Overview

Important update

On August 12, 2011, Google finally removed the Google+ server-side browser sniffing for Opera! Because the Google+ server-side browser sniffing is now gone and because the extensions and workarounds are now unnecessary, you can uninstall the extension or remove the user JS and then reset your user agent back to Opera. Right click > Edit Site Preferences... > Network > Browser identification: Identify as Opera > OK.

Google+ User Agent Enforcer

Forces the Opera user agent so that Google+'s JavaScript will properly detect Opera, even when spoofing the "User-Agent" HTTP header.

How it works:

• When you spoof the "User-Agent" HTTP header, you will bypass Google's server-side browser sniffing, so Google's server will send the complete webpage source code, including the HTML, CSS, and JavaScript necessary for the Google+ web toolbar features, like the notification button and share button, to display.
• Next, when you click on either the notification button or share button in the Google+ web toolbar, Google's JavaScript checks the browser user agent.
  • If you do not have Google+ User Agent Enforcer installed, you will receive an unsupported browser error message because Google's JavaScript deems the spoofed user agent string to be unacceptable.
  • When you have Google+ User Agent Enforcer installed, JavaScript requests for the user agent will always return an Opera user agent string, even when your spoofed user agent is different. This is good because Google's JavaScript now knows that you are actually using Opera instead of wrongly assuming the spoofed browser. If Google's JavaScript wrongly assumes a non-Opera browser, then Google's JavaScript may try to execute non-Opera-specific code -- for example, code that only works in Firefox or Chrome -- which will not work in Opera.

Pros:

• Considerably future proof. You will receive the latest Google code changes when you spoof the "User-Agent" HTTP header.

Cons:

• Less prominently displays Opera user agent. Google may undercount Opera's browser stats.

Google+ Injector

Injects the missing HTML, CSS, and JavaScript code into Google+, which will show the web toolbar buttons and may, by the addition of more JavaScript, increase usability or the number of features.

How it works:

• Because Google performs server-side browser sniffing, Google's server sends Opera an incomplete or crippled webpage, missing HTML, CSS, and JavaScript, which, in effect, do not include web toolbar buttons and advanced feedback features.
• When you have Google+ Injector installed, it will inject the the missing HTML, CSS, and JavaScript code -- the code which came from a spoofed user agent request.

Pros:

• Retains Opera user agent so that Google can count Opera's browser stats.

Cons:

• May not be future proof. If Google changes its code, then the code may need to be updated.