diff --git a/lib/url-state-machine.js b/lib/url-state-machine.js
index 990339214..d7eec7ca1 100644
--- a/lib/url-state-machine.js
+++ b/lib/url-state-machine.js
@@ -486,7 +486,7 @@ function URLStateMachine(input, base, encodingOverride, url, stateOverride) {
   this.stateOverride = stateOverride;
   this.url = url;
   this.failure = false;
-  this.parseError = false;
+  this.validationErrors = [];
 
   if (!this.url) {
     this.url = {
@@ -502,14 +502,14 @@ function URLStateMachine(input, base, encodingOverride, url, stateOverride) {
 
     const res = trimControlChars(this.input);
     if (res !== this.input) {
-      this.parseError = true;
+      this.validationErrors.push("invalid-URL-unit");
     }
     this.input = res;
   }
 
   const res = trimTabAndNewline(this.input);
   if (res !== this.input) {
-    this.parseError = true;
+    this.validationErrors.push("invalid-URL-unit");
   }
   this.input = res;
 
@@ -545,7 +545,6 @@ URLStateMachine.prototype["parse scheme start"] = function parseSchemeStart(c, c
     this.state = "no scheme";
     --this.pointer;
   } else {
-    this.parseError = true;
     return failure;
   }
 
@@ -583,7 +582,7 @@ URLStateMachine.prototype["parse scheme"] = function parseScheme(c, cStr) {
     this.buffer = "";
     if (this.url.scheme === "file") {
       if (this.input[this.pointer + 1] !== p("/") || this.input[this.pointer + 2] !== p("/")) {
-        this.parseError = true;
+        this.validationErrors.push("special-scheme-missing-following-solidus");
       }
       this.state = "file";
     } else if (isSpecial(this.url) && this.base !== null && this.base.scheme === this.url.scheme) {
@@ -602,7 +601,6 @@ URLStateMachine.prototype["parse scheme"] = function parseScheme(c, cStr) {
     this.state = "no scheme";
     this.pointer = -1;
   } else {
-    this.parseError = true;
     return failure;
   }
 
@@ -611,6 +609,7 @@ URLStateMachine.prototype["parse scheme"] = function parseScheme(c, cStr) {
 
 URLStateMachine.prototype["parse no scheme"] = function parseNoScheme(c) {
   if (this.base === null || (hasAnOpaquePath(this.base) && c !== p("#"))) {
+    this.validationErrors.push("missing-scheme-non-relative-URL");
     return failure;
   } else if (hasAnOpaquePath(this.base) && c === p("#")) {
     this.url.scheme = this.base.scheme;
@@ -634,7 +633,7 @@ URLStateMachine.prototype["parse special relative or authority"] = function pars
     this.state = "special authority ignore slashes";
     ++this.pointer;
   } else {
-    this.parseError = true;
+    this.validationErrors.push("special-scheme-missing-following-solidus");
     this.state = "relative";
     --this.pointer;
   }
@@ -658,7 +657,7 @@ URLStateMachine.prototype["parse relative"] = function parseRelative(c) {
   if (c === p("/")) {
     this.state = "relative slash";
   } else if (isSpecial(this.url) && c === p("\\")) {
-    this.parseError = true;
+    this.validationErrors.push("invalid-reverse-solidus");
     this.state = "relative slash";
   } else {
     this.url.username = this.base.username;
@@ -687,7 +686,7 @@ URLStateMachine.prototype["parse relative"] = function parseRelative(c) {
 URLStateMachine.prototype["parse relative slash"] = function parseRelativeSlash(c) {
   if (isSpecial(this.url) && (c === p("/") || c === p("\\"))) {
     if (c === p("\\")) {
-      this.parseError = true;
+      this.validationErrors.push("invalid-reverse-solidus");
     }
     this.state = "special authority ignore slashes";
   } else if (c === p("/")) {
@@ -709,7 +708,7 @@ URLStateMachine.prototype["parse special authority slashes"] = function parseSpe
     this.state = "special authority ignore slashes";
     ++this.pointer;
   } else {
-    this.parseError = true;
+    this.validationErrors.push("special-scheme-missing-following-solidus");
     this.state = "special authority ignore slashes";
     --this.pointer;
   }
@@ -722,7 +721,7 @@ URLStateMachine.prototype["parse special authority ignore slashes"] = function p
     this.state = "authority";
     --this.pointer;
   } else {
-    this.parseError = true;
+    this.validationErrors.push("special-scheme-missing-following-solidus");
   }
 
   return true;
@@ -730,7 +729,7 @@ URLStateMachine.prototype["parse special authority ignore slashes"] = function p
 
