diff --git a/benchmarks/core/is-valid-port.mjs b/benchmarks/core/is-valid-port.mjs
new file mode 100644
index 00000000000..0c94bc092bf
--- /dev/null
+++ b/benchmarks/core/is-valid-port.mjs
@@ -0,0 +1,16 @@
+import { bench, group, run } from 'mitata'
+import { isValidPort } from '../../lib/core/util.js'
+
+const string = '1234'
+const number = 1234
+
+group('isValidPort', () => {
+  bench('string', () => {
+    return isValidPort(string)
+  })
+  bench('number', () => {
+    return isValidPort(number)
+  })
+})
+
+await run()
diff --git a/lib/core/util.js b/lib/core/util.js
index b7d7f87a34e..7813f66c438 100644
--- a/lib/core/util.js
+++ b/lib/core/util.js
@@ -52,11 +52,36 @@ function buildURL (url, queryParams) {
   return url
 }
 
+function isValidPort (port) {
+  const value = parseInt(port, 10)
+  return (
+    value === Number(port) &&
+    value >= 0 &&
+    value <= 65535
+  )
+}
+
+function isHttpOrHttpsPrefixed (value) {
+  return (
+    value[0] === 'h' &&
+    value[1] === 't' &&
+    value[2] === 't' &&
+    value[3] === 'p' &&
+    (
+      value[4] === ':' ||
+      (
+        value[4] === 's' &&
+        value[5] === ':'
+      )
+    )
+  )
+}
+
 function parseURL (url) {
   if (typeof url === 'string') {
     url = new URL(url)
 
-    if (!/^https?:/.test(url.origin || url.protocol)) {
+    if (!isHttpOrHttpsPrefixed(url.origin || url.protocol)) {
       throw new InvalidArgumentError('Invalid URL protocol: the URL must start with `http:` or `https:`.')
     }
 
@@ -67,12 +92,12 @@ function parseURL (url) {
     throw new InvalidArgumentError('Invalid URL: The URL argument must be a non-null object.')
   }
 
-  if (!/^https?:/.test(url.origin || url.protocol)) {
+  if (!isHttpOrHttpsPrefixed(url.origin || url.protocol)) {
     throw new InvalidArgumentError('Invalid URL protocol: the URL must start with `http:` or `https:`.')
   }
 
   if (!(url instanceof URL)) {
-    if (url.port != null && url.port !== '' && !Number.isFinite(parseInt(url.port))) {
+    if (url.port != null && url.port !== '' && isValidPort(url.port) === false) {
       throw new InvalidArgumentError('Invalid URL: port must be a valid integer or a string representation of an integer.')
     }
 
@@ -102,11 +127,11 @@ function parseURL (url) {
       ? url.path
       : `${url.pathname || ''}${url.search || ''}`
 
-    if (origin.endsWith('/')) {
-      origin = origin.substring(0, origin.length - 1)
+    if (origin[origin.length - 1] === '/') {
+      origin = origin.slice(0, origin.length - 1)
     }
 
-    if (path && !path.startsWith('/')) {
+    if (path && path[0] !== '/') {
       path = `/${path}`
     }
     // new URL(path, origin) is unsafe when `path` contains an absolute URL
@@ -606,6 +631,8 @@ module.exports = {
   isValidHeaderChar,
   isTokenCharCode,
   parseRangeHeader,
+  isValidPort,
+  isHttpOrHttpsPrefixed,
   nodeMajor,
   nodeMinor,
   nodeHasAutoSelectFamily: nodeMajor > 18 || (nodeMajor === 18 && nodeMinor >= 13),
diff --git a/test/util.js b/test/util.js
index b8b661bca40..6cea23cd4c4 100644
--- a/test/util.js
+++ b/test/util.js
@@ -1,9 +1,10 @@
 'use strict'
 
