Flems is a playground for web development. It's ideal for prototyping ideas & sharing working front-end code examples.
- - flems.io is the most popular Self-Hosted alternative to CodePen.
Codiad is an open source, web-based, cloud IDE and code editor with minimal footprint and requirementsDiscontinued
"Given its age and number of viable alternatives now available, Codiad is no longer under active maintenance by core contributors."https://github.com/Codiad/Codiad/commit/19c9223d70ca0eb164b6891b6e1350c75a62e8f2
shelf.gg is an open source pastebin that makes it easy to find and share lists of resources.
- - shelf.gg is the most popular iPhone & iPad alternative to CodePen.
Publish HTML quickly with open source web editor, HTMLhouse. Use the editor / real-time preview to build your HTML page, and press publish when you're done. That's it! No sign up, no fuss.Discontinued
The last release is from March 2018, and the website and Chrome extension are unavailable.
Atheos is a web-based IDE framework with a small footprint and minimal requirements, built on top of Codiad by FluidByte and the Codiad Team.
Atheos IDE Features
https://pastes.io is a simple and efficient pastebin for mainly code to be distributed neatly and efficiently across the web. It is a website where you can store any text code or snippets online for easy sharing.
HashBin is a paste bin that never sees the contents of its pastes. It should be immune to takedown notices.
Last updated in 2015, although the latest version works without any problem.
Slingcode is a personal computing platform in a single html file. You can make, run, and share web apps with it. You don't need any complicated tools to use it, just a web browser. You don't need a server, hosting, or an SSL certificate to run the web apps.