Run a 10-point SEO audit and HTML report via webhook and HTTP request

Description

Quick overview
This workflow exposes a GET webhook that accepts a website URL, fetches the page, runs a 10-point SEO checklist with a score out of 100, and returns a ready-to-share HTML audit report in the webhook response.

How it works
Receives a GET webhook request on the site-check endpoint with a url query parameter.
Validates and normalizes the input to allow only public domain URLs (no IPs, localhost, or internal TLDs).
Fetches the target page via an HTTP request using a custom User-Agent and an 8-second timeout.
Parses the returned HTML to evaluate 10 checks (reachability/response time, HTTPS, title length, meta description, viewport tag, single H1, image alt text coverage, Open Graph image, HTML lang attribute, and page size) and computes a score out of 100.
Builds a simple HTML report summarizing the score and pass/fail results for each check.
Responds to the webhook with the generated HTML report and a text/html content type.

Setup
Activate the workflow and copy the production webhook URL for the site-check endpoint.
Call the webhook with ?url=yourdomain.com (or ?url=https://yourdomain.com) and ensure the target site is publicly reachable from your n8n instance.
Optionally adjust the scoring thresholds, checks, timeout, and User-Agent in the workflow code and HTTP request configuration to match your audit criteria.

Requirements
An n8n instance (Cloud or self-hosted). No credentials or API keys are needed.

Customization
Change thresholds or add checks in the "Audit & build report" Code node, send the report by email with a Gmail node, or log every checked domain in Google Sheets to collect leads.

Additional info
Live example: https://worknull.app.n8n.cloud/webhook/site-check?url=n8n.io