-const { strictEqual } = require('node:assert')
+const { strictEqual, throws, doesNotThrow } = require('node:assert')
 const { test, describe } = require('node:test')
-const { isBlobLike } = require('../lib/core/util')
+const { isBlobLike, parseURL, isHttpOrHttpsPrefixed, isValidPort } = require('../lib/core/util')
 const { Blob, File } = require('node:buffer')
+const { InvalidArgumentError } = require('../lib/core/errors')
 
 describe('isBlobLike', () => {
   test('buffer', () => {
@@ -65,3 +66,181 @@ describe('isBlobLike', () => {
     strictEqual(isBlobLike(null), false)
   })
 })
+
+describe('isHttpOrHttpsPrefixed', () => {
+  test('returns false for invalid values', () => {
+    strictEqual(isHttpOrHttpsPrefixed('wss:'), false)
+  })
+  test('returns true for "http:" or "https:"', () => {
+    strictEqual(isHttpOrHttpsPrefixed('http:'), true)
+    strictEqual(isHttpOrHttpsPrefixed('https:'), true)
+  })
+})
+
+describe('isValidPort', () => {
+  test('returns false for invalid values', () => {
+    strictEqual(isValidPort(NaN), false)
+    strictEqual(isValidPort(Infinity), false)
+    strictEqual(isValidPort(-Infinity), false)
+    strictEqual(isValidPort(NaN.toString()), false)
+    strictEqual(isValidPort(Infinity.toString()), false)
+    strictEqual(isValidPort(-Infinity.toString()), false)
+    strictEqual(isValidPort('port'), false)
+    strictEqual(isValidPort('65535i'), false)
+  })
+  test('returns true for port in range of 0 to 65535 as number', () => {
+    for (let i = 0; i < 65536; i++) {
+      strictEqual(isValidPort(i), true)
+    }
+  })
+  test('returns true for port in range of 0 to 65535 as string', () => {
+    for (let i = 0; i < 65536; i++) {
+      strictEqual(isValidPort(i.toString()), true)
+    }
+  })
+})
+
+describe('parseURL', () => {
+  test('throws if url is not a string or object', () => {
+    throws(() => { parseURL(null) }, new InvalidArgumentError('Invalid URL: The URL argument must be a non-null object.'))
+    throws(() => { parseURL(1) }, new InvalidArgumentError('Invalid URL: The URL argument must be a non-null object.'))
+    throws(() => { parseURL(true) }, new InvalidArgumentError('Invalid URL: The URL argument must be a non-null object.'))
+    throws(() => { parseURL(false) }, new InvalidArgumentError('Invalid URL: The URL argument must be a non-null object.'))
+    throws(() => { parseURL(false) }, new InvalidArgumentError('Invalid URL: The URL argument must be a non-null object.'))
+  })
+  test('throws if protocol is not beginning with http:', () => {
+    throws(() => { parseURL('ws://www.example.com') }, new InvalidArgumentError('Invalid URL protocol: the URL must start with `http:` or `https:`.'))
+  })
+  test('throws if protocol is not beginning with https:', () => {
+    throws(() => { parseURL('wss://www.example.com') }, new InvalidArgumentError('Invalid URL protocol: the URL must start with `http:` or `https:`.'))
+  })
+  test('returns an URL object if url is a string of an https URL', () => {
+    const url = parseURL('https://www.example.com')
+    strictEqual(url instanceof URL, true)
+    strictEqual(url.href, 'https://www.example.com/')
+  })
+  test('returns an URL object if url is a string of an http URL', () => {
+    const url = parseURL('http://www.example.com')
+    strictEqual(url instanceof URL, true)
+    strictEqual(url.href, 'http://www.example.com/')
+  })
+
+  describe('when url is an instance of URL', () => {
+    test('returns the same URL object', () => {
+      const url = new URL('https://www.example.com')
+      const parsedURL = parseURL(url)
+      strictEqual(parsedURL, url)
+    })
+    test('throws if the URL protocol is not http: or https:', () => {
+      const url = new URL('ws://www.example.com')
+      throws(() => { parseURL(url) }, new InvalidArgumentError('Invalid URL protocol: the URL must start with `http:` or `https:`.'))
+    })
+    test('passes if the URL protocol is http:', () => {
+      const url = new URL('http://www.example.com')
+      delete url.origin
+      doesNotThrow(() => { parseURL(url) })
+    })
+    test('passes if the URL protocol is https:', () => {
+      const url = new URL('https://www.example.com')
+      delete url.origin
+      doesNotThrow(() => { parseURL(url) })
+    })
+    test('passes if the URL protocol is http:', () => {
+      const url = new URL('http://www.example.com')
+      doesNotThrow(() => { parseURL(url) })
+    })
+    test('passes if the URL protocol is https:', () => {
+      const url = new URL('https://www.example.com')
+      doesNotThrow(() => { parseURL(url) })
+    })
