The browser version of Dragon Quest X will receive a Japanese open beta on February 5.
The test is meant to help the dev team sort out any final optimizations and tweaks ahead of the launch later this year. If you’re hoping to test it out, it looks like you just need a browser with HTML5 support, which is pretty much ubiquitous nowadays, along with a Square Enix account.
The browser version is actually streamed from the cloud by Ubitus. If you play Dragon Quest X, cross-saves will be enabled between that version and the browser version. The start time for the test is at 12p JST until February 25 at 11:59p JST.