diff --git a/.eslintrc b/.eslintrc
new file mode 100644
index 0000000..de8c630
--- /dev/null
+++ b/.eslintrc
@@ -0,0 +1,18 @@
+{
+	"root": true,
+
+	"extends": "@ljharb",
+
+	"rules": {
+		"id-length": 0,
+		"new-cap": [2, {
+			"capIsNewExceptions": [
+				"CodePointAt",
+				"RequireObjectCoercible",
+				"SymbolDescriptiveString",
+				"ToString",
+				"UTF16EncodeCodePoint",
+			],
+		}],
+	},
+}
diff --git a/.github/workflows/node-aught.yml b/.github/workflows/node-aught.yml
new file mode 100644
index 0000000..f3cddd8
--- /dev/null
+++ b/.github/workflows/node-aught.yml
@@ -0,0 +1,18 @@
+name: 'Tests: node.js < 10'
+
+on: [pull_request, push]
+
+jobs:
+  tests:
+    uses: ljharb/actions/.github/workflows/node.yml@main
+    with:
+      range: '< 10'
+      type: minors
+      command: npm run tests-only
+
+  node:
+    name: 'node < 10'
+    needs: [tests]
+    runs-on: ubuntu-latest
+    steps:
+      - run: 'echo tests completed'
diff --git a/.github/workflows/node-esm.yml b/.github/workflows/node-esm.yml
new file mode 100644
index 0000000..6d387f2
--- /dev/null
+++ b/.github/workflows/node-esm.yml
@@ -0,0 +1,9 @@
+name: 'Tests: node.js (ESM)'
+
+on: [pull_request, push]
+
+jobs:
+  tests:
+    uses: ljharb/actions/.github/workflows/node-esm.yml@main
+    with:
+      command: npm run tests-esm
\ No newline at end of file
diff --git a/.github/workflows/node-pretest.yml b/.github/workflows/node-pretest.yml
new file mode 100644
index 0000000..765edf7
--- /dev/null
+++ b/.github/workflows/node-pretest.yml
@@ -0,0 +1,7 @@
+name: 'Tests: pretest/posttest'
+
+on: [pull_request, push]
+
+jobs:
+  tests:
+    uses: ljharb/actions/.github/workflows/pretest.yml@main
diff --git a/.github/workflows/node-tens.yml b/.github/workflows/node-tens.yml
new file mode 100644
index 0000000..b49ceb1
--- /dev/null
+++ b/.github/workflows/node-tens.yml
@@ -0,0 +1,18 @@
+name: 'Tests: node.js >= 10'
+
+on: [pull_request, push]
+
+jobs:
+  tests:
+    uses: ljharb/actions/.github/workflows/node.yml@main
+    with:
+      range: '>= 10'
+      type: minors
+      command: npm run tests-only
+
+  node:
+    name: 'node >= 10'
+    needs: [tests]
+    runs-on: ubuntu-latest
+    steps:
+      - run: 'echo tests completed'
diff --git a/.github/workflows/rebase.yml b/.github/workflows/rebase.yml
new file mode 100644
index 0000000..5b6d04b
--- /dev/null
+++ b/.github/workflows/rebase.yml
@@ -0,0 +1,15 @@
+name: Automatic Rebase
+
+on: [pull_request_target]
+
+jobs:
+  _:
+    name: "Automatic Rebase"
+
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v2
+      - uses: ljharb/rebase@master
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
diff --git a/.github/workflows/require-allow-edits.yml b/.github/workflows/require-allow-edits.yml
new file mode 100644
index 0000000..7b842f8
--- /dev/null
+++ b/.github/workflows/require-allow-edits.yml
@@ -0,0 +1,12 @@
+name: Require “Allow Edits”
+
+on: [pull_request_target]
+
+jobs:
+  _:
+    name: "Require “Allow Edits”"
+
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: ljharb/require-allow-edits@main
diff --git a/.gitignore b/.gitignore
index 52ab08e..335819f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -107,3 +107,5 @@ dist
 npm-shrinkwrap.json
 package-lock.json
