I know this question is fairly old, but I reached it by looking for a tool with those specific requirements.
I ended up at this web implementation: https://iguana.alerque.com/slappasswd.html
There is no storage or transmission of the password, the hashing is done completely offline (...
Personally, I quite like Haroopad. It is pretty simple, but also pretty quick. It updates visualization as I go and synchronizes scrolling source -> view. Which is pretty much what I need.
I mainly use other softwares on linux for my markdowns, but when I need to edit them in windows I use ghostwriter. It may lack some advanced features (e.g. external themes/fonts support), but it is a great editor.
Below you can see an example of the live HTML preview
I like using one program for everything. I use SublimeText, which is free for evaluation just like WinRar, for almost any text editing purposes and there's almost always a plugin for a certain type of file. The plugins are also mostly open source so you can edit them to your liking.
After re-reading the question, I've found what I used to use for this ...
CuteMarkEd is a free and open source markdown editor. It fits all listed requirements:
Simple and lightweight: Download the zip file extract and finished (no Installation required, Zip file is currently 37 MByte)
It's open source (Github)
You can view the formatted content.
I would recommend Atom editor. You will need to install Markdown Preview but a big advantage is that there is large amount of additional plugins for handling markdown. The preview is opened via Ctrl + Shift + M.
Atom is available for Windows, Mac and Linux.
If you work a lot with Notepad++ (GPLv2), you can install the MarkdownViewerPlusPlus plugin (MIT License):
(According to the Github page, this plugin works for 32 and 64 bits)
Alternativelly, you can use the NppMarkdownPanel plugin (MIT License):
(According to the Github page, this plugin also works for 32 and 64 bits)
Both options can be installed from ...
I use Typora free (commercial license, not open source) software for Windows/Mac/Linux because it works very fast. The latest version of Typora is currently a beta version and it's free software, but Typora may cost something in the future.
Typora can capture rich content directly from word processors and webpages, convert it directly into markdown text via ...
Its not really simple and lightweight, but
You can use Visual Studio Code, it has a Markdown preview built-in. This way you can view the source and the rendered preview side-by-side.
To display images in-line (at this time) you need to install an extension, Markdown Preview Enhanced by Yiyi Wang.
"Markdown Preview Enhanced is an extension that provides ...
JShell — a REPL now bundled with Java
You may find useful the REPL tool now bundled with Java 9 and later, JShell, defined in JEP 222.
Use a search-engine to find many demonstrations, both written and video.