Engineering service
Opera add-ons and Opera-style browsers
Opera's code is proprietary, so nobody outside Opera can fork it. We help in four ways: Opera add-ons and sidebar extensions, your Chrome extension listed and tested for Opera, Opera GX mods, or Opera-style features in a Chromium browser you own.
- 11+ years of experience
- 300+ projects delivered
- Remote team, clients worldwide
- NDA on request
Overview
What it is and when it fits
Opera and Opera GX are built on Chromium, but Opera's own code is proprietary, so nobody outside Opera can fork or patch it. What Opera does offer is a way in through extensions: it runs Chromium extensions, adds its own sidebar extension API, and lists add-ons in its own catalog at addons.opera.com. Opera GX also accepts mods that change how the browser looks and sounds.
That leaves four routes: an Opera add-on or sidebar extension, your existing Chrome extension tested and listed for Opera, a GX mod, or your own Chromium-based browser with Opera-style features. If you want to reach people who already use Opera, pick one of the first three. If you want your own product with that kind of interface, pick the browser.
Who this is for
- Teams that want to reach Opera and Opera GX users with an add-on or a sidebar extension.
- Extension developers who want their Chrome extension listed on addons.opera.com and tested in Opera.
- Game and creator brands that want an Opera GX mod: themes, wallpapers, sounds and page styles.
- Companies that want Opera-style features, such as a sidebar or workspaces, in a browser of their own.
How it works
Architecture at a glance
Route 4: Opera-style features in your own browser
Opera-style features in your browser
A sidebar with web panels, workspaces, built-in tools and a layout designed for your product.
Feature modules
Each feature built as a separate module with a small footprint in Chromium code, so upgrades stay manageable.
Chromium
Blink, V8, Content, networking and the sandbox. None of Opera's own code is used.
Build and release
- Windows
- macOS
- Linux
CI, installers, code signing and auto-update for the platforms you ship.
- Your productWhat your users see
- Our engineeringWhat we build and maintain
- UpstreamThird-party code we build on
- Platforms and releaseBuild, sign and deliver
What we offer
What we build for Opera users
Opera add-ons
Extensions built for Opera and published on addons.opera.com, prepared for Opera's manual review, which requires readable, unminified code or a link to the source.
Sidebar extensions
Panels that live in Opera's sidebar, built with the sidebar_action manifest key and the opr.sidebarAction API, with Chrome's side panel as the fallback.
Chrome extensions on Opera
Your Chrome Web Store extension tested in Opera and Opera GX, fixed where Opera behaves differently, and listed in Opera's own catalog.
Opera GX mods
Themes, wallpapers, browser sounds, background music, shaders and page styles packaged as a GX mod for GX.store.
Opera-style features in your own browser
A sidebar with web panels, workspaces and tab grouping built into your own Chromium browser, modeled on the interaction, not on Opera's code.
Built-in VPN, ad blocking and resource limits
For your own browser: a third-party VPN SDK or proxy, our own ad-blocking layer, and gaming-oriented CPU, RAM and network limiters, built on Chromium.
Deliverables
What you get
- 01
Route recommendation
A short written answer on which of the four routes fits your goal, and why the others do not.
- 02
Opera add-on or sidebar extension
A packaged extension for addons.opera.com. Sidebar panels use Opera's sidebar_action manifest key and opr.sidebarAction API, with a fallback for Chrome.
- 03
Listing and review support
Readable, unminified source (or a source link with build steps, as Opera's acceptance criteria require), listing text and answers to moderator feedback.
- 04
Opera compatibility pass
Your Chrome extension tested in Opera and Opera GX, with fixes for Opera-specific behavior and a record of the versions covered.
- 05
Opera GX mod
A mod package with its manifest, theme, wallpaper, sounds, shaders or page styles, ready to upload to GX.store.
- 06
Custom browser with feature modules
A Chromium-based browser with the Opera-style features you select, if you choose the fourth route.
