diff --git a/packages/expo/package.json b/packages/expo/package.json
index e8c5e1a06ab..843da5e5571 100644
--- a/packages/expo/package.json
+++ b/packages/expo/package.json
@@ -101,10 +101,10 @@
     "app.plugin.d.ts"
   ],
   "scripts": {
-    "build": "tsup",
+    "build": "tsdown",
     "build:declarations": "tsc -p tsconfig.declarations.json",
     "clean": "rimraf ./dist",
-    "dev": "tsup --watch",
+    "dev": "tsdown --watch",
     "dev:pub": "pnpm dev -- --env.publish",
     "format": "node ../../scripts/format-package.mjs",
     "format:check": "node ../../scripts/format-package.mjs --check",
diff --git a/packages/expo/src/polyfills/base64Polyfill.ts b/packages/expo/src/polyfills/base64Polyfill.ts
index 2d9bd89b610..f77ed0d8c12 100644
--- a/packages/expo/src/polyfills/base64Polyfill.ts
+++ b/packages/expo/src/polyfills/base64Polyfill.ts
@@ -3,11 +3,11 @@ import { decode, encode } from 'base-64';
 import { isHermes } from '../utils';
 
 // See Default Expo 51 engine Hermes' issue: https://github.com/facebook/hermes/issues/1379
-if (!global.btoa || isHermes()) {
-  global.btoa = encode;
+if (!globalThis.btoa || isHermes()) {
+  globalThis.btoa = encode;
 }
 
 // See Default Expo 51 engine Hermes' issue: https://github.com/facebook/hermes/issues/1379
-if (!global.atob || isHermes()) {
-  global.atob = decode;
+if (!globalThis.atob || isHermes()) {
+  globalThis.atob = decode;
 }
diff --git a/packages/expo/tsconfig.json b/packages/expo/tsconfig.json
index 46556b4b9f3..5510c6beb95 100644
--- a/packages/expo/tsconfig.json
+++ b/packages/expo/tsconfig.json
@@ -1,8 +1,7 @@
 {
   "compilerOptions": {
     "outDir": "dist",
-    "baseUrl": ".",
-    "lib": ["es6", "dom"],
+    "lib": ["es2019", "dom"],
     "jsx": "react-jsx",
     "module": "NodeNext",
     "moduleResolution": "NodeNext",
diff --git a/packages/expo/tsup.config.ts b/packages/expo/tsdown.config.mts
similarity index 57%
rename from packages/expo/tsup.config.ts
rename to packages/expo/tsdown.config.mts
index 4b166fd82ab..5ab8a07366e 100644
--- a/packages/expo/tsup.config.ts
+++ b/packages/expo/tsdown.config.mts
@@ -1,9 +1,9 @@
-import type { Options } from 'tsup';
-import { defineConfig } from 'tsup';
+import type { Options } from 'tsdown';
+import { defineConfig } from 'tsdown';
 
-import { runAfterLast } from '../../scripts/utils';
-import { version as clerkJsVersion } from '../clerk-js/package.json';
-import { name, version } from './package.json';
+import { runAfterLast } from '../../scripts/utils.ts';
+import clerkJsPkgJson from '../clerk-js/package.json' with { type: 'json' };
+import pkgJson from './package.json' with { type: 'json' };
 
 export default defineConfig(overrideOptions => {
   const isWatch = !!overrideOptions.watch;
@@ -17,11 +17,10 @@ export default defineConfig(overrideOptions => {
     clean: true,
     minify: false,
     sourcemap: true,
-    legacyOutput: true,
     define: {
-      PACKAGE_NAME: `"${name}"`,
-      PACKAGE_VERSION: `"${version}"`,
-      JS_PACKAGE_VERSION: `"${clerkJsVersion}"`,
+      PACKAGE_NAME: `"${pkgJson.name}"`,
+      PACKAGE_VERSION: `"${pkgJson.version}"`,
+      JS_PACKAGE_VERSION: `"${clerkJsPkgJson.version}"`,
       __DEV__: `${isWatch}`,
     },
   };
diff --git a/scripts/utils.ts b/scripts/utils.ts
index 9b0efba0b31..de4f280bc18 100644
--- a/scripts/utils.ts
+++ b/scripts/utils.ts
@@ -1,4 +1,4 @@
-import type { Options } from 'tsup';
+import type { Options } from 'tsdown';
 
 export const runAfterLast =
   (commands: Array<string | false>) =>