 yarn.lock
+
+.npmignore
diff --git a/.npmrc b/.npmrc
index 43c97e7..eacea13 100644
--- a/.npmrc
+++ b/.npmrc
@@ -1 +1,3 @@
 package-lock=false
+allow-same-version=true
+message=v%s
diff --git a/.nycrc b/.nycrc
new file mode 100644
index 0000000..bdd626c
--- /dev/null
+++ b/.nycrc
@@ -0,0 +1,9 @@
+{
+	"all": true,
+	"check-coverage": false,
+	"reporter": ["text-summary", "text", "html", "json"],
+	"exclude": [
+		"coverage",
+		"test"
+	]
+}
diff --git a/CHANGELOG.md b/CHANGELOG.md
new file mode 100644
index 0000000..03a962f
--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1,6 @@
+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
diff --git a/README.md b/README.md
index 8c3623a..f3a0ab1 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,83 @@
-# String.prototype.toWellFormed
+# string.prototype.towellformed <sup>[![Version Badge][npm-version-svg]][package-url]</sup>
+
+[![github actions][actions-image]][actions-url]
+[![coverage][codecov-image]][codecov-url]
+[![dependency status][deps-svg]][deps-url]
+[![dev dependency status][dev-deps-svg]][dev-deps-url]
+[![License][license-image]][license-url]
+[![Downloads][downloads-image]][downloads-url]
+
+[![npm badge][npm-badge-png]][package-url]
+
 An ESnext spec-compliant `String.prototype.toWellFormed` shim/polyfill/replacement that works as far down as ES3.
+
+This package implements the [es-shim API](https://github.com/es-shims/api) interface. It works in an ES3-supported environment and complies with the proposed [spec](https://tc39.es/proposal-is-usv-string/).
+
+Because `String.prototype.toWellFormed` depends on a receiver (the `this` value), the main export takes the string to operate on as the first argument.
+
+## Getting started
+
+```sh
+npm install --save string.prototype.towellformed
+```
+
+## Usage/Examples
+
+```js
+var toWellFormed = require('string.prototype.towellformed');
+var assert = require('assert');
+
+var leadingPoo = '\uD83D';
+var trailingPoo = '\uDCA9';
+var wholePoo = leadingPoo + trailingPoo;
+
+var replacementChar = '\uFFFD';
+
+assert.equal(toWellFormed(wholePoo), wholePoo);
+assert.equal(toWellFormed(leadingPoo), replacementChar);
+assert.equal(toWellFormed(trailingPoo), replacementChar);
+```
+
+```js
+var toWellFormed = require('string.prototype.towellformed');
+var assert = require('assert');
+/* when String#toWellFormed is not present */
+delete String.prototype.toWellFormed;
+var shimmed = toWellFormed.shim();
+
+assert.equal(shimmed, toWellFormed.getPolyfill());
+assert.deepEqual(wholePoo.toWellFormed(), toWellFormed(wholePoo));
+assert.deepEqual(leadingPoo.toWellFormed(), toWellFormed(leadingPoo));
+assert.deepEqual(trailingPoo.toWellFormed(), toWellFormed(trailingPoo));
+```
+
+```js
+var toWellFormed = require('string.prototype.towellformed');
+var assert = require('assert');
+/* when String#at is present */
+var shimmed = toWellFormed.shim();
+
+assert.equal(shimmed, String.prototype.toWellFormed);
+assert.deepEqual(wholePoo.toWellFormed(), toWellFormed(wholePoo));
+assert.deepEqual(leadingPoo.toWellFormed(), toWellFormed(leadingPoo));
+assert.deepEqual(trailingPoo.toWellFormed(), toWellFormed(trailingPoo));
+```
+
+## Tests
+Simply clone the repo, `npm install`, and run `npm test`
+
