These SEO tools are worth keeping open, starting with the free reports from Google and Microsoft. Most sites need these before they need anything else.

Technical SEO tools go deep on crawling and indexing.
Microsoft's free reports for Bing, including its AI Performance data.
Google's own free reports on how your site performs in Search.
The desktop crawler for technical SEO audits.
GEO and AI Search tools track how AI answers pick their sources.
Free tools for checking AI visibility, fan-out searches and crawl access.