What tech stack do you use for quick web side projects?

This is as "quick" as side projects go: https://crushentropy.com/ (Markdown for hi-res planning). I made it one weekend a couple years ago and I've used it myself ever since.

App served by Flask running on App Engine. Data persisted to Firebase. Costs me approximately $0 per month. 100% uptime afaik.

Flask (Python) for super simple stuff with no db (I have a custom ldap user and groups manager for example) with semantic ui frontend and crude html. Ktor in kotlin for any API thing that needs to last. Spring boot in kotlin for stuff that require auth and db with vue.js in front using type script. (Makes developing one week viable products doable)

Heroku is my go-to for spinning up a quick stack with minimal effort. Their free-tier is pretty powerful. It's mainly for POC-type work so if you're trying to launch something into production, you will most likely need to switch to a paid plan or a different platform / solution.

React + Firebase (auth and DB) + whatever minimal CSS I run across.

None of my personal projects get used much so none of the costs of Firebase really come into play for me.

JavaScript (vanilla or Angular), Bootstrap, GitHub Pages.

rails