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A webpage captures video of a screen, browser tab, or window by asking the browser for permission with navigator.mediaDevices.getDisplayMedia(). The browser—not the webpage—shows a picker so you can choose what to share. If you approve, the page receives a MediaStream that it can preview, record with MediaRecorder, or send live through WebRTC.
What happens when a webpage captures video?
- A user action starts the request. A page usually calls
getDisplayMedia()after you click a button. The API requires transient user activation and a secure context in browsers that support it. MDN documents the method and its requirements. - The browser opens its own source picker. You choose a tab, window, or screen and approve sharing. Options supplied by the page may influence capture, but they cannot silently choose the source for you or remove the browser’s permission boundary. A fresh request requires fresh user permission.
- The browser returns a stream. If you approve, the promise resolves to a
MediaStreamwith a video track for the selected display surface. The page can attach it to a video element for preview. - The page uses the stream. It can record the stream, transmit it live, or simply show it in the page. The stream is not automatically a saved video file: the website has to implement recording or transmission.
- Sharing or recording ends. You or the page can stop the stream, and the selected source can end. The recording interface should make the active state and stop control clear.
This is the browser workflow described by MDN’s Screen Capture API overview and screen-capture guide.
What can the webpage do with the captured stream?
Preview it in the page
A website can assign the stream to a video element so you see what is being shared. Previewing does not by itself create a downloadable recording.
Record it with MediaRecorder
MediaRecorder accepts a media stream and emits recorded media data. A site can collect those data chunks and offer them as a file. Which recording formats and codecs work depends on the browser; a site should check support rather than assume one format is universal. See MDN’s MediaRecorder documentation.
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Guermok Video Capture Card, 4K USB3.0 HDMI to USB C, 1080P 60FPS & 2K 30FPS
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Send it live with WebRTC
A site can send the stream through WebRTC for live sharing or conferencing. Unlike a local preview or recording, this path sends media to another participant or service. The capture API supplies the stream; the website’s WebRTC implementation determines how it is transmitted.
| Use | What happens | Does the capture API save a file? |
|---|---|---|
| Preview | The page displays the selected surface in a video element. | No, not by itself. |
| Record | The page records the stream with MediaRecorder and handles the resulting data. | The page must implement recording and file handling. |
| Live transmission | The page sends the stream to another participant or service, commonly using WebRTC. | No; this is a live-delivery path. |
There is no universal quality or performance winner among these paths. The appropriate choice depends on whether you want local viewing, a saved recording, or live sharing, as well as the target browsers and their supported formats.
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- 【What You Get】Includes: HDMI Capture Card, USB 3.0 to USB-C Adapter, User Manual. Tips: Make sure your tablet’s OTG function is enabled before connecting. Test your HDMI device with a monitor first to confirm video and audio output, then connect to the Video Capture Card for recording.
Can a webpage capture a browser tab or the whole screen?
The browser’s picker lets the user choose an available source, such as a tab, window, or screen. The webpage cannot use options to bypass that choice or secretly begin capturing. The exact picker choices and behavior depend on the browser and operating system, so test the browsers your users rely on.
Even when a page asks to capture a particular kind of surface, the browser remains responsible for the selection and permission prompt. A grant is not a silent, permanent authorization that the site can reuse on a later call.
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Can screen recording in a browser include audio?
A page may request audio along with video, but requesting it does not guarantee that audio will be available. Depending on the browser and the selected source, audio may come from the shared surface, computer audio, or a microphone. Some sources or browsers do not provide the requested audio track.
Check the returned stream for the tracks it actually contains and test the exact browser, operating system, and source combination you plan to support. If narration is needed, a microphone is an optional audio source; it is not required for screen-video capture.
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Example: capture and record a screen in JavaScript
Run this code from a secure context, such as an HTTPS page, and call startCapture() directly from a button click. It requests video, previews the approved source, records it when MediaRecorder is available, and provides a download link when recording stops.
<button id="start">Choose screen and record</button>
<button id="stop" disabled>Stop</button>
<video id="preview" autoplay muted playsinline></video>
<a id="download" hidden>Download recording</a>
<script>
const startButton = document.querySelector('#start');
const stopButton = document.querySelector('#stop');
const preview = document.querySelector('#preview');
const download = document.querySelector('#download');
startButton.addEventListener('click', startCapture);
stopButton.addEventListener('click', stopCapture);
let stream;
let recorder;
let chunks = [];
async function startCapture() {
if (!navigator.mediaDevices?.getDisplayMedia) {
alert('Screen capture is not available in this browser.');
return;
}
if (!window.MediaRecorder) {
alert('Recording is not available in this browser.');
return;
}
try {
stream = await navigator.mediaDevices.getDisplayMedia({
video: true,
audio: true
});
preview.srcObject = stream;
chunks = [];
recorder = new MediaRecorder(stream);
recorder.addEventListener('dataavailable', event => {
if (event.data.size > 0) chunks.push(event.data);
});
recorder.addEventListener('stop', saveRecording);
recorder.start();
startButton.disabled = true;
stopButton.disabled = false;
stream.getVideoTracks()[0]?.addEventListener('ended', stopCapture, { once: true });
} catch (error) {
console.error('Screen capture failed:', error);
alert(`Could not start capture: ${error.message}`);
cleanup();
}
}
function stopCapture() {
if (recorder && recorder.state !== 'inactive') recorder.stop();
stream?.getTracks().forEach(track => track.stop());
cleanup();
}
function saveRecording() {
if (!chunks.length) return;
const type = recorder.mimeType || 'video/webm';
const blob = new Blob(chunks, { type });
const url = URL.createObjectURL(blob);
download.href = url;
download.download = 'screen-recording';
download.hidden = false;
}
function cleanup() {
startButton.disabled = false;
stopButton.disabled = true;
if (preview.srcObject) preview.srcObject = null;
stream = null;
}
</script>The example intentionally does not promise a particular file extension or codec. For a production implementation, check a proposed MIME type with MediaRecorder.isTypeSupported() in the target browser, use an extension that matches the chosen format, and release object URLs when they are no longer needed. The example requests audio, but the recording may contain no audio track if the selected source or browser does not provide one.
