Riff is a Chrome extension that generates replies, direct messages, and original posts for social media platforms including X, LinkedIn, Facebook, and Instagram. It runs on Google's Gemini Nano AI model directly within the Chrome browser, processing data locally on the user's computer. This local operation eliminates the need for external servers, API keys, or a subscription fee. The extension is designed to assist with drafting content, but it does not post or send messages automatically; the user retains full control over publishing. The extension resides in Chrome's side panel, accessible from the toolbar or with the Alt+Shift+R shortcut. To generate a reply, the user selects a post and provides a general point or rough notes. Riff reads the context of the post or conversation and drafts a response. Users can adjust the output by setting parameters for tone, including how smart, salesy, or adventurous the draft should be. Revisions can be requested using plain text commands such as "shorter" or "end with a question," or by selecting rework chips like Punchier, Bolder, or More Human. Additional features include generating multiple opening line options through a "Pick a hook" function and the ability to leave the input empty in a DM to have the tool answer based solely on the received message. For creating original posts, the user inputs rough notes into the side panel, and Riff generates a draft that can be refined through iterative commands before being inserted into the post box. The tool is compatible with Chrome on Windows, Mac, Linux, and Chromebook Plus. It is presented as a drafting assistant for social media communications, emphasizing local processing and user oversight of all published content.