One of the simplest ways to turn a simple web project into a PWA. By simple web projects I mean plain HTML/CSS/JavaScript with no bundlers or build tools. Something you would build on Glitch.

Add a service worker so your app works offline.

• 🔖 Jeremy Keith (2018). “Minimal viable service worker”

Add a web manifest.

• 🔖 tomitm, “Web App Manifest Generator”

Installability criteria: https://web.dev/install-criteria/

As of 2020-12-14

• HTTPS
• Web App Manifest must contain 192px and 512px icons
• Service worker must return a valid response when the device is offline