diff --git a/middleware/load-options.js b/lib/load-options.js
similarity index 54%
rename from middleware/load-options.js
rename to lib/load-options.js
index e72d7ad7..f3e43984 100644
--- a/middleware/load-options.js
+++ b/lib/load-options.js
@@ -11,10 +11,10 @@ const getUrlParts = url => {
   return url.slice(1).split('/')
 }
 
-module.exports = (request, response, next) => {
-  const urlParts = getUrlParts(request.url)
+const loadOptions = url => {
+  const urlParts = getUrlParts(url)
 
-  response.locals.options = {
+  const options = {
     format: 'html',
     startYear: null,
     endYear: currentYear
@@ -23,21 +23,23 @@ module.exports = (request, response, next) => {
   for (const urlPart of urlParts) {
     if (yearRegex.test(urlPart)) {
       if (urlPart.startsWith('@')) {
-        response.locals.options.pinnedYear = Number.parseInt(urlPart.slice(1))
+        options.pinnedYear = Number.parseInt(urlPart.slice(1), 10)
       } else {
-        response.locals.options.startYear = Number.parseInt(urlPart)
+        options.startYear = Number.parseInt(urlPart, 10)
       }
     } else if (yearRangeRegex.test(urlPart)) {
       const [startYear, endYear] = urlPart.match(yearRangeRegex).slice(1)
 
-      response.locals.options.startYear = Number.parseInt(startYear)
-      response.locals.options.endYear = Number.parseInt(endYear)
+      options.startYear = Number.parseInt(startYear, 10)
+      options.endYear = Number.parseInt(endYear, 10)
     } else if (urlPart.startsWith('license')) {
-      response.locals.options.format = urlPart.split('.')[1].trim()
+      options.format = urlPart.split('.')[1].trim()
     } else if (urlPart.startsWith('+')) {
-      response.locals.options.license = urlPart.slice(1).toUpperCase()
+      options.license = urlPart.slice(1).toUpperCase()
     }
   }
 
