HTTPS certificate errors in development -- self-signed and localhost

Browser shows certificate errors when accessing local dev HTTPS services. Some features require HTTPS in development.

Use mkcert: brew install mkcert && mkcert -install && mkcert localhost. Alternative: Next.js --experimental-https, Vite @vitejs/plugin-basic-ssl. Never disable cert checking in production.

Browsers do not trust self-signed certs. mkcert creates a local CA that your system trusts.