Gmail Sender Icons is a Google Chrome extension that allows users to quickly identify the sender of email messages in Gmail without having to open the message. Developed by Greg Bradley, this free add-on falls under the category of Browsers and specifically the subcategory of Add-ons & Tools.

With Gmail Sender Icons, users can easily spot the official logo (favicon) of the sender's organization alongside the email message in their inbox. For example, if you receive an email from the extension will add a logo of the Google website next to the message, making it easier to identify the sender at a glance.

It's worth noting that all processing is done locally in your browser, ensuring that no Gmail data is ever shared or uploaded anywhere. The extension utilizes the Google S2 service for generating the website's favicon, while the Gmail messages are parsed with the Inbox SDK framework. Additionally, the add-on is open source, with the code available on Github for those interested in further exploration.