+[package-url]: https://npmjs.org/package/string.prototype.towellformed
+[npm-version-svg]: https://versionbadg.es/es-shims/String.prototype.toWellFormed.svg
+[deps-svg]: https://david-dm.org/es-shims/String.prototype.toWellFormed.svg
+[deps-url]: https://david-dm.org/es-shims/String.prototype.toWellFormed
+[dev-deps-svg]: https://david-dm.org/es-shims/String.prototype.toWellFormed/dev-status.svg
+[dev-deps-url]: https://david-dm.org/es-shims/String.prototype.toWellFormed#info=devDependencies
+[npm-badge-png]: https://nodei.co/npm/string.prototype.towellformed.png?downloads=true&stars=true
+[license-image]: https://img.shields.io/npm/l/string.prototype.towellformed.svg
+[license-url]: LICENSE
+[downloads-image]: https://img.shields.io/npm/dm/string.prototype.towellformed.svg
+[downloads-url]: https://npm-stat.com/charts.html?package=string.prototype.towellformed
+[codecov-image]: https://codecov.io/gh/es-shims/String.prototype.toWellFormed/branch/main/graphs/badge.svg
+[codecov-url]: https://app.codecov.io/gh/es-shims/String.prototype.toWellFormed/
+[actions-image]: https://img.shields.io/endpoint?url=https://github-actions-badge-u3jn4tfpocch.runkit.sh/es-shims/String.prototype.toWellFormed
+[actions-url]: https://github.com/es-shims/String.prototype.toWellFormed/actions
diff --git a/auto.js b/auto.js
new file mode 100644
index 0000000..8ebf606
--- /dev/null
+++ b/auto.js
@@ -0,0 +1,3 @@
+'use strict';
+
+require('./shim')();
diff --git a/implementation.js b/implementation.js
new file mode 100644
index 0000000..a08e78d
--- /dev/null
+++ b/implementation.js
@@ -0,0 +1,24 @@
+'use strict';
+
+var CodePointAt = require('es-abstract/2022/CodePointAt');
+// var UTF16EncodeCodePoint = require('es-abstract/2022/UTF16EncodeCodePoint');
+var RequireObjectCoercible = require('es-abstract/2022/RequireObjectCoercible');
+var ToString = require('es-abstract/2022/ToString');
+
+module.exports = function toWellFormed() {
+	var O = RequireObjectCoercible(this); // step 1
+	var S = ToString(O); // step 2
+	var strLen = S.length; // step 3
+	var k = 0; // step 4
+	var result = ''; // step 5
+	while (k < strLen) { // step 6
+		var cp = CodePointAt(S, k); // step 6.a
+		if (cp['[[IsUnpairedSurrogate]]']) { // step 6.b
+			result += '\uFFFD'; // step 6.b.i
+		} else { // step 6.c
+			result += cp['[[CodePoint]]']; // UTF16EncodeCodePoint(cp['[[CodePoint]]']); // step 6.c.i
+		}
+		k += cp['[[CodeUnitCount]]']; // step 6.d
+	}
+	return result; // step 7
+};
diff --git a/index.js b/index.js
new file mode 100644
index 0000000..fff1034
--- /dev/null
+++ b/index.js
@@ -0,0 +1,24 @@
+'use strict';
+
+var define = require('define-properties');
+var RequireObjectCoercible = require('es-abstract/2022/RequireObjectCoercible');
+var callBind = require('call-bind');
+
+var implementation = require('./implementation');
+
+var getPolyfill = require('./polyfill');
+var bound = callBind(getPolyfill());
+
+var shim = require('./shim');
+
+var boundShim = function toWellFormed(string) {
+	RequireObjectCoercible(string);
+	return bound(string);
+};
+define(boundShim, {
+	getPolyfill: getPolyfill,
+	implementation: implementation,
+	shim: shim
+});
+
+module.exports = boundShim;
diff --git a/index.mjs b/index.mjs
new file mode 100644
index 0000000..917f04e
