Official Documentation

FastFiller Quickstart & Setup Guide

Everything you need to set up, customize, and master FastFiller in less than 2 minutes.

1 Installing FastFiller

Option A (Chrome Extension): Click Add to Chrome / Download Release and confirm installation. FastFiller will appear in your Chrome toolbar.

Option B (Developer / GitHub Release):

  1. Download the latest release ZIP from the FastFiller GitHub Releases.
  2. Unzip the archive to a permanent folder on your computer.
  3. Open Chrome and navigate to chrome://extensions.
  4. Enable Developer mode in the top right corner.
  5. Click Load unpacked and select the unzipped directory.

2 Connecting Free ChatGPT & DeepSeek Web Sessions

You do not need to pay for an API key. FastFiller can communicate directly with your logged-in AI web tabs:

ChatGPT Web Mode:

Simply have chatgpt.com open in any tab. FastFiller connects directly to your active browser login at zero cost.

DeepSeek Web Mode:

Keep chat.deepseek.com open. FastFiller connects directly to your logged-in DeepSeek web session for unlimited free form fills.

3 Configuring Custom API Keys (BYOK)

If you prefer sub-second dedicated API speeds, FastFiller supports direct BYOK keys and universal gateways:

  • Google Gemini (Gemini 3.5 Flash-Lite & 3.5 Flash): Ultra-fast free tier quota available at aistudio.google.com.
  • OpenCode Free (Space Bunny): 100% zero-auth free tier with no API key required.
  • Groq Free Dev Tier: Ultra-fast LPU inference (qwen3.8-27b, gpt-oss-120b).
  • OpenRouter: 19+ free models live, plus frontier commercial models.
  • DeepSeek API (Paid BYOK): DeepSeek V4 Flash (most popular) and V4 Pro.
  • OpenAI & Anthropic (Paid BYOK): Commercial paid endpoints (GPT-4o Mini, o3-mini, Claude 3.5/3.7 Sonnet).
  • Custom Gateway: Connect any provider or proxy (vLLM, LM Studio, Together, corporate proxies) with both free and paid endpoints supported.

Keys are stored strictly in your browser's chrome.storage.local and never transmitted to our servers.

4 100% Offline Local LLMs (Ollama)

For maximum corporate security and zero data exfiltration:

  1. Install Ollama from ollama.com.
  2. Start your preferred model: ollama run llama3
  3. In FastFiller Settings, set Provider to Ollama (Local) with endpoint http://127.0.0.1:11434.
  4. Zero network bytes leave your machine during form fills.