I always ask to see their personal website, showing me sites of client accounts they’ve worked on does not impress me, but a personal website does. I consider this the equivalent of an SEO or web developer resume. There are certifications from Hubspot and SEMRUSH you can take, but certifications mean very little since it’s easy to cheat/hack these answers online as well.

Having a strong web developer background, content writing background will go a long way, and help give you a competitive advantage over others.