diff --git a/src/jsc/bindings/NodeURL.cpp b/src/jsc/bindings/NodeURL.cpp
index 59331350446a..8a12f7dc5998 100644
--- a/src/jsc/bindings/NodeURL.cpp
+++ b/src/jsc/bindings/NodeURL.cpp
@@ -112,8 +112,11 @@ bool hasValidPunycodeHost(WTF::StringView host)
 // Mirrors Node's url.domainToASCII/domainToUnicode, which run the input
 // through a WHATWG URL host parse (ada's url.set_hostname on a "ws://x"
 // base). Returns a null String when host parsing fails.
-static String parseDomainAsHost(const String& domain)
+static String parseDomainAsHost(const String& input)
 {
+    // The basic URL parser removes ASCII tab and newline from its input first.
+    String domain = input.removeCharacters([](char16_t c) { return c == '\t' || c == '\n' || c == '\r'; });
+
     // The hostname setter's basic-URL parse stops at the first path, query,
     // fragment, or backslash (special scheme) terminator.
     StringView view { domain };
diff --git a/test/js/node/url/url-domain-ascii-unicode.test.js b/test/js/node/url/url-domain-ascii-unicode.test.js
index 912c93637f79..e8dd276e8aed 100644
--- a/test/js/node/url/url-domain-ascii-unicode.test.js
+++ b/test/js/node/url/url-domain-ascii-unicode.test.js
@@ -96,7 +96,123 @@ describe("url.domainToUnicode", () => {
   }
   for (const [input, expected] of invalids) {
     test(`-> '${input}' is '${expected}'`, () => {
-      expect(url.domainToASCII(input)).toEqual(expected);
+      expect(url.domainToUnicode(input)).toEqual(expected);
     });
   }
 });
+
+// Node implements both functions as a WHATWG host parse of the input (the hostname setter on a "ws://x" URL)
+// and returns "" when that parse fails, so percent-decoding, IPv4/IPv6 canonicalization, tab and newline
+// stripping and the authority terminators all apply. Rows are [input, domainToASCII(input),
+// domainToUnicode(input)]; the expected values are Node's.
+const hostParserParity = [
+  // Valid punycode is kept (lowercased); a label that merely contains "xn--" is not punycode.
+  ["xn--bcher-kva.de", "xn--bcher-kva.de", "b\u00fccher.de"],
+  ["XN--BCHER-KVA.DE", "xn--bcher-kva.de", "b\u00fccher.de"],
+  ["xn--fiqs8s", "xn--fiqs8s", "\u4e2d\u56fd"],
+  ["xn--ls8h.example", "xn--ls8h.example", "\u{1f4a9}.example"],
+  ["xn--6qqa088eba", "xn--6qqa088eba", "\u4f60\u597d\u4f60\u597d"],
+  ["axn--a-ecp.example", "axn--a-ecp.example", "axn--a-ecp.example"],
+  // Forbidden host code points: %, C0 controls, DEL, space.
+  ["a%b", "", ""],
+  ["%", "", ""],
+  ["%ZZ", "", ""],
+  ["a\x01b", "", ""],
+  ["a\x0cb", "", ""],
+  ["a\x7fb", "", ""],
+  ["a b", "", ""],
+  [" a ", "", ""],
+  // Percent-decoding happens before IDNA.
+  ["%41", "a", "a"],
+  ["ex%61mple.com", "example.com", "example.com"],
+  ["%e4%bd%a0%e5%a5%bd", "xn--6qq79v", "\u4f60\u597d"],
+  ["%zz%66%a", "", ""],
+  // ASCII lowercasing.
+  ["EXAMPLE.COM", "example.com", "example.com"],
+  // IPv4 canonicalization and rejection.
+  ["0x7f.1", "127.0.0.1", "127.0.0.1"],
+  ["0x7f.0x0.0x0.0x1", "127.0.0.1", "127.0.0.1"],
+  ["192.168.1.1", "192.168.1.1", "192.168.1.1"],
+  ["999.999.999.999", "", ""],
+  ["1.2.3.4.5", "", ""],
+  ["09.1", "", ""],
+  // IPv6.
