diff --git a/packages/playwright-core/src/cli/cli.ts b/packages/playwright-core/src/cli/cli.ts
index e1b7ad9196..1f46497086 100755
--- a/packages/playwright-core/src/cli/cli.ts
+++ b/packages/playwright-core/src/cli/cli.ts
@@ -218,7 +218,7 @@ program
         options.browser = 'firefox';
       if (options.browser === 'wk')
         options.browser = 'webkit';
-      showTraceViewer(trace, options.browser).catch(logErrorAndExit);
+      showTraceViewer(trace, options.browser, false, 9322).catch(logErrorAndExit);
     }).addHelpText('afterAll', `
 Examples:
 
diff --git a/packages/playwright-core/src/server/trace/viewer/traceViewer.ts b/packages/playwright-core/src/server/trace/viewer/traceViewer.ts
index 96cc10bd0c..a452d48d7c 100644
--- a/packages/playwright-core/src/server/trace/viewer/traceViewer.ts
+++ b/packages/playwright-core/src/server/trace/viewer/traceViewer.ts
@@ -25,7 +25,7 @@ import { internalCallMetadata } from '../../instrumentation';
 import { createPlaywright } from '../../playwright';
 import { ProgressController } from '../../progress';
 
-export async function showTraceViewer(traceUrl: string, browserName: string, headless = false): Promise<BrowserContext | undefined> {
+export async function showTraceViewer(traceUrl: string, browserName: string, headless = false, port?: number): Promise<BrowserContext | undefined> {
   const server = new HttpServer();
   server.routePath('/file', (request, response) => {
     try {
@@ -42,7 +42,7 @@ export async function showTraceViewer(traceUrl: string, browserName: string, hea
     return server.serveFile(response, absolutePath);
   });
 
-  const urlPrefix = await server.start();
+  const urlPrefix = await server.start(port);
 
   const traceViewerPlaywright = createPlaywright('javascript', true);
   const traceViewerBrowser = isUnderTest() ? 'chromium' : browserName;
diff --git a/packages/playwright-core/src/web/traceViewer/sw.ts b/packages/playwright-core/src/web/traceViewer/sw.ts
index b40394290d..8e7880904d 100644
--- a/packages/playwright-core/src/web/traceViewer/sw.ts
+++ b/packages/playwright-core/src/web/traceViewer/sw.ts
@@ -28,53 +28,86 @@ self.addEventListener('activate', function(event: any) {
   event.waitUntil(self.clients.claim());
 });
 
-let traceModel: TraceModel | undefined;
-let snapshotServer: SnapshotServer | undefined;
 const scopePath = new URL(self.registration.scope).pathname;
 
-async function loadTrace(trace: string): Promise<TraceModel> {
+const loadedTraces = new Map<string, { traceModel: TraceModel, snapshotServer: SnapshotServer, clientId: string }>();
+
+async function loadTrace(trace: string, clientId: string): Promise<TraceModel> {
+  const entry = loadedTraces.get(trace);
+  if (entry)
+    return entry.traceModel;
   const traceModel = new TraceModel();
   const url = trace.startsWith('http') || trace.startsWith('blob') ? trace : `/file?path=${trace}`;
   await traceModel.load(url);
+  const snapshotServer = new SnapshotServer(traceModel.storage());
+  loadedTraces.set(trace, { traceModel, snapshotServer, clientId });
   return traceModel;
 }
 
 // @ts-ignore
 async function doFetch(event: FetchEvent): Promise<Response> {
   const request = event.request;
-  const url = new URL(request.url);
   const snapshotUrl = request.mode === 'navigate' ?
     request.url : (await self.clients.get(event.clientId))!.url;
+  const traceUrl = new URL(snapshotUrl).searchParams.get('trace')!;
+  const { snapshotServer } = loadedTraces.get(traceUrl) || {};
 