 URLStateMachine.prototype["parse authority"] = function parseAuthority(c, cStr) {
   if (c === p("@")) {
-    this.parseError = true;
+    this.validationErrors.push("invalid-credentials");
     if (this.atFlag) {
       this.buffer = `%40${this.buffer}`;
     }
@@ -756,7 +755,7 @@ URLStateMachine.prototype["parse authority"] = function parseAuthority(c, cStr)
   } else if (isNaN(c) || c === p("/") || c === p("?") || c === p("#") ||
              (isSpecial(this.url) && c === p("\\"))) {
     if (this.atFlag && this.buffer === "") {
-      this.parseError = true;
+      this.validationErrors.push("host-missing");
       return failure;
     }
     this.pointer -= countSymbols(this.buffer) + 1;
@@ -776,7 +775,7 @@ URLStateMachine.prototype["parse host"] = function parseHostName(c, cStr) {
     this.state = "file host";
   } else if (c === p(":") && !this.arrFlag) {
     if (this.buffer === "") {
-      this.parseError = true;
+      this.validationErrors.push("host-missing");
       return failure;
     }
 
@@ -796,11 +795,10 @@ URLStateMachine.prototype["parse host"] = function parseHostName(c, cStr) {
              (isSpecial(this.url) && c === p("\\"))) {
     --this.pointer;
     if (isSpecial(this.url) && this.buffer === "") {
-      this.parseError = true;
+      this.validationErrors.push("host-missing");
       return failure;
     } else if (this.stateOverride && this.buffer === "" &&
                (includesCredentials(this.url) || this.url.port !== null)) {
-      this.parseError = true;
       return false;
     }
 
@@ -836,7 +834,7 @@ URLStateMachine.prototype["parse port"] = function parsePort(c, cStr) {
     if (this.buffer !== "") {
       const port = parseInt(this.buffer);
       if (port > 2 ** 16 - 1) {
-        this.parseError = true;
+        this.validationErrors.push("port-out-of-range");
         return failure;
       }
       this.url.port = port === defaultPort(this.url.scheme) ? null : port;
@@ -848,7 +846,7 @@ URLStateMachine.prototype["parse port"] = function parsePort(c, cStr) {
     this.state = "path start";
     --this.pointer;
   } else {
-    this.parseError = true;
+    this.validationErrors.push("port-invalid");
     return failure;
   }
 
@@ -870,7 +868,7 @@ URLStateMachine.prototype["parse file"] = function parseFile(c) {
 
   if (c === p("/") || c === p("\\")) {
     if (c === p("\\")) {
-      this.parseError = true;
+      this.validationErrors.push("invalid-reverse-solidus");
     }
     this.state = "file slash";
   } else if (this.base !== null && this.base.scheme === "file") {
@@ -888,7 +886,7 @@ URLStateMachine.prototype["parse file"] = function parseFile(c) {
       if (!startsWithWindowsDriveLetter(this.input, this.pointer)) {
         shortenPath(this.url);
       } else {
-        this.parseError = true;
+        this.validationErrors.push("file-invalid-Windows-drive-letter");
         this.url.path = [];
       }
 
@@ -906,7 +904,7 @@ URLStateMachine.prototype["parse file"] = function parseFile(c) {
 URLStateMachine.prototype["parse file slash"] = function parseFileSlash(c) {
   if (c === p("/") || c === p("\\")) {
     if (c === p("\\")) {
-      this.parseError = true;
+      this.validationErrors.push("invalid-reverse-solidus");
     }
     this.state = "file host";
   } else {
@@ -928,7 +926,7 @@ URLStateMachine.prototype["parse file host"] = function parseFileHost(c, cStr) {
   if (isNaN(c) || c === p("/") || c === p("\\") || c === p("?") || c === p("#")) {
     --this.pointer;
     if (!this.stateOverride && isWindowsDriveLetterString(this.buffer)) {
-      this.parseError = true;
+      this.validationErrors.push("file-invalid-Windows-drive-letter-host");
       this.state = "path";
     } else if (this.buffer === "") {
       this.url.host = "";
@@ -963,7 +961,7 @@ URLStateMachine.prototype["parse file host"] = function parseFileHost(c, cStr) {
 URLStateMachine.prototype["parse path start"] = function parsePathStart(c) {
   if (isSpecial(this.url)) {
     if (c === p("\\")) {
-      this.parseError = true;
+      this.validationErrors.push("invalid-reverse-solidus");
     }
     this.state = "path";
 
