diff --git a/.config b/.config
index 1a615b4..44ef701 100644
--- a/.config
+++ b/.config
@@ -2,4 +2,3 @@ repo-owner = sanctuary-js
 repo-name = sanctuary-show
 contributing-file = .github/CONTRIBUTING.md
 heading-level = 3
-module-type = commonjs
diff --git a/.eslintrc.json b/.eslintrc.json
index 252ce22..7a81095 100644
--- a/.eslintrc.json
+++ b/.eslintrc.json
@@ -1,6 +1,7 @@
 {
   "root": true,
   "extends": ["./node_modules/sanctuary-style/eslint.json"],
+  "parserOptions": {"sourceType": "module"},
   "overrides": [
     {
       "files": ["*.md"],
diff --git a/.gitignore b/.gitignore
index bd53bbe..cba87a3 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,2 @@
-/.nyc_output/
 /coverage/
 /node_modules/
diff --git a/index.js b/index.js
index 6f37c86..dd5ab37 100644
--- a/index.js
+++ b/index.js
@@ -30,171 +30,152 @@
 //. };
 //. ```
 
-(f => {
+export {show as default};
 
-  'use strict';
+//  $$show :: String
+const $$show = '@@show';
 
-  /* istanbul ignore else */
-  if (typeof module === 'object' && typeof module.exports === 'object') {
-    module.exports = f ();
-  } else if (typeof define === 'function' && define.amd != null) {
-    define ([], f);
-  } else {
-    self.sanctuaryShow = f ();
-  }
+//  seen :: Array Any
+const seen = [];
+
+//  entry :: Object -> String -> String
+const entry = o => k => show (k) + ': ' + show (o[k]);
+
+//  sortedKeys :: Object -> Array String
+const sortedKeys = o => (Object.keys (o)).sort ();
+
+//# show :: Showable a => a -> String
+//.
+//. Returns a useful string representation of the given value.
+//.
+//. Dispatches to the value's `@@show` method if present.
+//.
+//. Where practical, `show (eval ('(' + show (x) + ')')) = show (x)`.
+//.
+//. ```javascript
+//. > show (null)
+//. 'null'
+//.
+//. > show (undefined)
+//. 'undefined'
+//.
+//. > show (true)
+//. 'true'
+//.
+//. > show (new Boolean (false))
+//. 'new Boolean (false)'
+//.
+//. > show (-0)
+//. '-0'
+//.
+//. > show (NaN)
+//. 'NaN'
+//.
+//. > show (new Number (Infinity))
+//. 'new Number (Infinity)'
+//.
+//. > show ('foo\n"bar"\nbaz\n')
+//. '"foo\\n\\"bar\\"\\nbaz\\n"'
+//.
+//. > show (new String (''))
+//. 'new String ("")'
+//.
+//. > show (['foo', 'bar', 'baz'])
+//. '["foo", "bar", "baz"]'
+//.
+//. > show ([[[[[0]]]]])
+//. '[[[[[0]]]]]'
+//.
+//. > show ({x: [1, 2], y: [3, 4], z: [5, 6]})
+//. '{"x": [1, 2], "y": [3, 4], "z": [5, 6]}'
+//. ```
+const show = x => {
+  if (seen.indexOf (x) >= 0) return '<Circular>';
+
+  const repr = Object.prototype.toString.call (x);
+
+  switch (repr) {
+
+    case '[object Null]':
+      return 'null';
+
+    case '[object Undefined]':
+      return 'undefined';
+
+    case '[object Boolean]':
+      return typeof x === 'object' ?
+        'new Boolean (' + show (x.valueOf ()) + ')' :
+        x.toString ();
+
+    case '[object Number]':
+      return typeof x === 'object' ?
+        'new Number (' + show (x.valueOf ()) + ')' :
+        1 / x === -Infinity ? '-0' : x.toString (10);
+
+    case '[object String]':
+      return typeof x === 'object' ?
+        'new String (' + show (x.valueOf ()) + ')' :
+        JSON.stringify (x);
+
+    case '[object RegExp]':
+      return x.toString ();
+
+    case '[object Date]':
+      return 'new Date (' +
+             show (isNaN (x.valueOf ()) ? NaN : x.toISOString ()) +
+             ')';
+
+    case '[object Error]':
+      return 'new ' + x.name + ' (' + show (x.message) + ')';
+
+    case '[object Arguments]':
+      return 'function () { return arguments; } (' +
+             (Array.prototype.map.call (x, show)).join (', ') +
+             ')';
+
+    case '[object Array]':
+      seen.push (x);
+      try {
+        return '[' + ((x.map (show)).concat (
+          sortedKeys (x)
+          .filter (k => !(/^\d+$/.test (k)))
+          .map (entry (x))
+        )).join (', ') + ']';
+      } finally {
+        seen.pop ();
+      }
+
+    case '[object Object]':
+      seen.push (x);
+      try {
+        return (
+          $$show in x &&
+          (x.constructor == null || x.constructor.prototype !== x) ?
+            x[$$show] () :
+            '{' + ((sortedKeys (x)).map (entry (x))).join (', ') + '}'
+        );
+      } finally {
+        seen.pop ();
+      }
+
+    case '[object Set]':
+      seen.push (x);
+      try {
+        return 'new Set (' + show (Array.from (x.values ())) + ')';
+      } finally {
+        seen.pop ();
+      }
+
+    case '[object Map]':
+      seen.push (x);
+      try {
+        return 'new Map (' + show (Array.from (x.entries ())) + ')';
+      } finally {
+        seen.pop ();
+      }
+
+    default:
+      return repr.replace (/^\[(.*)\]$/, '<$1>');
 
