InjectGPT

🎥 Demo Video

▶️ Click the image to watch the demo

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InjectGPT is a Chrome extension that injects a custom system prompt, developer prompt, and model selection directly into ChatGPT requests.

Once configured, it always uses your chosen settings for every conversation.

For example, you can define a new system prompt and ChatGPT will permanently behave according to it.

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How It Works

The extension intercepts all /conversation requests at the network level, replacing the model, system prompt, and developer prompt with your current settings before they reach OpenAI’s servers.

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Features

• Model selection – switch between gpt-5-2, gpt-5-2-thinking, and other models
• Custom system prompt – define how the AI behaves
• Custom developer prompt – inject additional instructions after user messages
• Settings persistence – preferences are saved in localStorage

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Installation

1. Clone or download this repository
2. Open chrome://extensions
3. Enable Developer mode
4. Click Load unpacked
5. Select the extension folder

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Usage

1. Go to https://chatgpt.com
2. Press InjectGPT Settings
3. Change model and prompts
4. Start chatting

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Files

• manifest.json – extension configuration
• content.js – UI injection and settings management
• injector.js – network-level request interception
• styles.css – dark theme styling

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Note

⚠️ For educational purposes only.