When it makes sense
Use an online teleprompter when you need to record quickly, without setting up an app, account or sync. Open the page, paste the text and adjust the speed.
Basic precautions
Do a short test, place the camera near the screen and avoid very long text blocks. The script needs to sound like speech, not a document read aloud.
Privacy
The text stays in the browser. Even so, avoid pasting sensitive information into any tool if you do not need it for the recording.