Can I customize the HTML, CSS, and JS for UI5 / Fiori?

Question

Is it possible to add CSS classes and add or edit the JavaScript to make things look and feel different without colliding with SAPUI5 support or releases? Regarding micro animations, loading behavior, change of boarders, fonts, and adding an hover state, etc.

I want to get a realistic and reliable understanding of what is possible, without breaking the responsiveness or adding an unrealistic amount of work to things.

Answer 1

UI5 application developers are allowed to:

• Use only public APIs visible in API Reference.

• Only if you're extending a public module, you may additionally incorporate protected APIs to your UI5 control customization. Sample: https://stackoverflow.com/a/67919830/5846045

• For SAPUI5 apps on SAP Fiori launchpad: do not manipulate directly the HTML and CSS output rendered by the UI5 framework.

  As stated in the Compatibility Rules, the HTML and CSS generated by SAPUI5 is not part of the public API and may change in patch and minor releases. [...] As such, SAP Fiori launchpad apps should not override styles. (Source: "Custom CSS and Theme Colors")

See Compatibility Rules and Use Only Public APIs for more information.