How JustRecordScreen Works
Your recording is captured entirely in your browser. Here is exactly what happens under the hood.
Browser-Native Recording
JustRecordScreen runs entirely in your web browser. When you record your screen, every step happens on your device — no file is ever sent to any server, and no external service processes your data.
Technical Implementation
The tool is built on these native browser APIs and capabilities:
Screen Capture API (getDisplayMedia)
A browser built-in API that lets a web page request permission to capture your screen, a window, or a browser tab. Your browser handles the permission prompt and streams the captured video frames directly to the page — no plugin or extension required.
MediaRecorder API
A browser built-in API that accepts the video (and audio) stream from the Screen Capture API and encodes it into a WebM file locally on your device. The resulting file is assembled in memory from individual data chunks — nothing is transmitted over the network.
File API (Blob + URL.createObjectURL)
Once recording is complete, the MediaRecorder's output chunks are combined into a Blob object. URL.createObjectURL() creates a temporary local URL pointing to that Blob, which is used for the in-browser preview player and the download link. The file exists only in your browser's memory.
WebM / VP9 + Opus
The output format is WebM, using the VP9 video codec and Opus audio codec. These are native browser codecs — no transcoding library is needed. VP9 provides excellent quality at small file sizes; Opus handles both microphone and system audio efficiently.
What This Means for Your Privacy
- Your recording is never uploaded to any server
- No third party receives or processes your recording
- We have no access to the content of your recordings
- No video data, filenames, or metadata are logged or stored
- Your recording exists only in your browser's memory during the session
How to Verify
You do not have to take our word for it. Here is how to confirm:
- 1 Open your browser's developer tools (press F12, or right-click and choose Inspect)
- 2 Go to the Network tab
- 3 Use the tool to record your screen
- 4 Observe: no outbound requests contain your recording data
Alternatively, disconnect from the internet after the page loads. The tool continues to work — because it requires no server. Recording, preview, and download all work offline.
Trade-offs and Limitations
Because recording is assembled in your browser's memory, very long recordings or high-resolution captures may approach your device's RAM limit — especially on lower-end machines. The output format is WebM (not MP4), which is natively supported in all major desktop browsers. If you need an MP4, you can convert the downloaded WebM file using a local tool.