-}) (() => {
-
-  'use strict';
-
-  //  $$show :: String
-  const $$show = '@@show';
-
-  //  seen :: Array Any
-  const seen = [];
-
-  //  entry :: Object -> String -> String
-  const entry = o => k => show (k) + ': ' + show (o[k]);
-
-  //  sortedKeys :: Object -> Array String
-  const sortedKeys = o => (Object.keys (o)).sort ();
-
-  //# show :: Showable a => a -> String
-  //.
-  //. Returns a useful string representation of the given value.
-  //.
-  //. Dispatches to the value's `@@show` method if present.
-  //.
-  //. Where practical, `show (eval ('(' + show (x) + ')')) = show (x)`.
-  //.
-  //. ```javascript
-  //. > show (null)
-  //. 'null'
-  //.
-  //. > show (undefined)
-  //. 'undefined'
-  //.
-  //. > show (true)
-  //. 'true'
-  //.
-  //. > show (new Boolean (false))
-  //. 'new Boolean (false)'
-  //.
-  //. > show (-0)
-  //. '-0'
-  //.
-  //. > show (NaN)
-  //. 'NaN'
-  //.
-  //. > show (new Number (Infinity))
-  //. 'new Number (Infinity)'
-  //.
-  //. > show ('foo\n"bar"\nbaz\n')
-  //. '"foo\\n\\"bar\\"\\nbaz\\n"'
-  //.
-  //. > show (new String (''))
-  //. 'new String ("")'
-  //.
-  //. > show (['foo', 'bar', 'baz'])
-  //. '["foo", "bar", "baz"]'
-  //.
-  //. > show ([[[[[0]]]]])
-  //. '[[[[[0]]]]]'
-  //.
-  //. > show ({x: [1, 2], y: [3, 4], z: [5, 6]})
-  //. '{"x": [1, 2], "y": [3, 4], "z": [5, 6]}'
-  //. ```
-  const show = x => {
-    if (seen.indexOf (x) >= 0) return '<Circular>';
-
-    const repr = Object.prototype.toString.call (x);
-
-    switch (repr) {
-
-      case '[object Null]':
-        return 'null';
-
-      case '[object Undefined]':
-        return 'undefined';
-
-      case '[object Boolean]':
-        return typeof x === 'object' ?
-          'new Boolean (' + show (x.valueOf ()) + ')' :
-          x.toString ();
-
-      case '[object Number]':
-        return typeof x === 'object' ?
-          'new Number (' + show (x.valueOf ()) + ')' :
-          1 / x === -Infinity ? '-0' : x.toString (10);
-
-      case '[object String]':
-        return typeof x === 'object' ?
-          'new String (' + show (x.valueOf ()) + ')' :
-          JSON.stringify (x);
-
-      case '[object RegExp]':
-        return x.toString ();
-
-      case '[object Date]':
-        return 'new Date (' +
-               show (isNaN (x.valueOf ()) ? NaN : x.toISOString ()) +
-               ')';
-
-      case '[object Error]':
-        return 'new ' + x.name + ' (' + show (x.message) + ')';
-
-      case '[object Arguments]':
-        return 'function () { return arguments; } (' +
-               (Array.prototype.map.call (x, show)).join (', ') +
-               ')';
-
-      case '[object Array]':
-        seen.push (x);
-        try {
-          return '[' + ((x.map (show)).concat (
-            sortedKeys (x)
-            .filter (k => !(/^\d+$/.test (k)))
-            .map (entry (x))
-          )).join (', ') + ']';
-        } finally {
-          seen.pop ();
-        }
-
-      case '[object Object]':
