diff --git a/src/lib/router.ts b/src/lib/router.ts
index 285d1e61a..688fbf5da 100644
--- a/src/lib/router.ts
+++ b/src/lib/router.ts
@@ -243,4 +243,4 @@ export function routeToPath(route: Route): string {
   }
 }
 
-export const testExports = { urlToRoute, routeToPath };
+export const testExports = { urlToRoute, routeToPath, extractBaseUrl };
diff --git a/src/lib/utils.ts b/src/lib/utils.ts
index 5c5c3eb87..a6c5f71d5 100644
--- a/src/lib/utils.ts
+++ b/src/lib/utils.ts
@@ -203,9 +203,9 @@ export function isMarkdownPath(path: string): boolean {
   return /\.(md|mkd|markdown)$/i.test(path);
 }
 
-// Check whether the given address is a localhost address.
 export function isLocal(addr: string): boolean {
-  return addr.startsWith("127.0.0.1") || addr.startsWith("localhost");
+  // Support *.localhost subdomains and 127.0.0.1.
+  return addr.endsWith("localhost") || addr.startsWith("127.0.0.1");
 }
 
 // Check whether the given domain name is an onion domain name.
diff --git a/tests/unit/router.test.ts b/tests/unit/router.test.ts
index e220f816b..b08e3d7ff 100644
--- a/tests/unit/router.test.ts
+++ b/tests/unit/router.test.ts
@@ -269,3 +269,95 @@ describe("pathToRoute", () => {
     ).toEqual(route);
   }
 });
+
+describe("extractBaseUrl", () => {
+  test("hostname with explicit port", () => {
+    const result = testExports.extractBaseUrl("example.com:9000");
+    expect(result).toEqual({
+      hostname: "example.com",
+      port: 9000,
+      scheme: config.nodes.defaultHttpdScheme,
+    });
+  });
+
+  test("hostname without port uses default port and scheme", () => {
+    const result = testExports.extractBaseUrl("example.com");
+    expect(result).toEqual({
+      hostname: "example.com",
+      port: config.nodes.defaultHttpdPort,
+      scheme: config.nodes.defaultHttpdScheme,
+    });
+  });
+
+  test("localhost without port uses local port and http scheme", () => {
+    const result = testExports.extractBaseUrl("localhost");
+    expect(result).toEqual({
+      hostname: "localhost",
+      port: config.nodes.defaultLocalHttpdPort,
+      scheme: "http",
+    });
+  });
+
+  test("localhost with explicit port uses http scheme", () => {
+    const result = testExports.extractBaseUrl("localhost:3000");
+    expect(result).toEqual({
+      hostname: "localhost",
+      port: 3000,
+      scheme: "http",
+    });
+  });
+
+  test("wildcard localhost domain without port uses local port and http scheme", () => {
+    const result = testExports.extractBaseUrl("app.localhost");
+    expect(result).toEqual({
+      hostname: "app.localhost",
+      port: config.nodes.defaultLocalHttpdPort,
+      scheme: "http",
+    });
+  });
+
+  test("127.0.0.1 without port uses local port and http scheme", () => {
+    const result = testExports.extractBaseUrl("127.0.0.1");
+    expect(result).toEqual({
+      hostname: "127.0.0.1",
+      port: config.nodes.defaultLocalHttpdPort,
+      scheme: "http",
+    });
+  });
+
+  test("127.0.0.1 with explicit port uses http scheme", () => {
+    const result = testExports.extractBaseUrl("127.0.0.1:8080");
+    expect(result).toEqual({
+      hostname: "127.0.0.1",
+      port: 8080,
+      scheme: "http",
+    });
+  });
+
+  test("onion domain without port uses default port and http scheme", () => {
+    const result = testExports.extractBaseUrl("example.onion");
+    expect(result).toEqual({
+      hostname: "example.onion",
+      port: config.nodes.defaultHttpdPort,
+      scheme: "http",
+    });
+  });
+
+  test("onion domain with explicit port uses http scheme", () => {
+    const result = testExports.extractBaseUrl("example.onion:9050");
+    expect(result).toEqual({
+      hostname: "example.onion",
+      port: 9050,
+      scheme: "http",
+    });
+  });
+
+  test("URL-encoded hostname is decoded", () => {
+    const result = testExports.extractBaseUrl("example.com%3A8000");
+    expect(result).toEqual({
+      hostname: "example.com",
+      port: 8000,
+      scheme: config.nodes.defaultHttpdScheme,
+    });
+  });
+});
diff --git a/tests/unit/utils.test.ts b/tests/unit/utils.test.ts
index 85446a33a..9cabb63b5 100644
--- a/tests/unit/utils.test.ts
+++ b/tests/unit/utils.test.ts
@@ -234,3 +234,23 @@ describe("Date Manipulation", () => {
     );
   });
 });
+
+describe("isLocal", () => {
+  test("returns true for localhost", () => {
+    expect(utils.isLocal("localhost")).toBe(true);
+  });
+
+  test("returns true for 127.0.0.1", () => {
+    expect(utils.isLocal("127.0.0.1")).toBe(true);
+  });
+
+  test("returns true for localhost subdomains", () => {
+    expect(utils.isLocal("test.localhost")).toBe(true);
+    expect(utils.isLocal("deeper.test.localhost")).toBe(true);
+  });
+
+  test("returns false for any other tld", () => {
+    expect(utils.isLocal("example.com")).toBe(false);
+    expect(utils.isLocal("radicle.garden")).toBe(false);
+  });
+});