Use HoLaTeX with the fabulous latex syntax to generate Math formula, TikZ, CircuiTikZ or PGFPlots graphics.
HoLaTeX is a javascript application that runs on the local browser. All tex language to svg image is handled entirely locally, without any call for web services. Thus, all your data remains local on your computer.
HoLaTeX is built with a preloaded package list, as a dynamic payload would be too complex to implement and too long to run.
No, HoLaTeX can not generate PDF, the output is limited to SVG and PNG only. Please use a complet distribution like TexLive for full latex features.