Technical SEO tools worth keeping around

Technical SEO is mostly about removing obstacles: crawlers should be able to reach the right URL, receive the right response, understand the page, and avoid duplicate or contradictory signals.

No single tool checks all of that. These are the small tools I would keep nearby, grouped by the problem they help investigate.

Status codes and redirects

• httpstatus.io checks status codes, response headers, and complete redirect chains for a list of URLs.
• Redirect Path shows 301, 302, 404, and 500 responses as you browse. It also catches client-side redirects and exposes headers, server details, and the IP address.

A redirect that works in the browser can still take three unnecessary hops. Seeing the whole chain is often the fastest way to spot that kind of problem.

International pages

• The hreflang testing tool checks annotations in HTML, HTTP headers, or an XML sitemap.
• The hreflang tags generator creates patterns for language and country variants using ISO language and country codes.

hreflang is easy to get almost right, which unfortunately still means wrong. Generate the tags if it saves time, then test the complete set of reciprocal links.

Structured data and markup

• Google’s Structured Data Markup Helper helps annotate page or email content so Google can understand the entities it contains.
• The Structured Data Testing Tool validates a pasted snippet or page.
• The W3C Markup Validation Service checks HTML and other web document formats for syntax errors.

Valid markup does not guarantee good structured data, and valid structured data does not guarantee a special search result. These tools tell you whether the implementation is understood, not whether Google owes it confetti.

Crawling and search data

• Screaming Frog SEO Spider crawls a site and collects URLs, titles, headings, canonicals, response codes, and other on-page details for an audit.
• Google Search Console reports how Google sees and finds the site, including search performance and indexing problems.
• Siteliner explores a site for issues such as duplicate content and broken links.
• Google’s Mobile-Friendly Test checks how easily a page can be used on a mobile device.

A crawler shows what should be happening across the site. Search Console shows what Google actually encountered. I would use both rather than treating either view as complete.

Performance

• WebPageTest runs a page in real browsers from different locations and connection speeds. Its waterfall, filmstrip, and advanced test options are particularly useful when a page feels slow but a single score does not explain why.
• PageSpeed Insights combines controlled lab measurements with field data when enough real-user data is available. Lab data helps debug; field data shows what visitors experienced.
• GTmetrix provides another performance report with loading details and optimisation suggestions.

Tool availability and URLs change, so check what is current before building a process around one of them. The durable part is the workflow: inspect the response, crawl the site, validate its signals, and look at both synthetic and real-user performance. A green score is pleasant. A site that can actually be crawled and used is better.