It has been announced some time ago and was in private preview since then.

imageNow you can request to sign up to Visio Online for Office 365 at https://microsoft.qualtrics.com/jfe/form/SV_emHCbdUAEQs18Kp

Once your tenant is enabled for Vision Online you will be able to create,edit and view Visio files using your web browser as you can already do with other Office documents.

At this stage, Vision Online is only available in English, German, Spanish and French.

Enjoy