Google Native Client (NaCl) is a sandboxing technology for running a subset of Intel x86 or ARM native code using software-based fault isolation. It is proposed for safely running native code from a web browser, allowing web-based applications to run at near-native speeds, which aligns well with Google's plans with Chrome OS. It may also be used for securing browser plugins, and in the future parts of other applications or full applications.

To demonstrate the readiness of the technology, on 9 December 2011, Google announced the availability of several new Chrome-only versions of games known for their rich and processor-intensive graphics, including Bastion. NaCl runs hardware-accelerated 3D graphics (via OpenGL ES 2.0), sandboxed local file storage, dynamic loading, full screen mode, and mouse capture. There are also plans to make NaCl available on handheld devices.

Native Client is an open-source project being developed by Google. To date, Quake, XaoS and MAME have been ported to Google Native Client Platform. Native Client was formerly available as an experimental disabled-by-default feature in the Google Chrome web browser. The feature is enabled from version 14 of Chrome; at the same time, native applications can be uploaded to the Chrome Web Store, and with more recent Chrome versions (if enabled in chrome://flags), native client applications can run under Chrome from any web site. When Portable Native Client (PNaCl) is released, Chrome will enable Native Client (by default) for all pages and web apps, including those distributed outside the Chrome Web Store.