Requests go directly from your browser to NCBI's E-utilities API. dash-seqviz does not operate a proxy: your email is sent to NCBI with each request, as their usage policy recommends, so they can reach you if your usage causes issues.
Your email is stored locally in your browser only (localStorage). We cap you at 3 requests per second (NCBI's unauthenticated limit), cache responses so repeat accessions don't re-hit NCBI, and refuse obviously invalid accession strings.
For heavy or automated use, please get an NCBI API key and run your own workload, not through this public demo.