diff --git a/index.js b/index.js
index 2350cbf..f5d5467 100644
--- a/index.js
+++ b/index.js
@@ -1,11 +1,7 @@
-'use strict'
-
-var visit = require('unist-util-visit')
-var toString = require('nlcst-to-string')
-var literal = require('nlcst-is-literal')
-var rules = require('./index.json')
-
-module.exports = contractions
+import visit from 'unist-util-visit'
+import toString from 'nlcst-to-string'
+import literal from 'nlcst-is-literal'
+import {list} from './list.js'
 
 // Rules.
 var source = 'retext-contractions'
@@ -23,7 +19,7 @@ var own = {}.hasOwnProperty
 var data = initialize()
 
 // Check contractions use.
-function contractions(options) {
+export default function retextContractions(options) {
   var ignore = options && options.allowLiterals
   var straight = options && options.straight
 
@@ -93,8 +89,8 @@ function initialize() {
   var key
   var value
 
-  for (key in rules) {
-    value = rules[key]
+  for (key in list) {
+    value = list[key]
     result[key] = value
 
     // Add upper- and sentence case as well.
diff --git a/index.json b/index.json
deleted file mode 100644
index 0ad3315..0000000
--- a/index.json
+++ /dev/null
@@ -1,63 +0,0 @@
-{
-  "aint": "ain't",
-  "arent": "aren't",
-  "couldnt": "couldn't",
-  "didnt": "didn't",
-  "doesnt": "doesn't",
-  "dont": "don't",
-  "hadnt": "hadn't",
-  "hasnt": "hasn't",
-  "havent": "haven't",
-  "hed": "he'd",
-  "hes": "he's",
-  "howd": "how'd",
-  "hows": "how's",
-  "howll": "how'll",
-  "Id": "I'd",
-  "Im": "I'm",
-  "Ive": "I've",
-  "isnt": "isn't",
-  "mightnt": "mightn't",
-  "mustve": "must've",
-  "mustnt": "mustn't",
-  "neednt": "needn't",
-  "oclock": "o'clock",
-  "shant": "shan't",
-  "shes": "she's",
-  "shouldve": "should've",
-  "shouldnt": "shouldn't",
-  "thatd": "that'd",
-  "thats": "that's",
-  "thered": "there'd",
-  "theres": "there's",
-  "therere": "there're",
-  "theyd": "they'd",
-  "theyll": "they'll",
-  "theyre": "they're",
-  "theyve": "they've",
-  "tis": "'tis",
-  "twas": "'twas",
-  "twere": "'twere",
-  "wasnt": "wasn't",
-  "weve": "we've",
-  "werent": "weren't",
-  "whatll": "what'll",
-  "whatre": "what're",
-  "whats": "what's",
-  "whatve": "what've",
-  "whens": "when's",
-  "wheres": "where's",
-  "whereve": "where've",
-  "whod": "who'd",
-  "wholl": "who'll",
-  "whos": "who's",
-  "whove": "who've",
-  "whys": "why's",
-  "wouldve": "would've",
-  "wouldnt": "wouldn't",
-  "yall": "y'all",
-  "youd": "you'd",
-  "youll": "you'll",
-  "youre": "you're",
-  "youve": "you've"
-}
diff --git a/list.js b/list.js
new file mode 100644
index 0000000..b3a2e33
--- /dev/null
+++ b/list.js
@@ -0,0 +1,63 @@
+export const list = {
+  aint: "ain't",
+  arent: "aren't",
+  couldnt: "couldn't",
+  didnt: "didn't",
+  doesnt: "doesn't",
+  dont: "don't",
+  hadnt: "hadn't",
+  hasnt: "hasn't",
+  havent: "haven't",
+  hed: "he'd",
+  hes: "he's",
+  howd: "how'd",
+  hows: "how's",
+  howll: "how'll",
+  Id: "I'd",
+  Im: "I'm",
+  Ive: "I've",
+  isnt: "isn't",
+  mightnt: "mightn't",
+  mustve: "must've",
+  mustnt: "mustn't",
+  neednt: "needn't",
+  oclock: "o'clock",
+  shant: "shan't",
+  shes: "she's",
+  shouldve: "should've",
+  shouldnt: "shouldn't",
+  thatd: "that'd",
+  thats: "that's",
+  thered: "there'd",
+  theres: "there's",
+  therere: "there're",
+  theyd: "they'd",
+  theyll: "they'll",
+  theyre: "they're",
+  theyve: "they've",
+  tis: "'tis",
+  twas: "'twas",
+  twere: "'twere",
+  wasnt: "wasn't",
+  weve: "we've",
+  werent: "weren't",
+  whatll: "what'll",
+  whatre: "what're",
+  whats: "what's",
+  whatve: "what've",
+  whens: "when's",
+  wheres: "where's",
+  whereve: "where've",
+  whod: "who'd",
+  wholl: "who'll",
+  whos: "who's",
+  whove: "who've",
+  whys: "why's",
+  wouldve: "would've",
+  wouldnt: "wouldn't",
+  yall: "y'all",
+  youd: "you'd",
+  youll: "you'll",
+  youre: "you're",
+  youve: "you've"
+}
diff --git a/package.json b/package.json
index eb81651..73f5023 100644
--- a/package.json
+++ b/package.json
@@ -23,9 +23,12 @@
     "Titus Wormer <tituswormer@gmail.com> (https://wooorm.com)",
     "Sylvan Swierkosz <sswierkosz@gmail.com>"
   ],
+  "sideEffects": false,
+  "type": "module",
+  "main": "index.js",
   "files": [
     "index.js",
-    "index.json"
+    "list.js"
   ],
   "dependencies": {
     "nlcst-is-literal": "^1.0.0",
@@ -39,7 +42,7 @@
     "remark-preset-wooorm": "^8.0.0",
     "retext": "^7.0.0",
     "tape": "^5.0.0",
-    "xo": "^0.37.0"
+    "xo": "^0.39.0"
   },
   "scripts": {
     "format": "remark . -qfo && prettier . -w --loglevel warn && xo --fix",
@@ -57,8 +60,9 @@
   },
   "xo": {
     "prettier": true,
-    "esnext": false,
     "rules": {
+      "no-var": "off",
+      "prefer-arrow-callback": "off",
       "unicorn/no-array-callback-reference": "off",
       "guard-for-in": "off"
     }
diff --git a/test.js b/test.js
index 64b128d..9dc2f73 100644
--- a/test.js
+++ b/test.js
@@ -1,8 +1,6 @@
-'use strict'
-
-var test = require('tape')
-var retext = require('retext')
-var contractions = require('.')
+import test from 'tape'
+import retext from 'retext'
+import contractions from './index.js'
 
 test('contractions(value)', function (t) {
   t.deepEqual(