Custom Button is a Chrome add-on developed by Rubén Martínez that allows users to create and customize buttons for easy access to their favorite websites. With this add-on, users can set a custom URL to open on click, choose whether the website should open in the current tab, new tab, new window, new popup window, or even as a popup on the button itself.

One of the key features of Custom Button is the ability to change the icon of the button, giving users the freedom to personalize their browsing experience. Additionally, users can set specific domains where the button should work using regular expressions. This ensures that the button only appears on the websites that users want it to.

Furthermore, Custom Button provides a convenient notification feature that alerts users when the current domain doesn't match the specified domains. This helps users stay aware of their browsing context and prevents accidental clicks on the button.

Overall, Custom Button is a useful add-on for Chrome users who want to have quick and easy access to their favorite websites. With its customizable options and intuitive interface, it provides a seamless browsing experience.