+  ["[::1]", "[::1]", "[::1]"],
+  ["[0:0:0:0:0:0:0:1]", "[::1]", "[::1]"],
+  ["[::ffff:127.0.0.1]", "[::ffff:7f00:1]", "[::ffff:7f00:1]"],
+  ["[", "", ""],
+  ["[:", "", ""],
+  ["[::1]:80", "", ""],
+  // Tabs and newlines are removed before anything else: before IDNA runs, so they never end up inside a
+  // punycode label, and before the IPv6 brackets and the port check are looked at.
+  ["ex\tample.com", "example.com", "example.com"],
+  ["a\r\nb", "ab", "ab"],
+  ["b\t\u00fccher.de", "xn--bcher-kva.de", "b\u00fccher.de"],
+  ["\u00df\nxn", "xn--xn-fia", "\u00dfxn"],
+  ["\u03c2a\nxn--bcher-kva", "xn--axn--bcher-kva-phk", "\u03c2axn--bcher-kva"],
+  ["\t[::1]", "[::1]", "[::1]"],
+  ["[::1]\n", "[::1]", "[::1]"],
+  ["\t[::1]\r\n", "[::1]", "[::1]"],
+  ["[::\n1]", "[::1]", "[::1]"],
+  ["\t[::1]:80", "", ""],
+  ["a\t:80", "", ""],
+  ["\t", "", ""],
+  // The host ends at the first path, query, fragment or backslash; a port or userinfo fails.
+  ["a/b", "a", "a"],
+  ["a?b", "a", "a"],
+  ["a#b", "a", "a"],
+  ["a\\b", "a", "a"],
+  ["a:80", "", ""],
+  ["a@b", "", ""],
+  // Valid domains are preserved (CheckHyphens and VerifyDnsLength are off).
+  ["example.com", "example.com", "example.com"],
+  ["b\u00fccher.de", "xn--bcher-kva.de", "b\u00fccher.de"],
+  ["\u00e7.com", "xn--7ca.com", "\u00e7.com"],
+  ["a..b", "a..b", "a..b"],
+  [".", ".", "."],
+  ["..", "..", ".."],
+  ["example.com.", "example.com.", "example.com."],
+  ["a_b.example", "a_b.example", "a_b.example"],
+  ["a-.example", "a-.example", "a-.example"],
+  ["-a.example", "-a.example", "-a.example"],
+  ["ab--c.example", "ab--c.example", "ab--c.example"],
+  ["r4---sn-a5mlrn7s.gevideo.com", "r4---sn-a5mlrn7s.gevideo.com", "r4---sn-a5mlrn7s.gevideo.com"],
+  // UTS #46 mapping, deviation characters (nontransitional) and CONTEXTJ. A non-ASCII host still goes through
+  // the full UTS #46 processing, so an xn-- label with a non-ASCII character in it fails.
+  ["x\u200bn--a.example", "", ""],
+  ["xn--te\u0161la", "", ""],
+  ["fa\u00df.de", "xn--fa-hia.de", "fa\u00df.de"],
+  ["\u0130.com", "xn--i-9bb.com", "i\u0307.com"],
+  ["\u03c2.com", "xn--3xa.com", "\u03c2.com"],
+  ["\u30c6\u30b9\u30c8.example", "xn--zckzah.example", "\u30c6\u30b9\u30c8.example"],
+  ["look\u200cout.net", "", ""],
+  ["", "", ""],
+];
+
+describe("WHATWG host parser parity", () => {
+  for (const [input, ascii, unicode] of hostParserParity) {
+    test(JSON.stringify(input), () => {
+      expect({
+        ascii: url.domainToASCII(input),
+        unicode: url.domainToUnicode(input),
+      }).toEqual({ ascii, unicode });
+    });
+  }
+});
+
+// Unicode 16 moved these code points from disallowed to mapped or ignored. ICU 76 is the first release with that
+// table; macOS links the system ICU, which can be older.
