diff --git a/packages/playwright-core/src/server/trace/viewer/traceViewer.ts b/packages/playwright-core/src/server/trace/viewer/traceViewer.ts
index 0e83a15f387f7..39ea55ee0f026 100644
--- a/packages/playwright-core/src/server/trace/viewer/traceViewer.ts
+++ b/packages/playwright-core/src/server/trace/viewer/traceViewer.ts
@@ -55,7 +55,7 @@ export type TraceViewerAppOptions = {
 
 const tracesDirMarker = 'traces.dir';
 
-function validateTraceUrl(traceFileOrUrl: string | undefined): string | undefined {
+function validateTraceUrlOrPath(traceFileOrUrl: string | undefined): string | undefined {
   if (!traceFileOrUrl)
     return traceFileOrUrl;
 
@@ -152,7 +152,7 @@ export async function installRootRedirect(server: HttpServer, traceUrl: string |
 }
 
 export async function runTraceViewerApp(traceUrl: string | undefined, browserName: string, options: TraceViewerServerOptions & { headless?: boolean }, exitOnClose?: boolean) {
-  traceUrl = validateTraceUrl(traceUrl);
+  traceUrl = validateTraceUrlOrPath(traceUrl);
   const server = await startTraceViewerServer(options);
   await installRootRedirect(server, traceUrl, options);
   const page = await openTraceViewerApp(server.urlPrefix('precise'), browserName, options);
@@ -162,7 +162,7 @@ export async function runTraceViewerApp(traceUrl: string | undefined, browserNam
 }
 
 export async function runTraceInBrowser(traceUrl: string | undefined, options: TraceViewerServerOptions) {
-  traceUrl = validateTraceUrl(traceUrl);
+  traceUrl = validateTraceUrlOrPath(traceUrl);
   const server = await startTraceViewerServer(options);
   await installRootRedirect(server, traceUrl, options);
   await openTraceInBrowser(server.urlPrefix('human-readable'));
@@ -216,8 +216,8 @@ class StdinServer implements Transport {
 
   constructor() {
     process.stdin.on('data', data => {
-      const url = data.toString().trim();
-      if (url === this._traceUrl)
+      const url = validateTraceUrlOrPath(data.toString().trim());
+      if (!url || url === this._traceUrl)
         return;
       if (url.endsWith('.json'))
         this._pollLoadTrace(url);
diff --git a/packages/playwright-core/src/server/utils/httpServer.ts b/packages/playwright-core/src/server/utils/httpServer.ts
index 92a46aac1762f..cb08f27eb2e36 100644
--- a/packages/playwright-core/src/server/utils/httpServer.ts
+++ b/packages/playwright-core/src/server/utils/httpServer.ts
@@ -115,7 +115,7 @@ export class HttpServer {
       this._port = address.port;
       const resolvedHost = address.family === 'IPv4' ? address.address : `[${address.address}]`;
       this._urlPrefixPrecise = `http://${resolvedHost}:${address.port}`;
-      this._urlPrefixHumanReadable = `http://${host}:${address.port}`;
+      this._urlPrefixHumanReadable = `http://${host ?? 'localhost'}:${address.port}`;
     }
   }
 
diff --git a/tests/library/trace-viewer.spec.ts b/tests/library/trace-viewer.spec.ts
index 0e03f7fb1d094..706197fb0e1d6 100644
--- a/tests/library/trace-viewer.spec.ts
+++ b/tests/library/trace-viewer.spec.ts
@@ -2248,3 +2248,16 @@ test('should capture iframe with srcdoc', async ({ page, server, runAndTrace })
   const frame = await traceViewer.snapshotFrame('Evaluate');
   await expect(frame.frameLocator('iframe').getByRole('button')).toHaveText('Hello iframe');
 });
+
+test('take trace paths via stdin', async ({ childProcess, page }) => {
+  const cliEntrypoint = path.join(__dirname, '../../packages/playwright-core/cli.js');
+  const cp = childProcess({ command: ['node', cliEntrypoint, 'show-trace', '--port', '0', '--stdin'] });
+  await cp.waitForOutput('Listening on');
+  const url = cp.output.match(/Listening on (http:\/\/[^\s]+)/)![1];
+  await page.goto(url);
+  await expect(page).toHaveTitle('Playwright Trace Viewer');
+  cp.write(traceFile);
+  await expect(page.locator('.action-title')).toContainText([
+    /Create page/,
+  ]);
+});