--- /dev/null
+++ b/index.mjs
@@ -0,0 +1,15 @@
+import callBind from 'call-bind';
+import RequireObjectCoercible from 'es-abstract/2022/RequireObjectCoercible.js';
+
+import getPolyfill from 'string.prototype.towellformed/polyfill';
+
+const bound = callBind(getPolyfill());
+
+export default function toWellFormed(string) {
+	RequireObjectCoercible(string);
+	return bound(string);
+}
+
+export { default as getPolyfill } from 'string.prototype.towellformed/polyfill';
+export { default as implementation } from 'string.prototype.towellformed/implementation';
+export { default as shim } from 'string.prototype.towellformed/shim';
diff --git a/package.json b/package.json
new file mode 100644
index 0000000..00e11b5
--- /dev/null
+++ b/package.json
@@ -0,0 +1,96 @@
+{
+	"name": "string.prototype.towellformed",
+	"version": "0.0.0",
+	"description": "An ESnext spec-compliant `String.prototype.toWellFormed` shim/polyfill/replacement that works as far down as ES3.",
+	"main": "index.js",
+	"exports": {
+		".": [
+			{
+				"import": "./index.mjs",
+				"require": "./index.js",
+				"default": "./index.js"
+			},
+			"./index.js"
+		],
+		"./auto": "./auto.js",
+		"./polyfill": "./polyfill.js",
+		"./implementation": "./implementation.js",
+		"./shim": "./shim.js",
+		"./package.json": "./package.json"
+	},
+	"directories": {
+		"test": "test"
+	},
+	"scripts": {
+		"prepack": "npmignore --auto --commentLines=autogenerated",
+		"prepublish": "not-in-publish || npm run prepublishOnly",
+		"prepublishOnly": "safe-publish-latest",
+		"pretest": "npm run lint",
+		"lint": "eslint --ext=js,mjs .",
+		"postlint": "es-shim-api --bound",
+		"tests-only": "nyc tape 'test/**/*.js'",
+		"tests-esm": "nyc node test/index.mjs",
+		"test": "npm run tests-only && npm run tests-esm",
+		"posttest": "aud --production",
+		"version": "auto-changelog && git add CHANGELOG.md",
+		"postversion": "auto-changelog && git add CHANGELOG.md && git commit --no-edit --amend && git tag -f \"v$(node -e \"console.log(require('./package.json').version)\")\""
+	},
+	"repository": {
+		"type": "git",
+		"url": "git+https://github.com/es-shims/String.prototype.toWellFormed.git"
+	},
+	"keywords": [
+		"javascript",
+		"ecmascript",
+		"polyfill",
+		"shim",
+		"es-shim API",
+		"unicode",
+		"string",
+		"surrogate",
+		"pair",
+		"well-formed",
+		"String.prototype.toWellFormed"
+	],
+	"author": "Jordan Harband <ljharb@gmail.com>",
+	"funding": {
+		"url": "https://github.com/sponsors/ljharb"
+	},
+	"license": "MIT",
+	"bugs": {
+		"url": "https://github.com/es-shims/String.prototype.toWellFormed/issues"
+	},
+	"homepage": "https://github.com/es-shims/String.prototype.toWellFormed#readme",
+	"devDependencies": {
+		"@es-shims/api": "^2.2.3",
+		"@ljharb/eslint-config": "^21.0.0",
+		"aud": "^2.0.0",
+		"auto-changelog": "^2.4.0",
+		"es-value-fixtures": "^1.4.2",
+		"eslint": "=8.8.0",
+		"functions-have-names": "^1.2.3",
+		"has-strict-mode": "^1.0.1",
+		"npmignore": "^0.3.0",
+		"nyc": "^10.3.2",
+		"safe-publish-latest": "^2.0.0",
+		"tape": "^5.6.0"
+	},
+	"dependencies": {
+		"call-bind": "^1.0.2",
+		"define-properties": "^1.1.4",
+		"es-abstract": "^1.20.2"
+	},
+	"auto-changelog": {
+		"output": "CHANGELOG.md",
+		"template": "keepachangelog",
