I often write code on the go (for e.g. on bus rides), mainly prototyping ideas as single-page HTML/CSS/JS. I’ve used code editor apps as well as developer keyboards on mobile phones, but none of them really clicked for me. So I built something for myself: a simple browser-based code editor, optimized specifically for mobile devices. It lives at https://me.cmdr2.org/carbon (GitHub repo), runs entirely in the browser, and stores your work locally.
The editor currently supports only single-file HTML/CSS/JS projects. It’s meant for quick prototyping, not large-scale work, and does not require installation. But if you want, you can install it as a PWA.
One of the main pain points I wanted to solve was the mobile keyboard experience. Switching between keyboard pages just to access symbols was slowing me down. Using touch to position the cursor often resulted in it landing a few characters to the left or right of where I actually needed it. And you can’t really indent or unindent using the regular mobile keyboard that I need for normal use. So I added a floating keyboard overlay with essential programming keys—tab/shift-tab, arrow keys, braces, etc.
This project also gave me the excuse I needed to explore web components more deeply. The first version was just a plain HTML/JS single-page app. Then I rewrote it using custom web components from scratch—no frameworks, just the spec. Finally, I migrated it to use Lit and Shoelace to simplify the UI while retaining the same component architecture.
This isn’t meant to be a full IDE or to compete with existing tools—it’s just a lightweight scratchpad that’s fast and designed around real-world constraints of mobile coding. It’s mainly meant for me, but others are free to use it as well if they find it useful.