-  next()
+  return options
 }
+
+export default loadOptions
diff --git a/lib/load-user.js b/lib/load-user.js
new file mode 100644
index 00000000..acb3fc7b
--- /dev/null
+++ b/lib/load-user.js
@@ -0,0 +1,26 @@
+import {fileURLToPath} from 'node:url'
+import path, {dirname} from 'node:path'
+import loadJsonFile from 'load-json-file'
+
+const directoryName = dirname(fileURLToPath(import.meta.url))
+
+const loadUser = async hostname => {
+  const [id] = hostname.split('.')
+
+  const user = {
+    copyright: '<copyright holders>' // Fallback
+  }
+
+  try {
+    return {
+      ...user,
+      ...await loadJsonFile(path.join(directoryName, '..', 'users', `${id}.json`))
+    }
+  } catch (error) {
+    if (error.code !== 'ENOENT') {
+      throw error
+    }
+  }
+}
+
+export default loadUser
diff --git a/middleware/load-user.js b/middleware/load-user.js
deleted file mode 100644
index 9d602abb..00000000
--- a/middleware/load-user.js
+++ /dev/null
@@ -1,33 +0,0 @@
-const path = require('path')
-const loadJsonFile = require('load-json-file')
-
-module.exports = async (request, response, next) => {
-  const id = request.hostname.split('.')[0]
-
-  if (request.method.toUpperCase() !== 'GET') {
-    return next()
-  }
-
-  // Otherwise load up the user json file
-  response.locals.user = {
-    copyright: '<copyright holders>'
-  }
-
-  try {
-    response.locals.user = {
-      ...response.locals.user,
-      ...await loadJsonFile(path.join(__dirname, '..', 'users', `${id}.json`))
-    }
-  } catch ({ code, message }) {
-    if (code !== 'ENOENT') {
-      response
-        .code(500)
-        .send(
-          `An internal error occurred - open an issue on https://github.com/remy/mit-license with the following information: ${message}`
-        )
-      return
-    }
-  }
-
-  next()
-}
diff --git a/package.json b/package.json
index 589b5a3a..fc39e38f 100644
--- a/package.json
+++ b/package.json
@@ -2,6 +2,7 @@
   "name": "mit-licence",
   "description": "Hosted MIT License with details controlled through this repo",
   "private": true,
+  "type": "module",
   "version": "2.0.0",
   "main": "server.js",
   "repository": {
@@ -17,42 +18,45 @@
     "dev": "nodemon .",
     "serve": "node server.js",
     "test": "node test.js",
-    "lint": "standard"
+    "lint": "xo"
   },
   "bugs": {
     "url": "https://github.com/remy/mit-license/issues"
   },
   "license": "MIT",
   "dependencies": {
-    "@octokit/rest": "^18.0.6",
-    "@sindresorhus/is": "^3.1.2",
+    "@octokit/rest": "^18.5.3",
+    "@sindresorhus/is": "^4.0.1",
     "any-size": "^1.2.0",
     "btoa": "^1.2.1",
     "cors": "^2.8.5",
     "create-html-element": "^3.0.0",
-    "ejs": "^3.1.5",
-    "escape-goat": "^3.0.0",
+    "ejs": "^3.1.6",
+    "escape-goat": "^4.0.0",
     "express": "^4.17.1",
     "express-minify": "^1.0.0",
-    "gravatar-url": "^3.1.0",
+    "gravatar-url": "^4.0.0",
     "html-text": "^1.0.1",
     "load-json-file": "^6.2.0",
     "path-exists": "^4.0.0",
     "postcss-middleware": "^1.1.4",
     "postcss-preset-env": "^6.7.0",
+    "read-pkg": "^6.0.0",
     "serve-favicon": "^2.5.0",
     "temp-dir": "^2.0.0",
     "write-json-file": "^4.3.0",
     "yn": "^4.0.0"
   },
   "devDependencies": {
+    "@babel/eslint-parser": "^7.14.3",
+    "@babel/plugin-syntax-top-level-await": "^7.12.13",
     "css": "^3.0.0",
     "file-ext": "^1.0.0",
-    "has-flag": "^4.0.0",
+    "has-flag": "^5.0.0",
     "husky": "^4.3.0",
-    "nodemon": "^2.0.4",
+    "nodemon": "^2.0.7",
     "path-extra": "^4.3.0",
-    "standard": "^14.3.4"
+    "xo": "^0.40.1"
   },
   "resolutions": {
     "postcss-middleware/vinyl-fs/glob-stream/micromatch/braces": "^3.0.2"
@@ -62,5 +66,18 @@
       "pre-commit": "npm run lint",
       "pre-push": "npm test"
     }
+  },
+  "xo": {
+    "space": 2,
+    "semicolon": false,
+    "parser": "@babel/eslint-parser",
+    "parserOptions": {
+      "requireConfigFile": false,
+      "babelOptions": {
+          "plugins": [
+            "@babel/plugin-syntax-top-level-await"
+          ]
+      }
+    }
   }
 }
diff --git a/routes/get.js b/routes/get.js
index 284940ea..70faac79 100644
--- a/routes/get.js
+++ b/routes/get.js
@@ -1,10 +1,16 @@
-const path = require('path')
-const { htmlEscape, htmlUnescape } = require('escape-goat')
-const stripHtml = require('html-text')
-const is = require('@sindresorhus/is')
-const getGravatarUrl = require('gravatar-url')
-const createHtmlElement = require('create-html-element')
-const { renderFile } = require('ejs')
+import {fileURLToPath} from 'node:url'
+import path, {dirname} from 'node:path'
+import {htmlEscape, htmlUnescape} from 'escape-goat'
+import stripHtml from 'html-text'
+import is from '@sindresorhus/is'
+import getGravatarUrl from 'gravatar-url'
+import createHtmlElement from 'create-html-element'
+import {renderFile} from 'ejs'
+
+import loadUser from '../lib/load-user.js'
+import loadOptions from '../lib/load-options.js'
+
+const directoryName = dirname(fileURLToPath(import.meta.url))
 
 const getCopyrightName = (user, isPlainText) => {
   if (is.string(user)) {
@@ -53,9 +59,24 @@ const getGravatarEmail = user => {
 
 const removeFalsy = array => array.filter(Boolean)
 
-module.exports = async (_, response) => {
-  const { user, options } = response.locals
-  const isPlainText = options.format !== 'html'
+const getRoute = async (request, response) => {
+  let user
+  try {
+    user = await loadUser(request.hostname)
+  } catch ({message}) {
+    response
+      .status(500)
+      .send(`An internal error occurred - open an issue on https://github.com/remy/mit-license with the following information: ${message}`)
+    return
+  }
+
+  const options = loadOptions(request.url)
+  const year = options.pinnedYear ?
+    options.pinnedYear :
+    removeFalsy([options.startYear, options.endYear]).join('-')
+  const license = (options.license || user.license || 'MIT').toUpperCase()
+  const format = options.format || user.format || 'html'
+  const isPlainText = format !== 'html'
 
