Keep a control fixed to the viewport during scrolling.
CSS: Fixed positioning normally uses the viewport when no ancestor establishes a different fixed containing block.
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>Example</title>
<style>
button { position:fixed; top:10px; right:10px; } .space { height:2000px; }
</style>
</head>
<body>
<button>Top</button><div class="space"></div>
</body>
</html>Expected output EXAMPLE
At a 1000 × 800 CSS-pixel viewport, unless another size is stated: The fixed button stays 10 pixels below the viewport's top edge, including after scrolling the page down 500 pixels.
Details
Save this complete fixture as example.html. The output describes layout or computed styles verified in Chromium. Fixed positioning normally uses the viewport when no ancestor establishes a different fixed containing block.
Tested on Ubuntu 24.04.5 LTS · · Chromium 141.0.7390.37 · libc6 2.39-0ubuntu8.9; Playwright 1.56.0
Test inputs, results and environment
The exact published code ran in a dedicated Linux test container with prepared inputs. Unprivileged snippet process, external networking disabled, read-only root filesystem, and a fresh temporary working directory. Fixtures and output records are isolated from the application database. Testing covers this example and its stated checks, not every input, operating system, or runtime version. The Linux container shares its host's kernel; this is not a native Windows test.
- Architecture / host kernel
- x86_64 / 6.18.54.1-microsoft-standard-WSL2
- Snippet identity / locale
- uid=65534, gid=65534 (unprivileged) / C.UTF-8
- Interpreter invocation
Chromium: open example.html; execute the published browser assertions- Container image ID
sha256:32dc2d998158b6554c99b73b533f423696a0f3e31e8cbea9db10b5eee9a2fadd- Code SHA-256
328e08900c8a3830550d72ed2c0110e6d68d74515f258262b98fbeba7c8051c2- Dependencies
- libc6 2.39-0ubuntu8.9; Playwright 1.56.0
Test input setup
These are the prepared inputs used by the test harness. See Details above for the prerequisites and how to run this example.
# No input files required.
Observed standard output
Expected output describes the rendered page. The standard-output record below is the browser test harness receipt; the additional assertions check the result and interactions.
Keep a control fixed to the viewport during scrolling: browser checks passed.
Exit code: 0. Standard error: empty. Validation: Shape/content assertions. System-dependent values above are one recorded run.
Additional assertions that passed
Checks recorded by the test harness. Where Python assertions are shown, browser cases use Playwright and simulator cases may inspect pin transitions: result.stdout is captured output, work is the temporary directory, and Path is pathlib.Path. The harness also imports json and csv.
before=await page.locator('button').bounding_box()
await page.evaluate('window.scrollTo(0,500)')
after=await page.locator('button').bounding_box()
assert before['y']==after['y']==10