@ -143,6 +164,9 @@ export const dispatchClonedMouseEvent = (
   dispatchMouseEvent(pointed, e.type, e);
 };
 
+/**
+ * @internal
+ */
 export const dispatchMouseMoveEvent = (
   pointed: HTMLElement | null,
   prevPointed: HTMLElement | null,
@@ -160,6 +184,9 @@ export const dispatchMouseMoveEvent = (
   }
 };
 
+/**
+ * @internal
+ */
 export const dispatchMouseOutEvent = (
   prevPointed: HTMLElement | null,
   e: MouseEvent
@@ -169,10 +196,16 @@ export const dispatchMouseOutEvent = (
   }
 };
 
+/**
+ * @internal
+ */
 export const stopPropagation = (event: React.MouseEvent) => {
   event.stopPropagation();
 };
 
+/**
+ * @internal
+ */
 export const syncBackdropStyle = (
   textarea: HTMLElement,
   backdrop: HTMLElement,
@@ -193,9 +226,12 @@ export const syncBackdropStyle = (
   textareaStyle.caretColor = style?.caretColor || caretColorRef[refKey];
 };
 
+/**
+ * @internal
+ */
 export const listenEvent = <
   E extends HTMLElement | Document,
-  K extends keyof GlobalEventHandlersEventMap
+  K extends keyof GlobalEventHandlersEventMap,
 >(
   el: E,
   key: K,
diff --git a/src/observer.ts b/src/observer.ts
index c0a04071..0af23fc0 100644
--- a/src/observer.ts
+++ b/src/observer.ts
@@ -10,13 +10,19 @@ import {
 } from "./dom";
 import { SelectionStore } from "./selection";
 
+/**
+ * @internal
+ */
 export type TextareaRect = [
   width: number,
   height: number,
   hPadding: number,
-  vPadding: number
+  vPadding: number,
 ];
 
+/**
+ * @internal
+ */
 export const createTextareaObserver = (
   textarea: HTMLTextAreaElement | HTMLInputElement,
   backdrop: HTMLDivElement,
diff --git a/src/regex.ts b/src/regex.ts
index 51485a59..bcb644d6 100644
--- a/src/regex.ts
+++ b/src/regex.ts
@@ -1,3 +1,6 @@
+/**
+ * @internal
+ */
 export const execReg = (reg: RegExp, text: string): RegExpExecArray[] => {
   const results: RegExpExecArray[] = [];
   let match: RegExpExecArray | null = null;
diff --git a/src/selection.ts b/src/selection.ts
index 64ece6b4..f860a250 100644
--- a/src/selection.ts
+++ b/src/selection.ts
@@ -1,7 +1,13 @@
 import { refKey } from "./utils";
 
+/**
+ * @internal
+ */
 export type SelectionRange = [number | null, number | null];
 
+/**
+ * @internal
+ */
 export const initSelectionStore = (
   ref: React.RefObject<HTMLTextAreaElement | HTMLInputElement>,
   onSelectionUpdate: (range: SelectionRange) => void
@@ -49,4 +55,7 @@ export const initSelectionStore = (
   return handle;
 };
 
+/**
+ * @internal
+ */
 export type SelectionStore = ReturnType<typeof initSelectionStore>;
diff --git a/src/useIsomorphicLayoutEffect.ts b/src/useIsomorphicLayoutEffect.ts
index 4985c224..8090025b 100644
--- a/src/useIsomorphicLayoutEffect.ts
+++ b/src/useIsomorphicLayoutEffect.ts
@@ -1,5 +1,8 @@
 import { useEffect, useLayoutEffect } from "react";
 
-// https://gist.github.com/gaearon/e7d97cdf38a2907924ea12e4ebdf3c85
+/**
+ * https://gist.github.com/gaearon/e7d97cdf38a2907924ea12e4ebdf3c85
+ * @internal
+ */
 export const useIsomorphicLayoutEffect =
   typeof window !== "undefined" ? useLayoutEffect : useEffect;
diff --git a/src/useStatic.ts b/src/useStatic.ts
index 3cdc18b3..c8433918 100644
--- a/src/useStatic.ts
+++ b/src/useStatic.ts
@@ -1,6 +1,9 @@
 import { useRef } from "react";
 import { refKey } from "./utils";
 
+/**
+ * @internal
+ */
 export const useStatic = <T>(init: () => T): T => {
   const ref = useRef<T>();
   return ref[refKey] || (ref[refKey] = init());
diff --git a/src/utils.tsx b/src/utils.tsx
index 69790dde..72fa02e6 100644
--- a/src/utils.tsx
+++ b/src/utils.tsx
@@ -1,6 +1,12 @@
+/**
+ * @internal
+ */
 export const refKey = "current";
 
-// for caret position detection
+/**
+ * for caret position detection
+ * @internal
+ */
 export const CARET_DETECTOR = (
   <span style={{ color: "transparent" }}>{"\u200b"}</span>
 );
diff --git a/tsconfig.json b/tsconfig.json
index d7673df1..20920d15 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -22,7 +22,8 @@
     "noFallthroughCasesInSwitch": true,
     "allowUnreachableCode": false,
     "allowUnusedLabels": false,
-    "exactOptionalPropertyTypes": true
+    "exactOptionalPropertyTypes": true,
+    "stripInternal": true
   },
   "include": ["src"],
   "exclude": ["node_modules"]