Great add-on! Thanks very much to the developer for this. 🙏

I use it every day. Works great, also with Neovim.

This plugins works perfectly. An external editor for web form has saved my nerves many times after editing a long text for hours and, for some reasons, the browser crashes or I inadvertently press the cancel button instead of submit, etc. So I was very happy to see withExEditor doing the job, after years of using late-ItSAllText (who passed away with firefox 57 webextensions). Note that the host is to be downloaded from https://github.com/asamuzaK/withExEditorHost while the home page points on /https://github.com/asamuzaK/withExEditor

emacsがないと生きていけないので、ほんとうにありがた使わせていただいています。。。!

Textern was not working for me (it was getting errors writing to the tmp file) so I gave withExEditor a try.
So far withExEditor has been working quite well.

Great for editing textareas in Vim, on the press of a keystroke (I use Ctrl+E).

A suitable replacement for other extensions that have provided this over the years (It's All Text!, ViewSourceWIth, and MozEx).

The separate host software (made necessary by WebExtensions) was straightforward to install. The default keystroke is Ctrl+Shift+U, which for me (on Ubuntu Linux) is used by the desktop environment for entering Unicode characters.

You can trigger per-website editor customizations on the path of the file being edited: the temporary file's parent directory name is the site's domain name.

It works really well. I mostly use it to compose emails, but sometimes for viewing page source, etc. Setup of the host is much improved over earlier versions.

There is good and bad news here. The good news first:

GOOD:
If you take the time to set it up, it works great. I would suggest a few minor modifications to make it nearly perfect.

1) When you close the file your editing, the edited text in the browser should "light up" like it does with "Its all text".
Note: The reason that "withExEditor" appeared was to replace "Its all text" which was a Firefox plugin that was rendered "out of date" due to Firefox (Mozilla) security issues with plugins and extensions. (Did I get this reason right?).

2) The "documentation" (see below for the bad news) says that you "right click" to start the process of transfering the text to be edited to your local editor (notepad, gvim (vi), emacs, gedit, what ever). However this very important instruction is not properly defined. I searched the internet high and low to try to understand what to "right click" on.
Eventually by hours of trial and error, I discovered that the key-stroke required was a double-right-click of the mouse button in the text area that was to be edited. Once this was done (two right mouse clicks, pointed at the right region), the menu came up, and at the bottom of the list was a "withExEditor" icon. when I selected that, then the text was transfered to my editor (gvim in my case).
Conclusion: The documentation needs to explain exactly how withExEditor is to be started. The present documentation is on the verge of non-existant on almost all points (see below on the bad).

3) So far I have not been successful in getting the "u" option to work. From a review it seems that one should try "ctrl-shift-u" I have not yet tried that.
NOTE: withExEdit does not work on this review!!! I can see the line for withExEditor if I right click, but its grayed out. OMG.

BAD:
I don't know where to start there are so many problems. It took be 8 hours of work to get this installed, mostly because of the very poor (almost nonexistant) documentation. First, if your not a GitHub user, you need to educate yourself a bit. You don't need an account, but you had better learn how to use the basics, like downloading a zip file and unzipping it, and following the instructions.
2) Most important of all is that you will need to have node version 8.X installed. So how do you know what version of node you have? Simple (I guess its simple): From the command line (xterm) run the command
node -v
If it doesn't come back at all, you don't have node installed. Try "man node" to find out more. Ubuntu 16.04 comes with node 4.x installed. I purged this (sudo apt purge node) and then found the latest version (8.9.3) and installed it from a tar file (https://nodejs.org/en/download/).
3) Then the "docs" keep talking about a "Host" but nowhere is this defined (at least to my satisfaction). For this you need to download the host.js package from the author's github site (https://github.com/asamuzaK/). Here you will find a zip for both the app and the host. You need to install both.
4) Once the host is installed you need to configure it, which is done with the command "node setup.js" as described in the README.md file in the host package download. If you get an error with this command, it likely means you have an old version of "node."

In summary, the software is great, the documentation is a nightmare. It left me feeling like I was stupid. But I really needed this function (for reasons I wont go into), so I kept plugging away with some faint hope that it would work once I figured it all out. I have been using Unix/linux for 15 years, and it took all that experience to get through this. I have no idea what a windows user will experience, but likely many of the same problems.

So I love it, and it almost works perfectly, but the install process almost killed me. Now I'm using this daily, and I cant live without it. For example: If you editing a wiki and you want to copy the entire script, then click it to your editor, and save the file. Then edit locally, and ship it back, and OMG that is so much better. Wiki editors are horrible. Same with email editors (e.g., Firefox). I want to know if this can work with Firefox so I can edit my email using gvim. What a relief that would be.
How about it, asamuzaK, is that possible?

Thanks for your hard work. Maybe better docs next time? Don't assume genius users next time.