   let name
 
@@ -85,21 +106,15 @@ module.exports = async (_, response) => {
     })
   }
 
-  const year = options.pinnedYear
-    ? options.pinnedYear
-    : removeFalsy([options.startYear, options.endYear]).join('-')
-  const license = (options.license || user.license || 'MIT').toUpperCase()
-  const format = options.format || user.format || 'html'
-
   try {
-    const content = await renderFile(path.join(__dirname, '..', 'licenses', `${license}.ejs`), {
+    const content = await renderFile(path.join(directoryName, '..', 'licenses', `${license}.ejs`), {
       info: `${year} ${name}`,
       theme: user.theme || 'default',
       gravatar
     })
 
     if (format === 'txt') {
-      const { articleContent } = content.match(/<article>(?<articleContent>.*)<\/article>/ms).groups
+      const {articleContent} = content.match(/<article>(?<articleContent>.*)<\/article>/ms).groups
 
       response
         .set('Content-Type', 'text/plain; charset=UTF-8')
@@ -111,8 +126,11 @@ module.exports = async (_, response) => {
       response.send(content)
       return
     }
-    response.json({ ...user, ...options })
+
+    response.json({...user, ...options})
   } catch (error) {
     response.status(500).send(error)
   }
 }
+
+export default getRoute
diff --git a/routes/post.js b/routes/post.js
index e49a32fb..eff6031d 100644
--- a/routes/post.js
+++ b/routes/post.js
@@ -1,22 +1,29 @@
-const path = require('path')
-const btoa = require('btoa')
-const { version } = require(path.join(__dirname, '..', 'package.json'))
-const size = require('any-size')
-const { Octokit } = require('@octokit/rest')
-const pathExists = require('path-exists')
-const writeJsonFile = require('write-json-file')
+import path, {dirname} from 'node:path'
+import toBase64 from 'btoa'
+import {readPackageAsync as readPackage} from 'read-pkg'
+import size from 'any-size'
+import {Octokit} from '@octokit/rest'
+import pathExists from 'path-exists'
+import writeJsonFile from 'write-json-file'
+import yn from 'yn'
+import is from '@sindresorhus/is'
+
+import {fileURLToPath} from 'node:url'
+
+import {isDomainId} from './utils.js'
+
+const directoryName = dirname(fileURLToPath(import.meta.url))
+
+const {version} = await readPackage()
+
 const github = new Octokit({
   // GitHub personal access token
   auth: process.env.github_token,
   // User agent with version from package.json
   userAgent: `mit-license v${version}`
 })
-const yn = require('yn')
-const is = require('@sindresorhus/is')
 
-const { isDomainId } = require('./utils')
-
-function getUserData ({ query, body }) {
+function getUserData({query, body}) {
   // If query parameters provided
   if (size(query) > 0) {
     return query
@@ -31,24 +38,23 @@ function getUserData ({ query, body }) {
   return body
 }
 
-// HTTP POST API
-module.exports = async (request, response) => {
-  const { hostname } = request
+const postRoute = async (request, response) => {
+  const {hostname} = request
 
   // Get different parts of hostname (example: remy.mit-license.org -> ['remy', 'mit-license', 'org'])
-  const params = hostname.split('.')
+  const parameters = hostname.split('.')
 
   // This includes the copyright, year, etc.
   const userData = getUserData(request)
 
   // If there isn't enough part of the hostname
-  if (params.length < 2) {
+  if (parameters.length < 2) {
     response.status(400).send('Please specify a subdomain in the URL.')
     return
   }
 
   // Extract the name from the URL
-  const [id] = params
+  const [id] = parameters
 
   if (!isDomainId(id)) {
     // Return a vague error intentionally
@@ -62,7 +68,7 @@ module.exports = async (request, response) => {
   }
 
   // Check if the user file exists in the users directory
-  if (await pathExists(path.join(__dirname, '..', 'users', `${id}.json`))) {
+  if (await pathExists(path.join(directoryName, '..', 'users', `${id}.json`))) {
     response
       .status(409)
       .send(
@@ -73,7 +79,7 @@ module.exports = async (request, response) => {
 
   if (userData.gravatar) {
     // Parse the string version of a boolean or similar
-    userData.gravatar = yn(userData.gravatar, { lenient: true })
+    userData.gravatar = yn(userData.gravatar, {lenient: true})
     if (is.undefined(userData.gravatar)) {
       response
         .status(400)
@@ -98,13 +104,13 @@ module.exports = async (request, response) => {
         repo: 'mit-license',
         path: `users/${id}.json`,
         message: `Automated creation of user ${id}.`,
-        content: btoa(JSON.stringify(userData, 0, 2)),
+        content: toBase64(JSON.stringify(userData, 0, 2)),
         committer: {
           name: 'MIT License Bot',
           email: 'remy@leftlogic.com'
         }
       }),
-      writeJsonFile(path.join(__dirname, '..', 'users', `${id}.json`), userData, { indent: undefined })
+      writeJsonFile(path.join(directoryName, '..', 'users', `${id}.json`), userData, {indent: undefined})
     ])
 
