An SEO audit should include:
Common issues (meta title, meta description, and Google search results preview)
Competitor domain analysis
Keywords test (keywords cloud, common keywords and whether they’re being used in your titles, and related keywords)
Backlinks test
Sitemap test
Speed optimizations
Server and security checks (HTTPS and URL canonicalization)
Mobile usability
Advanced SEO (nofollow tags, custom 404 error page, and structured data)