I'm going to start working on the brand-new web application with Vaadin 14 Flow (pure Java). Right now, I'm unable to find the clear information about - will my Vaadin 14 Flow (pure Java) web application be SEO(Search Engine Optimization) friendly out of the box or no? And if no - what additional steps should I implement in order to achieve this? Also, is it worth to add PWA support to the application and how complex is it in case of Vaadin 14 Flow (pure Java)?
This question is on the fringe of StackOverflow policy, as it is potentially quite wide, so I am just answering briefly on top level. This question is seldomly asked in context of Vaadin applications, as they tend to be mostly implemented for company internal use, and thus SEO is not a requirement. Vaadin stance regarding SEO is neutral. So this is mostly application implementation level question. What you need to know is, that Vaadin's component implementations are web components, thus their internals are protected by shadow DOM. This means, if you have say ComboBox and you have set label to it, the label is not necessarily exposed to search index crawlers. In most cases it is not even necessary. Vaadin's layout components place components in light DOM, so if you use native html components representations like Span, Div, H1, H2, ... for the texts that you want to be exposed to SEO, you will be ok. Your text content will be exposed to the indexing crawlers. The rest is just about proper SEO copywriting, and that is naturally out of scope of Vaadin. You may be also interested in GoogleAnalyticsTracker.