     response.status(201).send(`MIT license page created: https://${hostname}`)
@@ -116,3 +122,6 @@ module.exports = async (request, response) => {
       )
   }
 }
+
+// HTTP POST API
+export default postRoute
diff --git a/routes/utils.js b/routes/utils.js
index 763b46a2..78317984 100644
--- a/routes/utils.js
+++ b/routes/utils.js
@@ -1 +1 @@
-exports.isDomainId = value => /^[\w-_]+$/.test(value)
+export const isDomainId = value => /^[\w-_]+$/.test(value)
diff --git a/server.js b/server.js
index 2ed970fd..04bf9066 100644
--- a/server.js
+++ b/server.js
@@ -5,16 +5,25 @@ IMPORTANT:   Set the `github_token` environment variable to a personal access to
 Server port: The `PORT` environment variable can also be set to control the port the server
              should be hosted on.
 */
-const express = require('express')
-const minify = require('express-minify')
-const favicon = require('serve-favicon')
-const postcssMiddleware = require('postcss-middleware')
-const tempDirectory = require('temp-dir')
-const path = require('path')
+import path, {dirname} from 'node:path'
+import express from 'express'
+import minify from 'express-minify'
+import favicon from 'serve-favicon'
+import postcssMiddleware from 'postcss-middleware'
+import tempDirectory from 'temp-dir'
+import postcssPresetEnv from 'postcss-preset-env'
+import cors from 'cors'
+
+import {fileURLToPath} from 'node:url'
+
+import postRoute from './routes/post.js'
+import getRoute from './routes/get.js'
 
 // Server
 const PORT = process.env.PORT || 8080
 
+const directoryName = dirname(fileURLToPath(import.meta.url))
+
 // Prepare application
 const app = express()
 app.use(
@@ -22,22 +31,22 @@ app.use(
     cache: tempDirectory
   })
 )
-app.use(favicon(path.join(__dirname, 'favicon.ico')))
-app.set('views', path.join(__dirname, '/licenses'))
+app.use(favicon(path.join(directoryName, 'favicon.ico')))
+app.set('views', path.join(directoryName, '/licenses'))
 
 // Setup static files
 app.use('/robots.txt', express.static('robots.txt'))
-app.use('/favicon.ico', express.static(`${__dirname}/favicon.ico`))
+app.use('/favicon.ico', express.static(`${directoryName}/favicon.ico`))
 app.use(
   '/themes',
   postcssMiddleware({
     plugins: [
-      require('postcss-preset-env')({
+      postcssPresetEnv({
         overrideBrowserslist: '>= 0%'
       })
     ],
-    src (request) {
-      return path.join(__dirname, 'themes', request.path)
+    src(request) {
+      return path.join(directoryName, 'themes', request.path)
     }
   }),
   express.static('themes')
@@ -46,7 +55,7 @@ app.use(
 // Middleware
 
 // CORS
-app.use(require('cors')())
+app.use(cors())
 // Parse URL-encoded bodies (as sent by HTML forms)
 app.use(
   express.urlencoded({
@@ -56,13 +65,9 @@ app.use(
 // Parse JSON bodies (as sent by API clients)
 app.use(express.json())
 
-// Capture the id from the subdomain and options from parts of the url
-app.use(require('./middleware/load-user'))
-app.use(require('./middleware/load-options'))
-
 // HTTP endpoints
-app.post('/', require('./routes/post'))
-app.get('/*', require('./routes/get'))
+app.post('/', postRoute)
+app.get('/*', getRoute)
 
 // Start listening for HTTP requests
 app.listen(PORT, () => {
diff --git a/test.js b/test.js
index 9b4315b1..7320a4aa 100644
--- a/test.js
+++ b/test.js
@@ -1,78 +1,79 @@
-const { promises: fs } = require('fs')
-const writeJsonFile = require('write-json-file')
-const CSS = require('css')
-const { isDomainId } = require('./routes/utils')
-const hasFlag = require('has-flag')
-const getExtension = require('file-ext')
-const path = require('path-extra')
-const is = require('@sindresorhus/is')
+import {promises as fs} from 'node:fs'
+import writeJsonFile from 'write-json-file'
+import {parse as parseCSS} from 'css'
+import hasFlag from 'has-flag'
+import getExtension from 'file-ext'
+import path from 'path-extra'
+import is from '@sindresorhus/is'
+import {isDomainId} from './routes/utils.js'
 
