Chrome does not support Unity3d Webplayer plugins from the V39 version by default

To enable it, you need to manually enter the following command in the Chrome browser to open
chrome://flags/#enable-npapi

Cite an article from Chrome's official blog to explain why Chrome is not compatible with the Unity3d Webplayer plugin by default:

The Final countdown for NPAPI

Posted:monday, November 24, 2014

Last September we announced our plan to remove NPAPI support from Chrome, a change that would improve Chrome's security, SP Eed, and stability as well as reduce complexity in the code base. Since our last update, the NPAPI usage has the continued its decline. Given This usage data, we'll continue with our deprecation plan.

Monthly Plug-in Launch Percentage

Currently Chrome supports NPAPI plugins, but they is blocked by default unless the user chooses to allow them for specifi C sites (via the page action UI). A small number of the most popular plugins is whitelisted and allowed by default. In January we'll remove the whitelist, meaning all plugins would be blocked by default.

In April NPAPI support would be disabled by default in Chrome and we'll unpublish extensions requiring NPAPI plugins From the Chrome Web Store. Although plugin vendors is working hard-to-move to alternate technologies, a small number of users still rely on plugins That haven ' t completed the transition yet. We'll provide an override for advanced users (via chrome://flags/#enable-npapi) and enterprises (via Enterprise Policy) To temporarily re-enable NPAPI and they wait for mission-critical plugins to make the transition.

In September we'll remove the override and NPAPI support is permanently removed from Chrome. Installed extensions that require NPAPI plugins would no longer be able to load those plugins.

For more details on the timeline, including guidance for NPAPI plugin developers, see the NPAPI deprecation Guide. With each step of this transition, we get the closer to a safer, and more mobile-friendly the Web.

Chrome does not support Unity3d Webplayer plugins from the V39 version by default