Compare
Which route fits
The routes differ in who owns the browser and how much there is to maintain.
| Route | Result | Effort | Choose it when |
|---|---|---|---|
| Opera add-on or sidebar extension | A feature Opera users install from addons.opera.com, optionally living in Opera's sidebar | Low | You want to reach existing Opera users with a specific feature. |
| Chrome extension listed for Opera | One extension codebase for Chrome, Opera and other Chromium browsers | Low | You already have or plan a Chrome extension and want Opera users covered. |
| Opera GX mod | Themes, wallpapers, sounds, music, shaders and page styles for Opera GX | Low | You want your brand or game inside Opera GX. Mods change look and sound, not features. |
| Your own Chromium-based browser | A separately branded browser you control | High | You want a browser product with a sidebar, workspaces or built-in tools that you own. |
Why it matters
What this gives you
Found where Opera users look
A listing on addons.opera.com puts your extension in Opera's own catalog without a second codebase.
One extension codebase for several browsers
An extension built and tested for Opera generally keeps working in Chrome, Edge and other Chromium-based browsers with the same code.
A panel that stays open
A sidebar extension stays next to the page while the user browses, which suits chat, notes, wallets and dashboards better than a popup.
Your own browser when you need full control
If an extension cannot reach what you need, the alternative is a Chromium-based browser you own outright.
Our approach
How an Opera project runs
Pick the route
We clarify your goal and choose between an add-on, a listed Chrome extension, a GX mod or your own browser.
You get: A route recommendation
Build
We build the add-on, sidebar panel, extension fixes, mod package or the browser feature modules.
You get: A working build for your targets
Test on Opera
We test in Opera and Opera GX against Opera's acceptance criteria, or across your own browser's platforms for the fourth route.
You get: Test results and fixes
Submit or ship
We submit to addons.opera.com or GX.store and handle moderator feedback, or ship signed installers for your browser.
You get: A live listing or a release pipeline
When this is not the right fit
- You want to change Opera itself. Its code is proprietary, so nobody outside Opera can patch it.
- You want Opera's built-in VPN, ad blocker or AI in your own product. Those are Opera's services; we build your own equivalents instead.
Tech stack
Technologies we use
The APIs and tools we use for Opera add-ons and Opera-style browsers.
ChromiumOpera Add-ons Catalogopr.sidebarActionChrome extension APIsManifest V3GX mods
JavaScript
C++FAQ
Common questions
No. Opera's own code is proprietary, so it cannot be forked or patched. You can reach Opera users with add-ons, sidebar extensions and GX mods, or build your own Chromium-based browser with similar features.
Usually, because Opera runs Chromium extensions, and Opera users can install many extensions from the Chrome Web Store. A listing on addons.opera.com makes yours easy to find in Opera's own catalog. Opera moderators review each submission and require readable code: no obfuscated or minified scripts apart from third-party libraries, or a link to your source with build steps.
Opera adds a sidebar_action manifest key and an opr.sidebarAction API that place your extension's panel in Opera's sidebar, where it stays open while the user browses. Other Chromium browsers ignore these, so we keep a popup or Chrome's side panel as the fallback in the same codebase.
A GX mod is a package of assets and CSS: themes, wallpapers, browser and keyboard sounds, background music, shaders and page styles for websites. It changes how Opera GX looks and sounds but does not add features. If you need logic, you need an extension.
In your own Chromium-based browser, yes: we build them as separate modules you own. For Opera users, a wallet or tool can only arrive as an extension, like any other Web3 extension.
Start with an add-on or extension unless you need control that extensions cannot give. A browser is a larger commitment because you maintain it against upstream Chromium releases, which Chrome now ships every two weeks.
Related reading
Our services
Related services
Opera
Tell us what you need on Opera
We will tell you which route fits, what Opera's review expects and what a Chromium-based alternative would take.
