diff --git a/.gitignore b/.gitignore
index 7f93ef7..735f4af 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,8 +1,5 @@
 .DS_Store
 *.log
-.nyc_output/
 coverage/
 node_modules/
-unist-util-visit-children.js
-unist-util-visit-children.min.js
 yarn.lock
diff --git a/.prettierignore b/.prettierignore
index 5e770e4..cebe81f 100644
--- a/.prettierignore
+++ b/.prettierignore
@@ -1,5 +1,2 @@
 coverage/
-unist-util-visit-children.js
-unist-util-visit-children.min.js
-*.json
 *.md
diff --git a/index.js b/index.js
index 0b15d41..bf52b70 100644
--- a/index.js
+++ b/index.js
@@ -1,8 +1,4 @@
-'use strict'
-
-module.exports = visitChildren
-
-function visitChildren(callback) {
+export function visitChildren(callback) {
   return visitor
 
   // Visit `parent`, invoking `callback` for each child.
diff --git a/package.json b/package.json
index b603187..ed58cf0 100644
--- a/package.json
+++ b/package.json
@@ -21,33 +21,25 @@
   "contributors": [
     "Titus Wormer <tituswormer@gmail.com> (https://wooorm.com)"
   ],
+  "sideEffects": false,
+  "type": "module",
+  "main": "index.js",
   "files": [
     "index.js"
   ],
   "devDependencies": {
-    "browserify": "^17.0.0",
-    "nyc": "^15.0.0",
+    "c8": "^7.0.0",
     "prettier": "^2.0.0",
     "remark-cli": "^9.0.0",
     "remark-preset-wooorm": "^8.0.0",
     "tape": "^5.0.0",
-    "tinyify": "^3.0.0",
     "xo": "^0.38.0"
   },
   "scripts": {
     "format": "remark . -qfo && prettier . -w --loglevel warn && xo --fix",
-    "build-bundle": "browserify . -s unistUtilVisitChildren -o unist-util-visit-children.js",
-    "build-mangle": "browserify . -s unistUtilVisitChildren -o unist-util-visit-children.min.js -p tinyify",
-    "build": "npm run build-bundle && npm run build-mangle",
-    "test-api": "node test",
-    "test-coverage": "nyc --reporter lcov tape test.js",
-    "test": "npm run format && npm run build && npm run test-coverage"
-  },
-  "nyc": {
-    "check-coverage": true,
-    "lines": 100,
-    "functions": 100,
-    "branches": 100
+    "test-api": "node test.js",
+    "test-coverage": "c8 --check-coverage --branches 100 --functions 100 --lines 100 --statements 100 --reporter lcov node test.js",
+    "test": "npm run format && npm run test-coverage"
   },
   "prettier": {
     "tabWidth": 2,
@@ -59,13 +51,10 @@
   },
   "xo": {
     "prettier": true,
-    "esnext": false,
     "rules": {
-      "guard-for-in": "off"
-    },
-    "ignores": [
-      "unist-util-visit-children.js"
-    ]
+      "no-var": "off",
+      "prefer-arrow-callback": "off"
+    }
   },
   "remarkConfig": {
     "plugins": [
diff --git a/readme.md b/readme.md
index 0390085..80a588e 100644
--- a/readme.md
+++ b/readme.md
@@ -12,6 +12,9 @@
 
 ## Install
 
+This package is [ESM only](https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c):
+Node 12+ is needed to use it and it must be `import`ed instead of `require`d.
+
 [npm][]:
 
 ```sh
@@ -21,8 +24,8 @@ npm install unist-util-visit-children
 ## Use
 
 ```js
-var u = require('unist-builder')
-var visitChildren = require('unist-util-visit-children')
+import u from 'unist-builder'
+import {visitChildren} from 'unist-util-visit-children'
 
 var visit = visitChildren(function(node) {
   console.log(node)
@@ -55,6 +58,9 @@ Yields:
 
 ## API
 
+This package exports the following identifiers: `visitChildren`.
+There is no default export.
+
 ### `visit = visitChildren(visitor)`
 
 Wrap [`visitor`][visitor] to be invoked for each [child][] in the nodes later
diff --git a/test.js b/test.js
index bd184de..c0ea4ee 100644
--- a/test.js
+++ b/test.js
@@ -1,9 +1,7 @@
-'use strict'
+import test from 'tape'
+import {visitChildren} from './index.js'
 
-var test = require('tape')
-var visitChildren = require('.')
-
-var noop = Function.prototype
+function noop() {}
 
 test('visitChildren()', function (t) {
   t.throws(