Joplin Copy as HTML Plugin 
NOTE:
My coding knowledge is currently very limited. This plugin was created entirely with AI tools, and I may be limited in my ability to fix any issues.
I mainly created this plugin for myself, but I figured others may find it useful:
This plugin allows you to copy selected text in the markdown editor as either HTML or plain text (with markdown formatting characters removed).
The primary use case is copying text from Joplin and pasting formatted text into other apps that support HTML formatting (e.g. pasting text into an Outlook email). A plain text fallback is provided for scenarios where you need to paste text into an application that supports neither HTML formatting nor markdown.
Copy as HTML
"Copy selection as HTML" is provided as a right click context menu option and as a keyboard shortcut (ctrl + shift + c by default).
This will populate the clipboard's text/html category with the HTML formatted text.
Embed images as base64
By default, the plugin will embed any images as base64 in the text/html output, allowing you paste text + images into external applications. However, this can be disabled in the plugin's settings.
This should work with both markdown image embeds and the html <img> embeds that you get when resizing images via joplin's rich text editor.
Export as fragment or full HTML document
When you copy text from Joplin's markdown viewer (or export the note to HTML), there is a lot of styling applied which can sometimes cause issues pasting text into other editors (e.g. if you copy from the markdown viewer, your joplin theme's background color may be pasted).
HTML Fragment
By default, the plugin will populate the clipboard with an HTML fragment, e.g:
<html>
<body>
<!--StartFragment-->
<h2>Test Heading</h2>
<p>Test paragraph 1</p>
<p>Test paragraph 2</p>
<!--EndFragment-->
</body>
</html>
This is similar to what you get when copying from Joplin's TinyMCE rich text editor (semantic markup, no css styling). Any styling will be determined by the application you're pasting the text into.
Full HTML Document
Optionally, you can enable the setting "Export as full HTML document".
This will wrap the HTML fragment in a full HTML document with CSS styling. A default (minimal) css stylesheet is provided. The default stylesheet is only used if no custom stylesheet is provided and the "Export as full HTML document" setting is enabled.
To use your own stylesheet, create a file called copy-as-html-user.css in your Joplin profile directory. To locate your Joplin profile directory, open Joplin and click Help | Open profile directory.
Optional markdown syntax
The plugin will adhere to Joplin's settings for whether or not to render:
- Soft Breaks
- Typographer
- Linkify
- ==mark==
- Footnotes
- Table of Contents
- ~sub~
- ^sup^
- Deflist
- Abbreviation
- Markdown Emoji
- ++Insert++
- Multimarkdown Table
Copy as Plain Text
"Copy selection as Plain Text" is provided as a right click context menu option and as a keyboard shortcut (ctrl + alt + c by default).
This will strip markdown formatting characters, backslash escapes, and image embeds from the source markdown and populate it as text/plain in the clipboard, for scenarios where you need to paste into an app that supports neither HTML formatting or markdown.
List leaders and nested list indentation will be maintained (these are normally lost when copying from the markdown viewer or rich text editor).
Customizing plain text output
The following options are provided to preserve specific markdown formatting in the text/plain output:
-
Preserve superscript characters
(^TEST^) -
Preserve subscript characters
(~TEST~) -
Preserve emphasis characters
(*TEST* or _TEST_) -
Preserve bold characters
(**TEST** or __TEST__) -
Preserve heading characters
(## TEST) -
Preserve strikethrough characters (
~~TEST~~) -
Preserve horizontal rule (
---) -
Preserve highlight characters
(==TEST==) -
Preserve insert characters
(++TEST++)
The following options are provided for external hyperlinks (only impacts markdown links containing http/https URL):
-
Title - Displays link title only (default).
-
URL - Displays link URL only.
-
Markdown Format - Displays full markdown link formatting with title and URL.
Markdown emoji
Copy as Plain Text supports the markdown-it emoji plugin, so emoji such as 
will be displayed in the plain text output. This can be disabled if desired via the Display emojis setting.
Known Issues
- The context menu options appear in the rich text editor's context menu (but aren't functional, the plugin is only intended for the markdown editor).
- The plugin's keyboard shortcuts sometimes don't work on cold start of Joplin, can be fixed by toggling editors or going to Tools | Options | Keyboard Shortcuts and back.
- When using the "Full Document" mode for custom css styling, the full HTML document will be nested under another
<html>/<body>in the clipboard. I don't think there's a way to fix this without having access to electron clipboard API. Nested html/body (while not technically valid HTML) is the best solution I found (doesn't seem to cause issues pasting into other apps and is the same thing that the obsidian copy document as html plugin does).
