Screen capture isn't working: here's why, and the fix

This is part of the answers hub on capture and feedback problems. If screen capture isn't producing anything, work down this list. The causes are ordered by how often they're the real problem.

1. The page isn't on HTTPS

Browser screen capture runs only in a secure context. That means HTTPS, or localhost during development. On a plain http:// URL the capture call fails without a visible error and the share prompt never appears.

Fix: load the page over HTTPS. If you're testing locally, localhost and 127.0.0.1 count as secure and will work.

2. The browser doesn't support it

Capture needs a current desktop browser: Chrome, Edge, Firefox, or Safari 13+. Older browsers, in-app webviews (the browser inside a native app like Slack or a mail client), and most mobile browsers either lack the API or restrict it.

Fix: open the page in a full desktop browser rather than an embedded webview, and update if you're several versions behind.

3. Permission was denied or revoked

If you clicked Block on a previous share prompt, the browser remembers and refuses silently. Cleared site data does the same.

Fix: click the permissions icon to the left of the address bar, reset screen-sharing for the site, and reload. The dedicated page on permission-denied errors walks through this per browser.

4. You picked a protected window

Capture can start successfully and still produce a black frame if the selected window is OS-protected: DRM video, some password managers, some banking apps. The browser isn't broken; the content is deliberately shielded.

Fix: capture a different window, or the whole screen, and see capturing protected content.

Still stuck?

If none of the above match, the capture API is likely fine and the problem is downstream (the image is captured but unusable). The two common downstream issues are a blurry result and an agent that can't read the screenshot.

Frequently asked questions

Why does the screen-share prompt never appear?

The most common reason is that the page isn't served over HTTPS. The browser screen-capture API only runs in a secure context (HTTPS or localhost). On plain HTTP, the call fails silently and no prompt shows. The next most common reason is an unsupported browser: capture needs a current Chrome, Edge, Firefox, or Safari.

It worked yesterday and stopped today. What changed?

Usually a revoked permission. If you clicked 'Block' on the share prompt, or cleared site permissions, the browser will refuse silently until you re-grant access in the site permissions panel (the icon to the left of the address bar).

Does screen capture work on mobile?

Largely no. iOS Safari does not support tab or screen capture via the web API at all, and Android support is partial and device-dependent. Screen capture is a desktop-first feature.

Capture starts but the image is a black rectangle. Why?

That's an OS or app protection on the window you selected. DRM-protected video players and some banking or password apps render as black on capture by design. See the page on capturing protected windows.