+  })
+
+  describe('when url is an common object', () => {
+    test.skip('does not throw if a urlLike object is passed', () => {
+      const url = parseURL({ protocol: 'http:' })
+      console.log(url)
+    })
+
+    describe('port', () => {
+      test('throws if port is not an finite number as string', () => {
+        throws(() => parseURL({ protocol: 'http:', port: 'NaN' }), new InvalidArgumentError('Invalid URL: port must be a valid integer or a string representation of an integer.'))
+      })
+      test('doesn\'t throw if port is valid number', () => {
+        for (let i = 0; i < 65536; i++) {
+          doesNotThrow(() => parseURL({ protocol: 'http:', port: i.toString() }), i.toString())
+        }
+      })
+      test('throws if port is invalid number', () => {
+        throws(() => parseURL({ protocol: 'http:', port: '-1' }), new InvalidArgumentError('Invalid URL: port must be a valid integer or a string representation of an integer.'))
+        throws(() => parseURL({ protocol: 'http:', port: '65536' }), new InvalidArgumentError('Invalid URL: port must be a valid integer or a string representation of an integer.'))
+      })
+      test('sets port based on protocol', () => {
+        strictEqual(parseURL({ protocol: 'http:', hostname: 'www.example.com', path: '/' }).port, '')
+        strictEqual(parseURL({ protocol: 'https:', hostname: 'www.example.com', path: '/' }).port, '')
+      })
+      test('don\'t override port with protocol if port was explicitly set', () => {
+        strictEqual(parseURL({ protocol: 'http:', hostname: 'www.example.com', path: '/', port: 1337 }).port, '1337')
+        strictEqual(parseURL({ protocol: 'https:', hostname: 'www.example.com', path: '/', port: 1337 }).port, '1337')
+      })
+    })
+
+    describe('path', () => {
+      test('doesn\'t throw if path null or undefined', () => {
+        parseURL({ protocol: 'http:', path: null })
+        parseURL({ protocol: 'http:', path: undefined })
+      })
+      test('throws if path is not as string', () => {
+        throws(() => parseURL({ protocol: 'http:', path: 1 }), new InvalidArgumentError('Invalid URL path: the path must be a string or null/undefined.'))
+      })
+      test('doesn\'t throw if path is a string', () => {
+        parseURL({ protocol: 'http:', path: '/' })
+      })
+      test('accepts path with and without leading /', () => {
+        strictEqual(parseURL({ protocol: 'http:', hostname: 'www.example.com', path: 'abc' }).pathname, '/abc')
+        strictEqual(parseURL({ protocol: 'https:', hostname: 'www.example.com', path: '/abc' }).pathname, '/abc')
+      })
+    })
+
+    describe('pathname', () => {
+      test('doesn\'t throw if pathname null or undefined', () => {
+        parseURL({ protocol: 'http:', pathname: null })
+        parseURL({ protocol: 'http:', pathname: undefined })
+      })
+      test('throws if pathname is not as string', () => {
+        throws(() => parseURL({ protocol: 'http:', pathname: 1 }), new InvalidArgumentError('Invalid URL pathname: the pathname must be a string or null/undefined.'))
+      })
+      test('doesn\'t throw if pathname is a string', () => {
+        parseURL({ protocol: 'http:', pathname: '/' })
+      })
+    })
+
+    describe('hostname', () => {
+      test('doesn\'t throw if hostname null or undefined', () => {
+        parseURL({ protocol: 'http:', hostname: null })
+        parseURL({ protocol: 'http:', hostname: undefined })
+      })
+      test('throws if hostname is not as string', () => {
+        throws(() => parseURL({ protocol: 'http:', hostname: 1 }), new InvalidArgumentError('Invalid URL hostname: the hostname must be a string or null/undefined.'))
+      })
+      test('doesn\'t throw if hostname is a string', () => {
+        parseURL({ protocol: 'http:', hostname: 'www.example.com' })
+      })
+    })
+
+    describe('origin', () => {
+      test('doesn\'t throw if origin null or undefined', () => {
+        parseURL({ protocol: 'http:', origin: null })
+        parseURL({ protocol: 'http:', origin: undefined })
+      })
+      test('throws if origin is not as string', () => {
+        throws(() => parseURL({ protocol: 'http:', origin: 1 }), new InvalidArgumentError('Invalid URL protocol: the URL must start with `http:` or `https:`.'))
+      })
+      test('doesn\'t throw if origin is a string', () => {
+        parseURL({ protocol: 'http:', origin: 'https://www.example.com' })
+      })
+      test('removes trailing /', () => {
+        parseURL({ protocol: 'http:', origin: 'https://www.example.com/' })
+      })
+    })
+  })
+})