Free Technical SEO Tools for Bloggers: Open Source and Screaming Frog Alternatives

You can cover almost every technical SEO check a blog needs without paying for a tool. Google Search Console tells you what Google actually indexed, a desktop crawler shows you what a search engine finds when it walks your links, and a handful of free testers handle speed, structured data, and robots.txt. The paid suites mostly add scale, scheduling, and convenience on top of the same checks.

The catch is that no single free tool does everything, and most "free SEO tool" lists don't tell you which one to open for which problem. This guide is organized by job instead of by brand, so you can build a small stack that fits a blog with dozens or a few hundred posts.

Start With the Free Tools Google and Bing Already Give You

Before installing anything, use the two tools that see your site from the search engine's side. A crawler can only guess what Google will do. These report what it did.

Google Search Console is the one tool every blog should have. The Page indexing report lists which URLs are indexed and why the rest aren't, the URL Inspection tool shows how Google sees a single page, the Sitemaps report tells you whether your sitemap could be fetched, and the robots.txt report shows the robots.txt files Google found for your site. The Performance report adds clicks, impressions, and positions, though it has its own counting rules worth learning before you trust a trend.

Bing Webmaster Tools is worth adding even if Bing sends you little traffic, because of one feature: Site Scan. It crawls your site on demand and groups what it finds into errors, warnings, and notices. You set a limit on how many pages each scan covers. For a blog with no budget, it's the closest thing to a hosted site audit with no paid tier attached.

Ahrefs Webmaster Tools (now branded Ahrefs Free) is the third free account worth creating. Once you verify your site, it gives you 5,000 Site Audit crawl credits per verified project per month, and only HTML pages that return a 200 status use credits. It also shows up to 1,000 of your backlinks at once, which overlaps with the free ways to check backlinks we've covered before.

The one limit shared by all three: they only work on sites you can verify. That's fine for auditing your own blog, but you can't point them at a competitor.

Which Free Tool Handles Which Technical SEO Job?

Here's the stack mapped to the checks a blogger actually runs. Every tool in the table has a free option that covers a typical blog.

| Job | Free tool | What it tells you | | --- | --- | --- | | Is the page indexed, and if not, why? | Search Console (Page indexing, URL Inspection) | Google's own verdict, per URL | | Broken links, redirects, duplicate titles | Screaming Frog (free, 500 URLs) or SEOnaut | What a crawler finds following your links | | Site-wide issue scan, hosted | Bing Site Scan, Ahrefs Site Audit | Errors and warnings without installing anything | | Page speed and Core Web Vitals | PageSpeed Insights, Lighthouse, Unlighthouse | Lab scores, plus field data when Google has it | | Structured data | Rich Results Test, Schema Markup Validator | Whether markup parses, and whether it qualifies for a rich result | | robots.txt and sitemaps | Search Console robots.txt and Sitemaps reports | Whether Google could fetch and read them |

Two notes on the table. First, the crawler row is where most people reach for a paid tool, and it's the row where free options are most capable. Second, the structured data row has two tools on purpose. The Rich Results Test checks Google's eligibility rules, while the Schema Markup Validator checks schema.org syntax. They answer different questions, and the difference matters more now that Google has cut back rich results.

When Is Screaming Frog's Free Version Enough?

Screaming Frog's SEO Spider is the desktop crawler most technical SEO guides assume you have. Its pricing page lists one restriction for the free version: a crawl limit of 500 URLs. The paid licence, listed at $279 per year for one user, removes that cap. The rest of the feature list is shown as the same for both.

For a lot of blogs, 500 URLs is plenty. Our own sitemap at trafficmonitor.app lists 67 URLs today, so a full crawl of the site fits comfortably inside the free tier. The question to ask is how many URLs a crawl discovers, not how many posts you've written. Tag pages, category archives, author pages, paginated lists, and parameter URLs all count. A WordPress blog with 150 posts can easily expose several hundred crawlable URLs once archives are included.

If you're near the cap, Screaming Frog's own crawling guide suggests unticking images, CSS, JavaScript, and external links so the crawl focuses on internal HTML pages. You can also crawl one section at a time.

