【浏览器插件】Screencastify (Screen Video Recorder)
Screencastify is a simple video screen capture software (aka.（亦称） screencast（截屏视频） recorder) for Chrome. It is able to record all screen activity（屏幕活动） inside a tab, including audio（声音）. Just press record and the content of your tab is recorded. So you can easily create a screencast for video tutorials（视频教程）, record presentations（产品介绍） etc. It also supports desktop capturing, allowing you to record anything on your screen (not just（不只是） tabs).
Videos are recorded as webm/vp8 files with Ogg Vorbis audio and can be saved to disk（被保存至磁盘） or uploaded to（上传到） Youtube or Google Drive with a single click.
Screencastify does not depend on any external software (like Java, Flash or other plugins). So it also runs on Chromebooks and Chromeboxes.
Video recording（视频录制） happens completely locally（完全在本地）. So your recordings are not transferred to any remote system（远程系统） unless you choose to upload them. Your video files are stored on a sandboxed local HTML5 file system managed by Chrome. When choose to store your recordings on Google Drive, they are uploaded to your Google Drive account after recording and removed from local storage（本地存储）. This helps to save local storage space（节省本地存储空间）, especially on Chromebooks and allows access your recordings from other devices.
Keyboard shortcuts can be configured（配置） in the Options.
The free version allows to record videos that are 10 minutes long. To record longer videos, it can be upgraded to a paid version（付费版） (see https://www.screencastify.com/buy for details).
Please report any issues you might experience using the integrated bug report tool（集成的bug报告工具）.
About extension permissions（关于扩展许可）:
On installation, you’ll be warned that the permissions Screeencastify requests, allowing it to:
– Access your data on all websites:
This is triggered by the tabCapture API, that Screencastify uses to record tabs. See here (https://goo.gl/hLR4f8) for a discussion（讨论）.
It’s also triggered by the host permission for <all_urls>. This is required to draw the mouse pointer（鼠标指针） inside the tab (via a injected content script) while recording.
– Access your tabs and browsing activity:
Triggered by the webNavigation API that Screeencastify uses to detect navigation and re-draw the mouse pointer on new pages while recording.
Also triggered by the tabs API that is used to detect when a tab becomes inactive（不活跃的）. This way Screencastify can warn you when you’re recording a tab that is not in the foreground any more.
– Capture content of your screen (only on Chrome Beta):
Triggered by the desktopCapture API, this only covers desktop recording (not tab recording) so far and only on the Chrome Beta or Dev channels.
If you want to dive deep, take a look at the official extension API documentation（官方扩展API文档） (https://goo.gl/8eerN5) that explains how API permissions map to（映射至） install-time（安装时） warnings.
Please be aware（知道的） that the warnings are designed to warn you what the extension could do which such permissions, not what it actually（实际上） does (https://goo.gl/14S1q8). Screencastify does not do anything malicious（恶意的）, in fact it does not do anything at all while not in use. It unloads itself to save resources（节省资源） and just waits for clicks on the extension icon or keyboard shortcuts. (Can be verified by activating the developer mode（启动开发者模式） on chrome://extensions and inspecting its view（检查视图） and the absence of its content-scripts on any page while not recording).
Changelog：moved to plus.google.com/+ScreencastifyChrome