Text Editor is a full-featured text & code editor extension for your browser.
This extension has plenty of options to adjust and is built on top of the famous CodeMirror open-source JavaScript library (https://codemirror.net/). Once you open the add-on for the first time, you will see a sidebar at the left and an empty text editor at the right. The left sidebar includes file I/O buttons. For example, a button to open file(s) or settings. There is also a right sidebar which includes all the options for this app.
Note 1: from v0.1.7, this extension supports the new file access API (https://web.dev/file-system-access/) that can read and write files to disk. For older browsers, it uses the chrome.downloads API to save text files to local disk.
Note 2: this extension supports three keymaps for famous text editors (i.e. sublime) and more than 100 coding languages (i.e. JavaScript, CSS, HTML, etc.).
You can install this app as a PWA on your mobile device, moreover, it is available as a browser extension as-well-as a web application:
Chrome: https://chrome.google.com/webstore/detail/text-editor/demheclfdlemkkpadenmajhjbdhbjjml
Edge: https://microsoftedge.microsoft.com/addons/detail/text-editor/plnfalmmnbhnfboannecofbompkgkflf
Firefox: https://addons.mozilla.org/en-US/firefox/addon/text-editor-extension/
Opera: https://addons.opera.com/en/extensions/details/text-editor/
Webapp & PWA: https://webbrowsertools.com/text-editor/
Support & FAQ: https://mybrowseraddon.com/text-editor.html