
Google Chrome remembers and always load some websites with custom zoom levels set by the users — you can check for which sites you’ve set particular zoom level by hitting ‘Manage’ button under ‘Zoom levels’ in ‘Content Settings’ — which used to be the case with Vivaldi till 1.3 version, but this has changed now with Vivaldi 1.4.
READ: How to reset Websites Zoom Level to Default in Firefox browser
Make Vivaldi to remember site specific zoom level in version 1.4
Vivaldi team has enabled tab specific zoom -which lets you set zoom level for each tab rather than for each site – by default. And the default zoom for a webpage has been set as 100%. In Vivaldi 1.4, if you’ve viewed webpage by setting to a zoom level, when you close and visit the same webpage, its zoom level will be defaulted to 100%.
Yes! Use Tab Zoom option, which has been kept disabled since Vivaldi 1.0 has been turned on by default.
This has confused users as their site specific zoom will be no longer be saved or preserved and maintained across sessions. Solution is simple, visit Settings > Webpages and uncheck Use Tab Zoom.

my goodness! thank you so much! This was driving me crazy. Vivaldi team should provide better description for what tab zoom does.