@@ -992,7 +990,7 @@ URLStateMachine.prototype["parse path"] = function parsePath(c) {
   if (isNaN(c) || c === p("/") || (isSpecial(this.url) && c === p("\\")) ||
       (!this.stateOverride && (c === p("?") || c === p("#")))) {
     if (isSpecial(this.url) && c === p("\\")) {
-      this.parseError = true;
+      this.validationErrors.push("invalid-reverse-solidus");
     }
 
     if (isDoubleDot(this.buffer)) {
@@ -1019,12 +1017,12 @@ URLStateMachine.prototype["parse path"] = function parsePath(c) {
       this.state = "fragment";
     }
   } else {
-    // TODO: If c is not a URL code point and not "%", parse error.
+    // TODO: If c is not a URL code point and not "%", invalid-URL-unit validation error.
 
     if (c === p("%") &&
       (!infra.isASCIIHex(this.input[this.pointer + 1]) ||
         !infra.isASCIIHex(this.input[this.pointer + 2]))) {
-      this.parseError = true;
+      this.validationErrors.push("invalid-URL-unit");
     }
 
     this.buffer += utf8PercentEncodeCodePoint(c, isPathPercentEncode);
@@ -1041,15 +1039,13 @@ URLStateMachine.prototype["parse opaque path"] = function parseOpaquePath(c) {
     this.url.fragment = "";
     this.state = "fragment";
   } else {
-    // TODO: Add: not a URL code point
-    if (!isNaN(c) && c !== p("%")) {
-      this.parseError = true;
-    }
+    // TODO: If c is not the EOF code point, not a URL code point, and not U+0025 (%),
+    // invalid-URL-unit validation error.
 
     if (c === p("%") &&
         (!infra.isASCIIHex(this.input[this.pointer + 1]) ||
          !infra.isASCIIHex(this.input[this.pointer + 2]))) {
-      this.parseError = true;
+      this.validationErrors.push("invalid-URL-unit");
     }
 
     if (!isNaN(c)) {
@@ -1076,12 +1072,12 @@ URLStateMachine.prototype["parse query"] = function parseQuery(c, cStr) {
       this.state = "fragment";
     }
   } else if (!isNaN(c)) {
-    // TODO: If c is not a URL code point and not "%", parse error.
+    // TODO: If c is not a URL code point and not "%", invalid-URL-unit validation error.
 
     if (c === p("%") &&
       (!infra.isASCIIHex(this.input[this.pointer + 1]) ||
         !infra.isASCIIHex(this.input[this.pointer + 2]))) {
-      this.parseError = true;
+      this.validationErrors.push("invalid-URL-unit");
     }
 
     this.buffer += cStr;
@@ -1092,11 +1088,11 @@ URLStateMachine.prototype["parse query"] = function parseQuery(c, cStr) {
 
 URLStateMachine.prototype["parse fragment"] = function parseFragment(c) {
   if (!isNaN(c)) {
-    // TODO: If c is not a URL code point and not "%", parse error.
+    // TODO: If c is not a URL code point and not "%", invalid-URL-unit validation error.
     if (c === p("%") &&
       (!infra.isASCIIHex(this.input[this.pointer + 1]) ||
         !infra.isASCIIHex(this.input[this.pointer + 2]))) {
-      this.parseError = true;
+      this.validationErrors.push("invalid-URL-unit");
     }
 
     this.url.fragment += utf8PercentEncodeCodePoint(c, isFragmentPercentEncode);
@@ -1206,17 +1202,17 @@ module.exports.serializeURLOrigin = function (url) {
   }
 };
 
-module.exports.basicURLParse = function (input, options) {
+module.exports.basicURLParseWithErrors = function (input, options) {
   if (options === undefined) {
     options = {};
   }
 
   const usm = new URLStateMachine(input, options.baseURL, options.encodingOverride, options.url, options.stateOverride);
-  if (usm.failure) {
-    return null;
-  }
+  return { url: usm.failure ? null : usm.url, validationErrors: usm.validationErrors };
+};
 
-  return usm.url;
+module.exports.basicURLParse = function (input, options) {
+  return module.exports.basicURLParseWithErrors(input, options).url;
 };
 
 module.exports.setTheUsername = function (url, username) {