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Special offer. See more information about Outbyte and uninstall instructions. Please review EULA and Privacy policy.
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Requirements and privacy checks
- Secure context: Use HTTPS in deployment; support for the API is subject to secure-context rules.
- User activation: Call the API in direct response to a user gesture, such as clicking the capture button. Do not defer the request until after unrelated asynchronous work that may lose transient activation.
- Browser support: Feature-detect both
getDisplayMedia()andMediaRecorder, and check the formats your application needs. Availability and audio behavior vary across browsers. - Embedded pages: An iframe may need the
display-capturePermissions Policy permission. The browser still presents its user prompt; an iframe permission does not silently approve screen sharing. - Protect private information: Before choosing a surface, close or hide sensitive tabs, messages, account details, and password managers. A browser picker and sharing indicator help show what is being shared, but cannot judge whether every visible item is appropriate.
Troubleshooting common capture failures
| Symptom | Likely cause | What to check |
|---|---|---|
| The API is undefined or unavailable. | The browser does not support the feature, or the page is not in a secure context. | Feature-detect navigator.mediaDevices.getDisplayMedia; use HTTPS and verify support in the target browser. |
| The request fails before the picker appears. | The call did not occur during user activation, the options are invalid, or the browsing context disallows capture. | Call from the button handler, validate options, and check the embedding page’s Permissions Policy. |
| The user cancels or denies sharing. | The user dismissed the picker or declined permission. | Handle the rejected promise gracefully and let the user try again from an explicit button. A website cannot override this choice. |
| Video works but there is no audio. | The selected surface or browser did not supply an audio track. | Inspect the stream’s audio tracks and test the intended source and browser; do not assume audio: true guarantees sound. |
| Recording fails or the file will not play. | The browser may not support the assumed recorder format or codec. | Check MediaRecorder availability and MIME support, then use a supported format and matching file handling. |
| Capture stops unexpectedly. | The user stopped sharing, or the selected source ended. | Listen for track-ended and recorder-stop events, update the interface, and allow a new user-initiated capture. |
Or skip the browser setup
If what you need is a still screenshot or PDF of a webpage—not a recording of a user’s display—ScreenshotNeo is a website screenshot API and MCP server. Its one-call capture does not request display sharing from a visitor; it captures the supplied webpage URL.
cURL:
curl -G "https://api.screenshotneo.com/v1/shot" -d access_key=YOUR_API_KEY --data-urlencode url=https://stripe.com -o shot.webpSee the ScreenshotNeo API documentation for parameters. Python:
import requests
r = requests.get("https://api.screenshotneo.com/v1/shot", params={"access_key": "YOUR_API_KEY", "url": "https://stripe.com"}, timeout=90)
open("shot.webp", "wb").write(r.content)Node.js:
const q = new URLSearchParams({ access_key: 'YOUR_API_KEY', url: 'https://stripe.com' });
const res = await fetch(`https://api.screenshotneo.com/v1/shot?${q}`);- Before a screenshot, it accepts cookie or consent banners like a visitor and removes more than 60 known consent platforms, newsletter popups, and chat widgets; each step can be turned off.
- Bot checks or CAPTCHAs, blank pages, timeouts, failed loads, and cache hits are not billed. Response headers identify the page verdict and billing status.
- An MCP server provides
take_screenshot,get_page_info, andcapture_pdftools for Claude, Cursor, and other MCP clients. - The free plan includes 1,000 screenshots per month with no card; paid plans start at $5 for 3,000 screenshots.
Sign up for 1,000 free screenshots a month with no card.
Frequently Asked Questions
Can a webpage start recording without me knowing?
No. Screen capture requires the browser to ask you to choose and approve a source; a page cannot silently preselect one.
Special offer. See more information about Outbyte and uninstall instructions. Please review EULA and Privacy policy.
Does a screenshot API record my screen?
No. A screenshot API captures a webpage URL as an image or PDF; it is different from browser display capture, which asks the user to share a screen, tab, or window.
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