diff --git a/src/browser/browser.zig b/src/browser/browser.zig
index 635390c4..cc153870 100644
--- a/src/browser/browser.zig
+++ b/src/browser/browser.zig
@@ -214,6 +214,20 @@ pub const Page = struct {
         };
     }
 
+    // start js env.
+    pub fn start(self: *Page) !void {
+        // start JS env
+        log.debug("start js env", .{});
+        try self.session.env.start();
+
+        // register the module loader
+        try self.session.env.setModuleLoadFn(self.session, Session.fetchModule);
+
+        // add global objects
+        log.debug("setup global env", .{});
+        try self.session.env.bindGlobal(&self.session.window);
+    }
+
     // reset js env and mem arena.
     pub fn end(self: *Page) void {
         self.session.env.stop();
@@ -373,14 +387,6 @@ pub const Page = struct {
 
         // https://html.spec.whatwg.org/#read-html
 
-        // start JS env
-        // TODO load the js env concurrently with the HTML parsing.
-        log.debug("start js env", .{});
-        try self.session.env.start();
-
-        // register the module loader
-        try self.session.env.setModuleLoadFn(self.session, Session.fetchModule);
-
         // load polyfills
         try polyfill.load(alloc, self.session.env);
 
@@ -395,10 +401,6 @@ pub const Page = struct {
             .httpClient = &self.session.httpClient,
         });
 
-        // add global objects
-        log.debug("setup global env", .{});
-        try self.session.env.bindGlobal(&self.session.window);
-
         // browse the DOM tree to retrieve scripts
         // TODO execute the synchronous scripts during the HTL parsing.
         // TODO fetch the script resources concurrently but execute them in the
diff --git a/src/cdp/page.zig b/src/cdp/page.zig
index cf86297f..d453e9d5 100644
--- a/src/cdp/page.zig
+++ b/src/cdp/page.zig
@@ -331,8 +331,9 @@ fn navigate(
     // TODO: noop event, we have no env context at this point, is it necesarry?
     try sendEvent(alloc, ctx, "Runtime.executionContextsCleared", void, {}, input.sessionId);
 
-    // Launch navigate
-    const p = try ctx.browser.session.createPage();
+    // Launch navigate, the page must have been created by a
+    // target.createTarget.
+    var p = ctx.browser.session.page orelse return error.NoPage;
     ctx.state.executionContextId += 1;
     const auxData = try std.fmt.allocPrint(
         alloc,
diff --git a/src/cdp/target.zig b/src/cdp/target.zig
index 6d3c611b..048c1d68 100644
--- a/src/cdp/target.zig
+++ b/src/cdp/target.zig
@@ -344,6 +344,14 @@ fn createTarget(
     ctx.state.loaderID = LoaderID;
     ctx.state.sessionID = msg.sessionId;
 
+    // TODO stop the previous page instead?
+    if (ctx.browser.session.page != null) return error.pageAlreadyExists;
+
+    // create the page
+    const p = try ctx.browser.session.createPage();
+    // start the js env
+    try p.start();
+
     // send targetCreated event
     const created = TargetCreated{
         .sessionId = cdp.ContextSessionID,
@@ -440,6 +448,8 @@ fn closeTarget(
         null,
     );
 
+    if (ctx.browser.session.page != null) ctx.browser.session.page.?.end();
+
     return "";
 }
 
diff --git a/src/main.zig b/src/main.zig
index 84e23536..787f1501 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -326,6 +326,8 @@ pub fn main() !void {
 
             // page
             const page = try browser.session.createPage();
+            try page.start();
+            defer page.end();
 
             _ = page.navigate(opts.url, null) catch |err| switch (err) {
                 error.UnsupportedUriScheme, error.UriMissingHost => {