+		"unreleased": false,
+		"commitLimit": false,
+		"backfillLimit": false,
+		"hideCredit": true
+	},
+	"publishConfig": {
+		"ignore": [
+			".github/workflows"
+		]
+	}
+}
diff --git a/polyfill.js b/polyfill.js
new file mode 100644
index 0000000..2de8dc9
--- /dev/null
+++ b/polyfill.js
@@ -0,0 +1,7 @@
+'use strict';
+
+var implementation = require('./implementation');
+
+module.exports = function getPolyfill() {
+	return String.prototype.toWellFormed || implementation;
+};
diff --git a/shim.js b/shim.js
new file mode 100644
index 0000000..b4598e7
--- /dev/null
+++ b/shim.js
@@ -0,0 +1,14 @@
+'use strict';
+
+var define = require('define-properties');
+var getPolyfill = require('./polyfill');
+
+module.exports = function shimStringPrototypeToWellFormed() {
+	var polyfill = getPolyfill();
+	define(
+		String.prototype,
+		{ toWellFormed: polyfill },
+		{ toWellFormed: function () { return String.prototype.toWellFormed !== polyfill; } }
+	);
+	return polyfill;
+};
diff --git a/test/implementation.js b/test/implementation.js
new file mode 100644
index 0000000..4dd2a4a
--- /dev/null
+++ b/test/implementation.js
@@ -0,0 +1,20 @@
+'use strict';
+
+var implementation = require('../implementation');
+var callBind = require('call-bind');
+var test = require('tape');
+var hasStrictMode = require('has-strict-mode')();
+var runTests = require('./tests');
+
+test('as a function', function (t) {
+	t.test('bad first arg/receiver', { skip: !hasStrictMode }, function (st) {
+		/* eslint no-useless-call: 0 */
+		st['throws'](function () { implementation.call(undefined); }, TypeError, 'undefined is not an object');
+		st['throws'](function () { implementation.call(null); }, TypeError, 'null is not an object');
+		st.end();
+	});
+
+	runTests(callBind(implementation), t);
+
+	t.end();
+});
diff --git a/test/index.js b/test/index.js
new file mode 100644
index 0000000..c4f13d5
--- /dev/null
+++ b/test/index.js
@@ -0,0 +1,17 @@
+'use strict';
+
+var bound = require('../');
+var test = require('tape');
+var runTests = require('./tests');
+
+test('as a function', function (t) {
+	t.test('bad receiver', function (st) {
+		st['throws'](bound.bind(null, undefined), TypeError, 'undefined is not an object');
+		st['throws'](bound.bind(null, null), TypeError, 'null is not an object');
+		st.end();
+	});
+
+	runTests(bound, t);
+
+	t.end();
+});
diff --git a/test/index.mjs b/test/index.mjs
new file mode 100644
index 0000000..478a190
--- /dev/null
+++ b/test/index.mjs
@@ -0,0 +1,31 @@
+import bound from 'string.prototype.towellformed';
+import * as Module from 'string.prototype.towellformed';
+import test from 'tape';
+import runTests from './tests.js';
+
+test('as a function', (t) => {
+	t.test('bad receiver', (st) => {
+		st.throws(() => bound(undefined), TypeError, 'undefined is not an object');
+		st.throws(() => bound(null), TypeError, 'null is not an object');
+		st.end();
+	});
+
+	runTests(bound, t);
+
+	t.end();
+});
+
+test('named exports', async (t) => {
+	t.deepEqual(
+		Object.keys(Module).sort(),
+		['default', 'shim', 'getPolyfill', 'implementation'].sort(),
+		'has expected named exports',
+	);
+
+	const { shim, getPolyfill, implementation } = Module;
+	t.equal((await import('string.prototype.towellformed/shim')).default, shim, 'shim named export matches deep export');