   if (request.url.startsWith(self.registration.scope)) {
+    const url = new URL(request.url);
+
     const relativePath = url.pathname.substring(scopePath.length - 1);
     if (relativePath === '/context') {
-      const trace = url.searchParams.get('trace')!;
-      traceModel = await loadTrace(trace);
-      snapshotServer = new SnapshotServer(traceModel.storage());
+      await gc();
+      const traceModel = await loadTrace(traceUrl, event.clientId);
       return new Response(JSON.stringify(traceModel!.contextEntry), {
         status: 200,
         headers: { 'Content-Type': 'application/json' }
       });
     }
-    if (relativePath.startsWith('/snapshotSize/'))
-      return snapshotServer!.serveSnapshotSize(relativePath, url.searchParams);
-    if (relativePath.startsWith('/snapshot/'))
-      return snapshotServer!.serveSnapshot(relativePath, url.searchParams, snapshotUrl);
-    if (relativePath.startsWith('/sha1/')) {
-      const blob = await traceModel!.resourceForSha1(relativePath.slice('/sha1/'.length));
-      if (blob)
-        return new Response(blob, { status: 200 });
-      else
+
+    if (relativePath.startsWith('/snapshotSize/')) {
+      if (!snapshotServer)
         return new Response(null, { status: 404 });
+      return snapshotServer.serveSnapshotSize(relativePath, url.searchParams);
     }
+
+    if (relativePath.startsWith('/snapshot/')) {
+      if (!snapshotServer)
+        return new Response(null, { status: 404 });
+      return snapshotServer.serveSnapshot(relativePath, url.searchParams, snapshotUrl);
+    }
+
+    if (relativePath.startsWith('/sha1/')) {
+      // Sha1 is unique, load it from either of the models for simplicity.
+      for (const { traceModel } of loadedTraces.values()) {
+        const blob = await traceModel!.resourceForSha1(relativePath.slice('/sha1/'.length));
+        if (blob)
+          return new Response(blob, { status: 200 });
+      }
+      return new Response(null, { status: 404 });
+    }
+
+    // Fallback to network.
     return fetch(event.request);
   }
 
-
   if (!snapshotServer)
     return new Response(null, { status: 404 });
-  return snapshotServer!.serveResource(request.url, snapshotUrl);
+  return snapshotServer.serveResource(request.url, snapshotUrl);
+}
+
+async function gc() {
+  const usedTraces = new Set<string>();
+  for (const [traceUrl, entry] of loadedTraces) {
+    const client = await self.clients.get(entry.clientId);
+    if (client)
+      usedTraces.add(traceUrl);
+  }
+
+  for (const traceUrl of loadedTraces.keys()) {
+    if (!usedTraces.has(traceUrl))
+      loadedTraces.delete(traceUrl);
+  }
 }
 
 // @ts-ignore
diff --git a/packages/playwright-core/src/web/traceViewer/ui/snapshotTab.tsx b/packages/playwright-core/src/web/traceViewer/ui/snapshotTab.tsx
index b0b460d1da..edce0c1ddd 100644
--- a/packages/playwright-core/src/web/traceViewer/ui/snapshotTab.tsx
+++ b/packages/playwright-core/src/web/traceViewer/ui/snapshotTab.tsx
@@ -41,8 +41,9 @@ export const SnapshotTab: React.FunctionComponent<{
   if (action) {
     const snapshot = snapshots[snapshotIndex];
     if (snapshot && snapshot.snapshotName) {
-      snapshotUrl = new URL(`snapshot/${action.metadata.pageId}?name=${snapshot.snapshotName}`, window.location.href).toString();
-      snapshotSizeUrl = new URL(`snapshotSize/${action.metadata.pageId}?name=${snapshot.snapshotName}`, window.location.href).toString();
+      const traceUrl = new URL(window.location.href).searchParams.get('trace');
+      snapshotUrl = new URL(`snapshot/${action.metadata.pageId}?trace=${traceUrl}&name=${snapshot.snapshotName}`, window.location.href).toString();
+      snapshotSizeUrl = new URL(`snapshotSize/${action.metadata.pageId}?trace=${traceUrl}&name=${snapshot.snapshotName}`, window.location.href).toString();
       if (snapshot.snapshotName.includes('action')) {
         pointX = action.metadata.point?.x;
         pointY = action.metadata.point?.y;
diff --git a/packages/playwright-test/src/reporters/html.ts b/packages/playwright-test/src/reporters/html.ts
index 1c24f98085..dc4231a77c 100644
--- a/packages/playwright-test/src/reporters/html.ts
+++ b/packages/playwright-test/src/reporters/html.ts
@@ -127,7 +127,7 @@ class HtmlReporter {
         const absolutePath = path.join(reportFolder, ...relativePath.split('/'));
         return server.serveFile(response, absolutePath);
       });
-      const url = await server.start();
+      const url = await server.start(9323);
       console.log('');
       console.log(colors.cyan(`  Serving HTML report at ${url}. Press Ctrl+C to quit.`));
       console.log('');