Choosing a WordPress theme and choosing your navigation plugin should be decisions made together, not sequentially. A theme that makes certain assumptions about how navigation works can make a third-party menu plugin much harder to implement — sometimes impossible without custom CSS.
Here’s what to look for.
A clean, accessible header region
The header is where navigation lives, and some themes treat it as a tightly controlled component. They position the header with fixed dimensions, apply overflow constraints that clip dropdown panels, or build the navigation into a mega component that’s difficult to replace.
Before committing to a theme, check whether there’s a standard WordPress menu location registered for the primary navigation. If the theme uses a custom header builder that bypasses the menu API, adding a standalone plugin is going to require workarounds.
Minimal interference with link styles
Themes often define global link styles — color, font size, font weight, text decoration — that cascade into every a tag on the page, including your menu links. A well-built navigation plugin will scope its link styles inside its own wrapper, but a theme with very aggressive global styles can still interfere.
Look at a theme’s stylesheet before committing. If it sets link styles without scoping them, expect to write some override CSS.
Z-index sanity
Dropdown menus need to appear above other page elements. Themes that define z-index values for their header, sticky navigation, or hero sections can interfere with this. A plugin that manages its own z-index carefully — rather than just setting everything to 9999 — is better equipped to handle this, but the theme still needs to cooperate.
Reasonable overflow behavior
overflow: hidden on the header element is the most common reason dropdown menus get clipped. It’s a surprisingly common theme pattern — used for visual tidiness — and it invisibly breaks any dropdown that extends below the header boundary.
Test any theme you’re evaluating by installing your navigation plugin and checking that dropdowns appear correctly. This is a five-minute test that can save you hours of debugging.
FSE themes and block themes
Full Site Editor themes introduce additional considerations. Navigation added via a Custom HTML block in the Site Editor bypasses many of the traditional header concerns, but introduces new ones around z-index stacking contexts and global style bleed-in from wp-site-blocks. These are solvable, but they’re worth knowing about.
Ruby Mega Menu handles FSE compatibility explicitly, including z-index stacking context fixes via :has(#ruby-mega-menu) selectors and protection against global style interference.
The short version: choose a theme that registers a standard menu location, has reasonably scoped global styles, and doesn’t apply overflow: hidden to the header. Most well-maintained themes fit this description. When in doubt, test before committing.