+	t.equal((await import('string.prototype.towellformed/implementation')).default, implementation, 'implementation named export matches deep export');
+	t.equal((await import('string.prototype.towellformed/polyfill')).default, getPolyfill, 'getPolyfill named export matches deep export');
+
+	t.end();
+});
diff --git a/test/shimmed.js b/test/shimmed.js
new file mode 100644
index 0000000..bfa8b52
--- /dev/null
+++ b/test/shimmed.js
@@ -0,0 +1,35 @@
+'use strict';
+
+require('../auto');
+
+var test = require('tape');
+var defineProperties = require('define-properties');
+var callBind = require('call-bind');
+var isEnumerable = Object.prototype.propertyIsEnumerable;
+var functionsHaveNames = require('functions-have-names')();
+var hasStrictMode = require('has-strict-mode')();
+
+var runTests = require('./tests');
+
+test('shimmed', function (t) {
+	t.equal(String.prototype.toWellFormed.length, 0, 'String#toWellFormed has a length of 0');
+	t.test('Function name', { skip: !functionsHaveNames }, function (st) {
+		st.equal(String.prototype.toWellFormed.name, 'toWellFormed', 'String#toWellFormed has name "toWellFormed"');
+		st.end();
+	});
+
+	t.test('enumerability', { skip: !defineProperties.supportsDescriptors }, function (et) {
+		et.equal(false, isEnumerable.call(String.prototype, 'toWellFormed'), 'String#toWellFormed is not enumerable');
+		et.end();
+	});
+
+	t.test('bad receiver', { skip: !hasStrictMode }, function (st) {
+		st['throws'](function () { return String.prototype.toWellFormed.call(undefined); }, TypeError, 'undefined is not an object');
+		st['throws'](function () { return String.prototype.toWellFormed.call(null); }, TypeError, 'null is not an object');
+		st.end();
+	});
+
+	runTests(callBind(String.prototype.toWellFormed), t);
+
+	t.end();
+});
diff --git a/test/tests.js b/test/tests.js
new file mode 100644
index 0000000..632fc44
--- /dev/null
+++ b/test/tests.js
@@ -0,0 +1,45 @@
+'use strict';
+
+var v = require('es-value-fixtures');
+var forEach = require('for-each');
+var inspect = require('object-inspect');
+
+var SymbolDescriptiveString = require('es-abstract/2022/SymbolDescriptiveString');
+
+var leadingPoo = '\uD83D';
+var trailingPoo = '\uDCA9';
+var wholePoo = leadingPoo + trailingPoo;
+
+var replacementChar = '\uFFFD';
+
+module.exports = function (toWellFormed, t) {
+	t.test('well-formed strings', function (st) {
+		forEach(v.nonStrings.concat(v.strings, wholePoo), function (value) {
+			if (value != null) { // eslint-disable-line eqeqeq
+				var string = typeof value === 'symbol' ? SymbolDescriptiveString(value) : String(value);
+				st.equal(
+					toWellFormed(string),
+					string,
+					inspect(string) + ' (from ' + inspect(value) + ') is well-formed'
+				);
+			}
+		});
+
+		st.end();
+	});
+
+	t.test('not well-formed strings', function (st) {
+		st.equal(
+			toWellFormed(leadingPoo),
+			replacementChar,
+			'a string with a leading surrogate but no trailing surrogate has the lone surrogate replaced as expected'
+		);
+		st.equal(
+			toWellFormed(trailingPoo),
+			replacementChar,
+			'a string with a trailing surrogate but no leading surrogate has the lone surrogate replaced as expected'
+		);
+
+		st.end();
+	});
+};