"Viewable" refers to something that can be seen or accessed by someone. It means the object, content, or information is visible or available to be viewed. Full definition
Our responsive legal websites are easily viewable on mobile devices. (lawyermarketing.com)
On the Member Recipe Upload page, you can choose to share your uploaded recipe with other Epicurious users, or make your recipe «private» and not viewable by others. (epicurious.com)
Viewing angles are not IPS, but easily viewable from at least 45 degrees off centre laterally and from the top — only when tilted away from the bottom does it wash out more quickly (though I guess if I had rotated the tablet 180 degrees, it would make it wash out from the top quicker than the bottom). (blog.the-ebook-reader.com)