There is no definitive answer to what is the biggest feature of a browser, as different browsers may have different strengths and weaknesses. Some common features that users may look for in a browser are:

Speed: how fast a browser can load web pages and run web applications.

Compatibility: how well a browser can support various web standards and technologies.

Security: how well a browser can protect users from malicious websites, trackers, and hackers.

Privacy: how well a browser can respect users’ personal data and preferences.

Customization: how much a browser can be modified with extensions, themes, and settings.

What feature is most important to you?