-async function report (content, fix) {
+async function report(content, fix) {
   console.error(content)
-  if (fix && hasFlag('--fix')) await fix()
+  if (fix && hasFlag('--fix')) {
+    await fix()
+  }
+
   process.exitCode = 1
 }
 
-(async () => {
-  const users = await fs.readdir('users')
+const users = await fs.readdir('users')
 
-  for (const user of users) {
-    if (getExtension(user) !== 'json') {
-      await report(`${user} is not a json file`, async () => {
-        await fs.unlink(user)
-      })
-    }
+for await (const user of users) {
+  if (getExtension(user) !== 'json') {
+    await report(`${user} is not a json file`, async () => {
+      await fs.unlink(user)
+    })
+  }
 
-    if (!isDomainId(path.base(user))) {
-      await report(`${user} is not a valid domain id.`)
-    }
+  if (!isDomainId(path.base(user))) {
+    await report(`${user} is not a valid domain id.`)
+  }
+
+  try {
+    const data = await fs.readFile(path.join('users', user), 'utf8')
 
     try {
-      const data = await fs.readFile(path.join('users', user), 'utf8')
+      const parsedData = JSON.parse(data)
 
-      try {
-        const parsedData = JSON.parse(data)
-
-        if (!parsedData.locked && !parsedData.copyright) {
-          report(`Copyright not specified in ${user}`)
-        }
-
-        if (parsedData.version) {
-          await report(`Version tag found in ${user}`, async () => {
-            delete parsedData.version
-            await writeJsonFile(path.join('users', user), parsedData, { indent: 2 })
-          })
-        }
-
-        if (is.string(parsedData.gravatar)) {
-          await report(`Gravatar boolean encoded as string found in ${user}`, async () => {
-            parsedData.gravatar = parsedData.gravatar === 'true'
-            const stringified = `${JSON.stringify(parsedData, 0, 2)}\n`
-            await fs.writeFile(path.join('users', user), stringified)
-          })
-        }
-      } catch ({ message }) {
-        report(`Invalid JSON in ${user} (${message})`)
+      if (!parsedData.locked && !parsedData.copyright) {
+        report(`Copyright not specified in ${user}`)
       }
-    } catch ({ message }) {
-      report(`Unable to read ${user} (${message})`)
+
+      if (parsedData.version) {
+        await report(`Version tag found in ${user}`, async () => {
+          delete parsedData.version
+          await writeJsonFile(path.join('users', user), parsedData, {indent: 2})
+        })
+      }
+
+      if (is.string(parsedData.gravatar)) {
+        await report(`Gravatar boolean encoded as string found in ${user}`, async () => {
+          parsedData.gravatar = parsedData.gravatar === 'true'
+          const stringified = `${JSON.stringify(parsedData, 0, 2)}\n`
+          await fs.writeFile(path.join('users', user), stringified)
+        })
+      }
+    } catch ({message}) {
+      report(`Invalid JSON in ${user} (${message})`)
+    }
+  } catch ({message}) {
+    report(`Unable to read ${user} (${message})`)
+  }
+}
+
+const themes = await fs.readdir('themes')
+
+for await (const theme of themes) {
+  if (getExtension(theme) === 'css') {
+    try {
+      const cssData = await fs.readFile(path.join('themes', theme), 'utf8')
+      try {
+        parseCSS(cssData)
+      } catch ({message}) {
+        report(`Invalid CSS in ${theme} (${message})`)
+      }
+    } catch ({message}) {
+      report(`Unable to read ${theme} (${message})`)
     }
   }
-
-  const themes = await fs.readdir('themes')
-
-  for (const theme of themes) {
-    if (getExtension(theme) === 'css') {
-      try {
-        const cssData = await fs.readFile(path.join('themes', theme), 'utf8')
-        try {
-          CSS.parse(cssData)
-        } catch ({ message }) {
-          report(`Invalid CSS in ${theme} (${message})`)
-        }
-      } catch ({ message }) {
-        report(`Unable to read ${theme} (${message})`)
-      }
-    }
-  }
-})()
+}
diff --git a/yarn.lock b/yarn.lock
index c7a651d7..e2706fae 100644
Binary files a/yarn.lock and b/yarn.lock differ