+describe.skipIf(parseInt(process.versions.icu) < 76)("Unicode 16 UTS #46 table", () => {
+  test("domainToASCII maps the reclassified code points", () => {
+    expect(
+      [
+        "\u04C0", // CYRILLIC LETTER PALOCHKA
+        "\u10AC", // GEORGIAN CAPITAL LETTER NAR
+        "\u2132", // TURNED CAPITAL F
+        "\u2183", // ROMAN NUMERAL REVERSED ONE HUNDRED
+        "a\u180Eb", // MONGOLIAN VOWEL SEPARATOR, now ignored
+        "a\u3164b", // HANGUL FILLER, now ignored
+      ].map(domain => url.domainToASCII(domain)),
+    ).toEqual(["xn--s5a", "xn--3kj", "xn--73g", "xn--r5g", "ab", "ab"]);
+  });
+});
diff --git a/test/js/web/url/url.test.ts b/test/js/web/url/url.test.ts
index 3857ed3e9ac0..9a6b3588de76 100755
--- a/test/js/web/url/url.test.ts
+++ b/test/js/web/url/url.test.ts
@@ -138,6 +138,38 @@ describe("url", () => {
     const hn = new URL("http://x/");
     hn.hostname = "\u04C0.com";
     expect(hn.hostname).toBe("xn--s5a.com");
+
+    // Capitals whose UTS #46 status went from disallowed to mapped, and format
+    // controls that became ignored. Expected values are Node's.
+    expect(
+      [
+        "\u10AC", // GEORGIAN CAPITAL LETTER NAR
+        "a\u10B5", // GEORGIAN CAPITAL LETTER KHAR
+        "\u2132", // TURNED CAPITAL F
+        "\u2183", // ROMAN NUMERAL REVERSED ONE HUNDRED
+        "\uA846\u3002\u2183\u0FB5\uB1AE-", // WPT IdnaTestV2; U+3002 is a label separator
+        "a\u2061b", // FUNCTION APPLICATION
+        "a\u3164b", // HANGUL FILLER
+      ].map(host => new URL(`https://${host}/`).hostname),
+    ).toEqual(["xn--3kj", "xn--a-hws", "xn--73g", "xn--r5g", "xn--fc9a.xn----qmg097k469k", "ab", "ab"]);
+  });
+
+  it("keeps valid xn-- labels, and hosts that only contain the letters xn--", () => {
+    const accepted = {
+      "http://xn--bcher-kva.de/": "xn--bcher-kva.de",
+      "http://XN--BCHER-KVA.DE/": "xn--bcher-kva.de",
+      "http://xn--fiqs8s/": "xn--fiqs8s",
+      "http://xn--e1afmkfd.xn--p1ai/": "xn--e1afmkfd.xn--p1ai",
+      // Not a punycode label: "xn--" is not at the start of it.
+      "http://axn--a-ecp.example/": "axn--a-ecp.example",
+      // xn-- outside the host is not looked at. ("xn--a-ecp" is not valid punycode.)
+      "http://xn--a-ecp@ok.example/": "ok.example",
+      "http://user:pw@xn--bcher-kva.de:8080/xn--a-ecp?xn--a-ecp#xn--a-ecp": "xn--bcher-kva.de",
+      // Hosts of non-special schemes are opaque: no IDNA, not even lowercasing.
+      "foo://xn--a-ecp.example/": "xn--a-ecp.example",
+      "foo://XN--A-ECP.example/": "XN--A-ECP.example",
+    };
+    expect(Object.fromEntries(Object.keys(accepted).map(input => [input, new URL(input).hostname]))).toEqual(accepted);
   });
 
   it("rejects invalid punycode labels however they are spelled in the input (like Node)", () => {