Before announcing a new website, check that its important pages load, links work, HTML is valid, and mobile performance is acceptable. After launch, keep monitoring availability and fix problems that affect real visitors.

These tools do different jobs. Five are mainly for quality assurance or monitoring. SoPilot is a directory-promotion assistant, not a technical site checker; its current offering includes paid plans. Treat directory submission as optional distribution, not a guaranteed SEO shortcut.

1. SiteOne Crawler: crawl pages and review site issues

SiteOne Crawler is an open-source crawler with desktop and command-line options. It can inspect a site for broken links and 404s, redirects, SEO and Open Graph metadata, headings, performance, accessibility, and security-related signals, then produce a report.

Use it after a redesign or before a launch: crawl the public site, review the pages with errors, fix high-impact issues, and crawl again. Check the crawl scope and request rate first, especially on production sites. Only scan websites you own or are authorized to test.

2. SoPilot: organize directory submissions selectively

SoPilot's directory submission assistant helps prepare and fill directory listing forms. Its site currently describes a freemium directory list and paid plans, so check current plan limits and terms before using it.

Do not submit blindly to hundreds of sites. Review each directory for a real audience, editorial standards, current activity, and a clear fit for your product. Prefer a small number of relevant listings that could bring customers. Google lists automated link creation and low-quality directory links among examples of link spam; see its link spam policy. A submission count or a promised backlink does not prove SEO value.

3. Unlighthouse: audit performance across many pages

Unlighthouse discovers pages and runs Lighthouse audits across a site, so you can compare performance and other Lighthouse signals in one report instead of checking only a single URL. The project is open source; its current documentation describes the CLI and the Node.js requirement.

Run a crawl on a representative set of pages, then prioritize repeat issues such as oversized images, render-blocking resources, or layout shifts. Lighthouse scores are diagnostic snapshots, not a guarantee of real-user speed or search rankings. Confirm important changes with field data when available.

4. lychee: find broken links before visitors do

lychee is an open-source link checker for Markdown, HTML, and other text formats. It can check local files or a live website, and the project provides a GitHub Action for repeatable checks in CI.

Run it on your content before publishing and periodically against the live site. External websites may rate-limit automated checks or temporarily fail, so review ambiguous results before removing a link. For a small site, even a scheduled link check can catch old redirects and dead references early.

5. Nu Html Checker: catch markup and document errors

Nu Html Checker checks HTML and can also check CSS and SVG. Use the online checker for a quick URL review, or run a local/service deployment for batch checks in a build workflow.

Fix meaningful errors such as malformed nesting, duplicate IDs, or invalid attributes. A clean checker report is useful, but it is not a certification that a site is accessible, secure, or search optimized. The checker itself describes its results as diagnostic and subject to change.

6. Gatus: monitor availability and alert on failures

Gatus is open-source monitoring software that you can self-host. It supports checks such as HTTP, DNS, TCP, and TLS, with configurable conditions and alert integrations. Its documentation covers endpoint checks and alerting.

Monitor the homepage and one critical action or API endpoint from a location that matters to your users. Set sensible intervals and thresholds, configure an alert destination, and test that the alert arrives. Monitoring tells you when a check fails; it does not diagnose every cause.

A simple pre-launch and maintenance routine

  1. Check discovery: confirm canonical URLs, robots.txt, sitemap, and important internal links.
  2. Crawl and validate: use SiteOne Crawler and lychee to find broken pages, redirects, and dead links; run Nu Html Checker on representative templates.
  3. Review page experience: use Unlighthouse to compare key pages, especially on mobile.
  4. Set up monitoring: use Gatus or another monitor to check availability and alert you when a critical endpoint fails.
  5. Promote with judgment: submit only to relevant directories and communities. Track referral visits and qualified inquiries rather than counting submissions or backlinks.
  6. Repeat after changes: rerun the checks after redesigns, deployments, major content edits, and infrastructure changes.

For crawlability and indexing basics, continue with the technical SEO checklist. For promotion and channel measurement, see growth and distribution.

Website launch is only the beginning. Check the site, fix issues that matter to people, watch availability, and promote where your intended audience actually looks.