Playwright .NET 1.64 adds Locator.Within(), and it is Locator chaining read backwards

Microsoft.Playwright 1.64.0 hit NuGet on October 21, 2026, followed by 1.64.1 a day later with a bundled Node.js 24.22.1 bump. The release ships Chromium 156, Firefox 157 and WebKit 27.2, WebMCP testing and VP9 screencasts, but the API most test suites will touch first is Locator.Within().

Child first, parent second

Within(ILocator) returns a locator that matches the current locator’s elements inside each element matched by the argument. The point is reading order. When you already hold two locators, you can now say “this button, within that dialog” instead of building the chain from the outside in:

var save = page.GetByRole(AriaRole.Button, new() { Name = "Save" });
var dialog = page.GetByTestId("settings-dialog");

// 1.64+
await save.Within(dialog).ClickAsync();

// Before 1.64
await dialog.Locator(save).ClickAsync();

Relative locators like Nth() and First are resolved inside each parent separately, which is what makes column queries work:

var thirdColumn = page.GetByRole(AriaRole.Cell).Nth(2)
    .Within(page.GetByRole(AriaRole.Row));

await Expect(thirdColumn).ToHaveTextAsync(new[] { "Apple", "Banana", "Cherry" });

What it compiles down to

I ran both forms against Chromium 156 with Microsoft.Playwright 1.64.1 on .NET SDK 10.0.302, using a three-row table and a page with two “Save” buttons (one in a dialog, one in a form). The results:

ToString() settles it: cells.Nth(2).Within(rows) prints GetByRole(AriaRole.Row).Locator(GetByRole(AriaRole.Cell).Nth(2)), character for character the same as the old chain. Within() is not a new matching engine. It is the existing Locator(ILocator) overload with the arguments swapped, and error messages and trace viewer entries will show the chained form.

That has two practical consequences:

• No behavior change to migrate. If your suite already uses parent.Locator(childLocator), the per-parent Nth() semantics were already there. Switching to Within() is purely about readability, especially in page objects that expose child locators and let callers pick the scope.
• The real trap is still where Nth() sits. rows.Locator("td").Nth(2) applies Nth(2) to the flattened result and gives you one cell. Put Nth() on the inner locator (or use Within(), which nudges you to) when you want one match per parent.

The breaking change in the same release

1.64 also changes visibility: elements inside an iframe that is itself not visible, for example visibility: hidden, are now considered hidden by actions, IsVisibleAsync() and ToBeVisibleAsync(). If a test clicked through a hidden frame by accident, it will now time out waiting for visibility. That is worth checking before you bump, more than Within() is.

Upgrade with:

dotnet add package Microsoft.Playwright --version 1.64.1
pwsh bin/Debug/net10.0/playwright.ps1 install

Note that the install step removes browser builds from older Playwright versions it considers unused, so another project on an older version may need to run its own install again. If you lean on Playwright for agent-driven UI tests, the selector discipline in self-healing E2E tests when a coding agent renames selectors pairs well with scoped locators like these.