Side panel extensions
Rio runs Chrome's side panel extensions. They open on the right, next to the page, as they do in Chrome, so a dictionary or an assistant stays beside what you are reading. Arc does not support side panels. Rio is free and open source, and it installs them from the Chrome Web Store.
Look something up without leaving the page
You are reading the Hudson River article on Wikipedia and hit the word estuary. Open your dictionary extension and its side panel slides in on the right with the Wiktionary entry: pronunciation, etymology, the Latin it comes from. The article stays on the left. Close the panel when you are done.
The same goes for any extension built for Chrome's side panel, such as an AI assistant or a notes tool. They get a full-height panel next to the page instead of a small popup that closes when you click away.
Who supports side panel extensions
| Browser | Side panel extensions |
|---|---|
| Rio | Yes, on the right next to the page |
| Chrome | Yes, since Chrome 114 |
| Dia | Yes, since Dia 1.10.1 (December 2025) |
| Arc | No |
| Safari | No, Safari extensions use their own model |
If you used Arc, this is one of the things it could not do. Page Assist, an extension that runs local AI models in a side panel, lists Arc's sidebar as not supported in its own README.
Installing one
Install the extension from the Chrome Web Store as you would in Chrome. Its side panel opens on the right. If you are moving from Arc, Rio's import lists the extensions you had there so you can reinstall each with one click. See Move from Arc to Rio.
Questions
What is a side panel extension?
An extension built on Chrome's sidePanel API, available since Chrome 114, that shows its own page in a panel beside the website you are on instead of in a popup.
Does Arc support side panel extensions?
No. Page Assist's README lists Arc's sidebar as not supported, and Dust's help forum says Arc doesn't currently support side panels. Rio, Chrome and Dia do.
Where do I get side panel extensions for Rio?
From the Chrome Web Store, like any other Chrome extension. Rio runs Chromium 158 and installs Manifest V3 extensions.
Does Safari support them?
No. Safari extensions come from the App Store and use their own model, without Chrome's sidePanel API.
Sources
- Chrome for Developers, chrome.sidePanel (Chrome 114 and later)
- Page Assist README, Browser Support (Arc: sidebar not supported)
- Dust community, Arc doesn't currently support side panels (May 2, 2025)
- Dia changelog 1.10.1: side panel extensions render in Dia (December 18, 2025)
- MDN browser-compat-data, sidePanel (Safari: not supported)
- Safari User Guide, Get extensions
