Tweak

Tweak any webpage with a prompt.

For example:

• Hide all headlines about the NBA
• Convert this page to dark mode
• Change the font style to inter

Getting started

1. Clone the repo

git clone https://github.com/willhennessy/tweak.git
cd tweak

No build step required. This is a plain HTML/CSS/JS extension.

2. Load the extension in Chrome

1. Open chrome://extensions
2. Enable Developer mode (toggle in the top right)
3. Click Load unpacked
4. Select the tweak folder

3. Add your API key

1. Click the Tweak icon in your toolbar
2. Paste your Anthropic API key and save
3. Pin the Tweak icon in your toolbar

4. Use it

1. Navigate to any webpage
2. Click the Tweak icon
3. Type a visual change (e.g. "make the follow button green")
4. Press Apply or Cmd+Enter

Applied tweaks are saved per domain and re-injected automatically on future page loads. You can toggle or delete them from the Active tab in the popup.

Requirements

• Chrome 116+
• Anthropic API key (Claude)
• coming soon: Codex API key
• coming soon: freemium model, no API key required

How it works

Tweak sends the page's HTML and your prompt to Claude, which returns a CSS ruleset. The extension injects that CSS directly into the page using Chrome's scripting.insertCSS API — no eval, no JavaScript execution, no CSP issues.

Tweaks are stored in chrome.storage.local keyed by domain and re-applied via a tabs.onUpdated listener on each page load.

Project structure

manifest.json   Chrome extension manifest (MV3)
background.js   Service worker — handles Claude API calls and CSS injection
content.js      Content script — manages tweak storage per domain
popup.html/js   Extension popup UI
options.html/js API key settings page