Definition
Even though both a WW (Web Worker) and a SW (Service Worker) run in an independent thread, and they both share API such as postMessage to talk to the main execution thread, the two technologies have different goals:
| Feature | Web worker | Service worker |
|---|---|---|
| Goal | Heavy computation on the background | Intercept and handle network requests, caching mechanisms, push notifications |
| Access to DOM (document object model) | No | No |
| Persistent | No, they stop working as soon as the browser is closed, but potentially they are active the whole time | Yes, it can be enabled even offline, even with the browser closed, but they can be paused by the browser if not in use |
| Can handle cache | No | Yes |
| Handle push notification | No | Yes |
| Can work offline | Yes, but only if: - the workers’s script has been downloaded - the workers’s logic does not involve web resources | Yes |
| Intercept network requests | No | Yes |
| Communication with the main thread | postMessage API | postMessage API |
| Most used for | Data processing, cryptography, AI | Offline behaviors, used in PWA (progressive web application), caching, push notification |
| Web workers are mostly used to execute complex operations without blocking the user interface |
Service workers are mostly used to handle network requests, caching mechanisms or support offline functionalities