Screen share check
Published
See in one minute whether your browser can share a screen, a window or a tab. The page checks support, starts a real sharing session with a local preview and tells you what each result and error means. The picture is never recorded or uploaded.
The preview is drawn in this page only. It is not recorded, uploaded or stored, and no audio is captured.
How to use the check
- Read the three lines at the top. They tell you whether the page is secure, whether your browser has the screen-capture feature and whether you appear to be on a phone.
- Press Start sharing preview. The browser opens its own picker. This window belongs to the browser, not to the page, and the page cannot choose for you.
- Pick an entire screen, a window or a browser tab. On many systems the browser offers all three; on some only tabs and windows.
- Look at the preview. The line under it shows what you are sharing, the size and the frame rate. Move a window to see the preview follow it.
- Press Stop sharing, or use the stop button that the browser shows, when you are done.
How to read the results
Secure connection
Browsers only allow screen capture on pages served over HTTPS (or on the local machine during development). If this line fails, you are looking at a copy of the page over an insecure connection or inside a frame that does not allow capture.
Screen capture supported
This line tells you whether your browser has the feature at all. On desktop it is available in current Chrome, Edge, Firefox and Safari. According to the browser compatibility data kept by MDN, Chrome and Firefox on Android do not support it, and Safari on iPhone and iPad added it only in very recent versions, so a phone usually fails here. That is a browser limit, not a setting you can change.
What you chose to share
The preview line names the kind of source: entire screen, window or browser tab. Sharing a tab is the lightest and the most private option, because other windows stay hidden. Sharing the entire screen shows everything, including notifications, so close private messages first.
Preview of yourself in a mirror
If you share the screen or window that shows this preview, the picture repeats itself like a tunnel. That is expected and shows the capture is live.
What each error means and how to fix it
NotAllowedError
The most common error. It appears when you press Cancel in the picker, so cancelling is not a fault. It also appears when the operating system has not given your browser permission to record the screen. On a Mac, screen recording is a privacy permission that you grant to each app in the system settings, and the browser usually has to be restarted afterwards; the article on camera and microphone privacy settings shows where those system settings live. A work policy can also forbid sharing.
InvalidStateError
Browsers require that screen capture starts from a real click or tap. Pressing the button yourself, rather than from a script or a delayed action, avoids it.
NotFoundError and NotReadableError
Not found means the system offered no source to capture, for example on a remote desktop session with no display. Not readable means the source exists but cannot be read, often because of a driver or operating-system lock. Choose another source, close other capture programs and restart the browser.
Nothing happens at all
A blocked pop-up area, a browser extension that intercepts capture or an embedded view can swallow the picker. Open the page in a normal browser tab and try again.
Browser and device differences
- Desktop browsers show their own picker, and what it offers (entire screen, window, tab) depends on the browser and the operating system. The picker is drawn by the browser, so its look differs between browsers.
- Phones and tablets: sharing the screen from a web page is generally not available. Apps that share a phone screen use a separate operating-system feature, not the web page.
- Audio: this check asks for video only. Whether a browser can also share sound depends on the browser, the operating system and what you pick, and calling services may ask for it differently.
- Calling services can set their own preferences for the picker, such as which source is suggested first. This check uses the browser's defaults.
Privacy: what happens to the shared picture
The page puts the captured picture into a video element and does nothing else with it. It is not recorded, uploaded or stored, and the check asks only for video, so no sound is captured. The browser shows its own indicator while sharing is active, and the capture ends when you press Stop, close the page or use the browser's stop button. Share a tab rather than the whole screen when you only need to show one thing.
Frequently asked questions
Why does the check say my phone is not supported?
Browsers on phones and tablets generally do not offer screen capture to web pages. It is a limitation of mobile browsers, not of this site.
Can I share the sound of my computer?
This check asks for video only. Some desktop browsers can share the audio of a tab or the system when a call service asks for it, but support varies.
Does pressing Cancel mean something is broken?
No. Cancel returns a permission error because you declined. Press the button again and choose a source.
Is my screen recorded?
No. The picture is shown live in this page and then discarded. Nothing is uploaded or saved.
References
Official documentation used to check this article. Pages are maintained by their owners and may change.
Reviewed against ChatLite's current behavior on .