What the free crawl is good at:

• Finding internal links that point at 404s or at URLs that redirect, which feeds straight into a redirect chain cleanup
• Listing duplicate title tags and meta descriptions across the whole site in one export
• Spotting pages that are hard to reach by clicking, the first step of an internal linking audit

What it can't tell you is whether Google cares. A crawler reports that a page is reachable. Only Search Console reports that Google indexed it.

Open Source Screaming Frog Alternatives

If you'd rather not install closed-source software, or you've outgrown 500 URLs and don't want a yearly licence, two open source projects are worth knowing. Both are MIT-licensed.

SEOnaut is a self-hosted site auditor written in Go with a MySQL database. The project recommends running it with Docker, which starts a local web app (on port 9000 by default) where you add a site and run a crawl. It reports broken links, temporary and permanent redirects, redirect loops, missing or duplicate meta tags, and headings in the wrong order, and sorts issues into critical, high, and low severity. There's also a hosted version at seonaut.org if you don't want to run Docker. It's the closest open source match to a desktop crawler's core audit.

Unlighthouse solves a different problem. Google's Lighthouse, which is itself open source, audits one page at a time. Unlighthouse finds the pages on your site from your sitemap and internal links, runs Lighthouse on each, and shows the results in a local dashboard as they come in. One command starts it:

npx unlighthouse --site yourblog.com

It needs Node.js 22.18 or later and Chrome (it downloads Chromium if Chrome is missing). It also samples similar pages, such as blog posts that share a template, so a large blog doesn't take forever. For a blogger, this is the fastest way to find the one template or plugin that's slowing every post down.

The trade-off with both is setup time. Neither is as polished as a commercial crawler, and you're responsible for keeping them updated. In exchange, there's no URL cap beyond what your machine can handle.

A Free Technical SEO Routine for a Blog

Tools only help if you open them on a schedule. Here's a routine that uses the free stack and takes about an hour a month for a blog with a few dozen to a few hundred posts.

1. Monthly, in Search Console: open the Page indexing report and check whether the count of indexed pages moved. If a group of posts dropped out, inspect two or three of them before changing anything. A sitemap that could not be read shows up in the Sitemaps report first.
2. Monthly, with a crawler: run Screaming Frog's free crawl, SEOnaut, or Bing Site Scan. Fix broken internal links and links to redirecting URLs first, since those are entirely in your control.
3. After any theme or plugin change: run Unlighthouse or PageSpeed Insights on a few post templates. Speed regressions usually arrive with a change you made, not on their own.
4. After adding or editing schema: test one URL in the Rich Results Test, then check a second post using the same template. Markup that's broken on one post is usually broken on all of them.
5. Quarterly: run a content audit using the crawl export and Search Console data together. The crawl tells you what exists; Search Console tells you what earns impressions.

If your robots.txt or sitemap ever changes, check the robots.txt report and test the file before Google trips on it.

Where Free Tools Stop Being Enough

The free stack covers the checks. What it doesn't do is watch your site between checks. Every tool above answers "what's true right now," and every one of them waits for you to remember to look.

That gap matters most for traffic. A technical problem rarely announces itself in a crawl report first. It usually shows up as a post quietly losing clicks a week or two after a change. Search Console has that data, but you only notice it if you compare date ranges by hand, and the Search Console API can automate the pull if you're comfortable with code.

If you'd rather be told, Traffic Monitor connects to Search Console with read-only access, pulls clicks, impressions, and CTR for each post every day, and keeps that history so a drop shows up as a change instead of something you discover a month later. It doesn't replace the crawler or the testers above. It covers the part they don't: noticing that something moved.

The Short Version

You don't need a paid suite to do technical SEO on a blog. Start with Search Console, add Bing Webmaster Tools for Site Scan and Ahrefs Webmaster Tools for a second audit and a backlink view. Use Screaming Frog's free version while your crawl stays under 500 URLs, and switch to SEOnaut if you outgrow it or want something open source. Use Unlighthouse to run Lighthouse across every page, and the Rich Results Test plus the Schema Markup Validator for structured data.

Then put the checks on a calendar. The tools are free. The habit of opening them is the part most blogs skip.