-        seen.push (x);
-        try {
-          return (
-            $$show in x &&
-            (x.constructor == null || x.constructor.prototype !== x) ?
-              x[$$show] () :
-              '{' + ((sortedKeys (x)).map (entry (x))).join (', ') + '}'
-          );
-        } finally {
-          seen.pop ();
-        }
-
-      case '[object Set]':
-        seen.push (x);
-        try {
-          return 'new Set (' + show (Array.from (x.values ())) + ')';
-        } finally {
-          seen.pop ();
-        }
-
-      case '[object Map]':
-        seen.push (x);
-        try {
-          return 'new Map (' + show (Array.from (x.entries ())) + ')';
-        } finally {
-          seen.pop ();
-        }
-
-      default:
-        return repr.replace (/^\[(.*)\]$/, '<$1>');
-
-    }
-  };
-
-  return show;
-
-});
+  }
+};
diff --git a/package.json b/package.json
index 01f35a6..c94813c 100644
--- a/package.json
+++ b/package.json
@@ -7,6 +7,11 @@
     "type": "git",
     "url": "git://github.com/sanctuary-js/sanctuary-show.git"
   },
+  "type": "module",
+  "exports": {
+    ".": "./index.js",
+    "./package.json": "./package.json"
+  },
   "files": [
     "/LICENSE",
     "/README.md",
@@ -15,6 +20,8 @@
   ],
   "dependencies": {},
   "devDependencies": {
+    "c8": "8.0.x",
+    "oletus": "4.0.x",
     "sanctuary-scripts": "6.0.x"
   },
   "scripts": {
@@ -22,8 +29,5 @@
     "lint": "sanctuary-lint",
     "release": "sanctuary-release",
     "test": "npm run lint && sanctuary-test && npm run doctest"
-  },
-  "mocha": {
-    "ui": "tdd"
   }
 }
diff --git a/scripts/test b/scripts/test
new file mode 100755
index 0000000..5ccef32
--- /dev/null
+++ b/scripts/test
@@ -0,0 +1,10 @@
+#!/usr/bin/env bash
+set -euf -o pipefail
+
+node_modules/.bin/c8 \
+  --check-coverage \
+  --100 \
+  --reporter text \
+  --reporter html \
+  --include index.js \
+  node_modules/.bin/oletus -- test/index.js
diff --git a/test/index.js b/test/index.js
index 97f4b91..235a729 100644
--- a/test/index.js
+++ b/test/index.js
@@ -1,13 +1,10 @@
-'use strict';
+import assert from 'node:assert';
 
-const assert = require ('assert');
+import test from 'oletus';
 
-const show = require ('..');
+import show from 'sanctuary-show';
 
 
-//    NODE_VERSION :: Integer
-const NODE_VERSION = Number (process.version.replace (/^v|[.].*$/g, ''));
-
 //    eq :: a -> b -> Undefined !
 function eq(actual) {
   assert.strictEqual (arguments.length, eq.length);
@@ -86,10 +83,7 @@ test ('arrays', () => {
   eq (show ([])) ('[]');
   eq (show (['foo'])) ('["foo"]');
   eq (show (['foo', 'bar'])) ('["foo", "bar"]');
-  eq (show (/x/.exec ('xyz')))
-     (NODE_VERSION < 10 ?
-      '["x", "index": 0, "input": "xyz"]' :
-      '["x", "groups": undefined, "index": 0, "input": "xyz"]');
+  eq (show (/x/.exec ('xyz'))) ('["x", "groups": undefined, "index": 0, "input": "xyz"]');
   eq (show ((() => { const xs = []; xs.z = true; xs.a = true; return xs; }) ())) ('["a": true, "z": true]');
 });