How I Built an Autonomous Website Audit & Discovery Tool with FastAPI, React 19 & Google Gemini

PrajwalTheCoder — Tue, 20 Oct 2026 14:28:08 +0000

Cold outreach in 2026 is broken. Business owners get flooded every day with generic template spam like "Hey, I noticed your website could use an upgrade..."—with zero proof and zero personalization.

I spent the last month building an open-source alternative: Leddro 🚀

Instead of spamming businesses, Leddro discovers authentic local businesses, runs deep server-side diagnostics (DNS, TLS/SSL, TTFB speed, mobile responsiveness), and drafts fact-checked proposals that cite authentic audit findings.

🛠️ The Architecture & Command Center

1. Deterministic Local Discovery (OpenStreetMap)

Rather than scraping bloated or stale lead databases, Leddro queries public geographic registries (OpenStreetMap Overpass API) by commercial category and locality. It pinpoints real, verified businesses that either have zero web footprint or have broken websites.

2. Deep Diagnostic Probes

For businesses with a website, Leddro runs automated multi-vector checks:

DNS Records: Resolves A, AAAA, MX, and NS records to identify deliverability risks (missing SPF and DMARC policies).
TLS Handshake: Inspects certificate validity, cipher suites, and flags legacy protocols (TLS 1.0/1.1).
TTFB & HTTP Speed: Measures raw socket latency and Time-to-First-Byte down to milliseconds.
DOM & Mobile Check: Evaluates HTML viewport declarations and broken links.

3. Evidence-Grounded AI Proposals

Powered by Google Gemini 2.5 Flash (via free Google AI Studio keys), OpenAI, or local Ollama. The AI draft engine is strictly constrained to cite authentic finding IDs from the audit—eliminating hallucinated marketing claims.

4. Interactive Force-Directed Knowledge Graph

Built with D3.js force simulation, mapping real-time physical links between target businesses, DNS nameservers, AI engines, and Gmail dispatch gateways.

💻 Tech Stack

Backend: Python 3.12+, FastAPI, SQLAlchemy ORM, SQLite
Frontend: React 19, TypeScript, Vite, Tailwind CSS, D3.js
Integrations: OpenStreetMap Overpass, Google Gemini API, Gmail OAuth 2.0

🌟 Try It Out & Source Code

The entire project is 100% open source under the MIT License:

⭐ GitHub Repository: github.com/PrajwalTheCoder/Leddro
🌐 Interactive Demo Sandbox: prajwalthecoder.github.io/Leddro
📺 Full Video Walkthrough: Watch on YouTube

Would love to hear your feedback on the architecture, crawler safeguards, and scoring model in the comments!

DEV Community: PrajwalTheCoder