diff --git a/.github/workflows/test-multiple-builds.yml b/.github/workflows/test-multiple-builds.yml
index 404b1687..20ed0ed5 100644
--- a/.github/workflows/test-multiple-builds.yml
+++ b/.github/workflows/test-multiple-builds.yml
@@ -12,7 +12,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        build: [cjs, esm, umd] # [cjs, esm, umd, system]
+        build: [cjs, esm]
         env: [development] # [development, production]
     steps:
       - uses: actions/checkout@v2
@@ -44,18 +44,6 @@ jobs:
           sed -i~ "1s/^/import.meta.env=import.meta.env||{};import.meta.env.MODE='${NODE_ENV}';/" tests/*.ts tests/*.tsx
         env:
           NODE_ENV: ${{ matrix.env }}
-      - name: Patch for UMD
-        if: ${{ matrix.build == 'umd' }}
-        run: |
-          sed -i~ "s/<rootDir>\/src\(.*\)\.ts/<rootDir>\/dist\/umd\1.${NODE_ENV}.js/" package.json
-        env:
-          NODE_ENV: ${{ matrix.env }}
-      - name: Patch for SystemJS
-        if: ${{ matrix.build == 'system' }}
-        run: |
-          sed -i~ "s/<rootDir>\/src\(.*\)\.ts/<rootDir>\/dist\/system\1.${NODE_ENV}.js/" package.json
-        env:
-          NODE_ENV: ${{ matrix.env }}
       - name: Test ${{ matrix.build }} ${{ matrix.env }}
         run: |
           yarn test:ci
diff --git a/babel.config.js b/babel.config.js
deleted file mode 100644
index fa15c8a7..00000000
--- a/babel.config.js
+++ /dev/null
@@ -1,28 +0,0 @@
-module.exports = (api, targets) => {
-  // https://babeljs.io/docs/en/config-files#config-function-api
-  const isTestEnv = api.env('test')
-
-  return {
-    babelrc: false,
-    ignore: ['./node_modules'],
-    presets: [
-      [
-        '@babel/preset-env',
-        {
-          loose: true,
-          modules: isTestEnv ? 'commonjs' : false,
-          targets: isTestEnv ? { node: 'current' } : targets,
-        },
-      ],
-    ],
-    plugins: [
-      [
-        '@babel/plugin-transform-react-jsx',
-        {
-          runtime: 'automatic',
-        },
-      ],
-      ['@babel/plugin-transform-typescript', { isTSX: true }],
-    ],
-  }
-}
diff --git a/package.json b/package.json
index 9c80940c..08df6eb7 100644
--- a/package.json
+++ b/package.json
@@ -116,7 +116,6 @@
     "@rollup/plugin-babel": "^6.0.4",
     "@rollup/plugin-node-resolve": "^15.2.3",
     "@rollup/plugin-replace": "^5.0.5",
-    "@rollup/plugin-terser": "^0.4.4",
     "@rollup/plugin-typescript": "^11.1.5",
     "@testing-library/react": "^14.0.0",
     "@types/jsdom": "^21.1.4",
diff --git a/rollup.config.js b/rollup.config.js
index 9d12aee4..1534ddad 100644
--- a/rollup.config.js
+++ b/rollup.config.js
@@ -3,10 +3,8 @@ const alias = require('@rollup/plugin-alias')
 const babelPlugin = require('@rollup/plugin-babel')
 const resolve = require('@rollup/plugin-node-resolve')
 const replace = require('@rollup/plugin-replace')
-const terser = require('@rollup/plugin-terser')
 const typescript = require('@rollup/plugin-typescript')
 const { default: esbuild } = require('rollup-plugin-esbuild')
-const createBabelConfig = require('./babel.config.js')
 
 const extensions = ['.js', '.ts', '.tsx']
 const { root } = path.parse(process.cwd())
@@ -23,7 +21,13 @@ function external(id) {
 
 function getBabelOptions(targets) {
   return {
-    ...createBabelConfig({ env: (env) => env === 'build' }, targets),
+    babelrc: false,
+    ignore: ['./node_modules'],
+    presets: [['@babel/preset-env', { loose: true, modules: false, targets }]],
+    plugins: [
+      ['@babel/plugin-transform-react-jsx', { runtime: 'automatic' }],
+      ['@babel/plugin-transform-typescript', { isTSX: true }],
+    ],
     extensions,
     comments: false,
     babelHelpers: 'bundled',
@@ -98,64 +102,6 @@ function createCommonJSConfig(input, output) {
   }
 }
 
-function createUMDConfig(input, output, env) {
-  let name = 'valtio'
-  const fileName = output.slice('dist/umd/'.length)
-  const capitalize = (s) => s.slice(0, 1).toUpperCase() + s.slice(1)
-  if (fileName !== 'index') {
-    name += fileName.replace(/(\w+)\W*/g, (_, p) => capitalize(p))
-  }
-  return {
-    input,
-    output: {
-      file: `${output}.${env}.js`,
-      format: 'umd',
-      name,
-      globals: {
-        react: 'React',
-        'valtio/vanilla': 'valtioVanilla',
-        'valtio/utils': 'valtioUtils',
-        'valtio/react': 'valtioReact',
-        'valtio/vanilla/utils': 'valtioVanillaUtils',
-        'valtio/react/utils': 'valtioReactUtils',
-      },
-    },
-    external,
-    plugins: [
-      alias({ entries: entries.filter((e) => !e.find.test(input)) }),
-      resolve({ extensions }),
-      replace({
-        'import.meta.env?.MODE': JSON.stringify(env),
-        delimiters: ['\\b', '\\b(?!(\\.|/))'],
-        preventAssignment: true,
-      }),
-      babelPlugin(getBabelOptions({ ie: 11 })),
-      ...(env === 'production' ? [terser()] : []),
-    ],
-  }
-}
-
-function createSystemConfig(input, output, env) {
-  return {
-    input,
-    output: {
-      file: `${output}.${env}.js`,
-      format: 'system',
-    },
-    external,
-    plugins: [
-      alias({ entries: entries.filter((e) => !e.find.test(input)) }),
-      resolve({ extensions }),
-      replace({
-        'import.meta.env?.MODE': JSON.stringify(env),
-        delimiters: ['\\b', '\\b(?!(\\.|/))'],
-        preventAssignment: true,
-      }),
-      getEsbuild('node12', env),
-    ],
-  }
-}
-
 module.exports = function (args) {
   let c = Object.keys(args).find((key) => key.startsWith('config-'))
   if (c) {
@@ -167,10 +113,6 @@ module.exports = function (args) {
     ...(c === 'index' ? [createDeclarationConfig(`src/${c}.ts`, 'dist')] : []),
     createCommonJSConfig(`src/${c}.ts`, `dist/${c}`),
     createESMConfig(`src/${c}.ts`, `dist/esm/${c}.mjs`),
-    createUMDConfig(`src/${c}.ts`, `dist/umd/${c}`, 'development'),
-    createUMDConfig(`src/${c}.ts`, `dist/umd/${c}`, 'production'),
-    createSystemConfig(`src/${c}.ts`, `dist/system/${c}`, 'development'),
-    createSystemConfig(`src/${c}.ts`, `dist/system/${c}`, 'production'),
   ]
 }