SEO Audit Tools: Screaming Frog, Sitebulb, Ahrefs, Semrush and Free Options
“Which SEO tool should I buy?” is one of the questions I hear most. The answer is almost always the same: first decide what job you need done. A site crawler and a platform with a backlink database do not answer the same question.
This article compares the most common audit tools alongside the free Google tools, framed as “which one for which situation”. I do not list prices; plans change often, so check each tool's official site. There is no sponsorship here.
Short answer: Every audit starts with the free Google Search Console and PageSpeed Insights. To crawl a site like Googlebot, you pick a crawler such as Screaming Frog or Sitebulb; for scheduled cloud audits with backlink and competitor data, a platform such as Ahrefs or Semrush. The right tool depends on site size and the job at hand.
Before choosing a tool: which audit job?
An SEO audit works with four kinds of data. Each tool is strong in one or several of them.
The technical SEO guide explains the overall scope of an audit and the order to work in. A tool is only the execution side of that scope.
Free SEO audit tools
You can run a very good initial audit without a budget. These are the tools I open first on every project:
- Google Search Console: Indexing, performance, sitemaps and URL Inspection. The only source that shows how Google sees your site. I explain the reports in the Google Search Console guide.
- PageSpeed Insights: Shows real-user data (Chrome UX Report) where available alongside a Lighthouse lab test.
- Lighthouse: Built into Chrome DevTools; runs performance, accessibility and basic SEO checks.
- Rich Results Test: Shows whether Google can read your structured data and which rich results it is eligible for.
- Ahrefs Webmaster Tools: According to Ahrefs' official site, it offers a free site audit and backlink view for websites you verify.
- Screaming Frog free version: According to its official site, it crawls up to 500 URLs; enough for small sites.
I cover the Core Web Vitals thresholds (LCP ≤ 2.5 s, INP ≤ 200 ms, CLS ≤ 0.1) and measurement differences in the Core Web Vitals article.
Desktop crawlers: Screaming Frog and Sitebulb
Screaming Frog SEO Spider is a crawler you install on your computer. Fast access to raw data, custom extraction, filtering and flexible exports make it one of the most widely used tools among technical SEOs. The free version is capped at 500 URLs; a licence is needed for larger crawls and advanced features.
Sitebulb is also a crawler but takes a different approach. According to its official site it comes as desktop (Windows and Mac) and cloud products; it presents findings as prioritised, explained “hints” and produces visualisations such as crawl maps plus customisable PDF reports. Those explanations save time when you need to brief a client or developer.
Cloud platforms: Ahrefs and Semrush
Ahrefs and Semrush are cloud platforms that bundle site audits with backlink, keyword and competitor data. They crawl on their own servers, so your computer need not stay on, and you can schedule recurring audits.
According to Ahrefs' official page, Site Audit checks for more than 170 technical and on-page issues. According to Semrush's knowledge base, Site Audit runs more than 140 checks and, as of October 2026, includes a separate category for visibility in AI search. Crawl capacity depends on the plan for both; Semrush's free account is limited to 100 pages a month.
Their real difference is not the audit but the external data. If you also need backlink analysis and competitor comparison, one subscription can cover both auditing and research.
Which SEO tool for which job?
| Need | Suitable tool | Why |
|---|---|---|
| Google's indexing decisions | Search Console | The only source with data straight from Google |
| Deep technical crawl, custom extraction | Screaming Frog | Flexible raw data access and exports |
| Prioritised findings and reports | Sitebulb | Explained hints, visualisations, PDF reports |
| Audit + backlink + competitor data | Ahrefs or Semrush | External data and scheduled audits in one place |
| Page speed and Core Web Vitals | PageSpeed Insights, Lighthouse | Field and lab data |
| Structured data validation | Rich Results Test | Whether Google reads the markup |
For a small corporate site, Search Console, PageSpeed Insights and the free Screaming Frog are often enough. For an e-commerce site with thousands of products, a licensed crawler plus a cloud platform works better. For special checks like hreflang, see the audit steps in hreflang and international SEO.
How to prioritise tool findings
Health scores and warning counts can mislead: thousands of “missing meta description” warnings matter less than one wrong noindex. Rank findings by business impact.
- Start with Search ConsoleFind important pages that are not indexed and traffic losses.
- Crawl the siteExtract status code, redirect, canonical and internal link issues.
- MatchCompare crawl findings with pages that drive traffic and conversions.
- PrioritiseBuild a to-do list ranked by impact and effort.
- Measure againRecrawl after fixes and monitor in Search Console.
To present findings clearly to management, use the framework in the SEO reporting guide. The schema generator among the site's free SEO tools helps close structured data gaps found in an audit.
When do you need an expert rather than a tool?
Tools list problems; they do not decide which ones actually hurt your traffic, which are deliberate choices or in what order to fix them. In a sudden traffic drop, a site migration or large catalogue issues, interpretation is worth more than the tool.
To interpret your tool outputs together or commission a full technical audit, see SEO consulting or book an intro call.
Frequently Asked Questions
Is one SEO tool enough?
For small sites, Search Console plus a crawler is often enough. No third-party tool replaces Search Console, because only it shows Google's indexing decisions. Paid tools make sense once you need scale and external data.
Does a tool's health score reflect Google rankings?
No. A health score is a summary calculated by the tool's own rules, not a Google ranking signal. Rather than silencing trivial warnings to raise the score, focus on issues that affect pages bringing traffic.
Are Ahrefs and Semrush traffic estimates reliable?
These numbers are estimates based on their own datasets and are useful for competitor comparison. For your own site's real click data, rely on Search Console, and on GA4 for user behaviour.
How often should I run an SEO audit?
A full audit once or twice a year is a reasonable rhythm for most sites. Weekly or monthly automated cloud crawls catch new broken links and redirect errors early. Always run an extra audit after a migration or a major release.
Will a crawler slow down my site?
High-speed crawling can strain small servers. Crawlers let you limit concurrent requests and speed; crawling a live site outside peak hours is a good habit.
Do these tools measure visibility in AI search?
Some platforms have added modules that track AI bot access and visibility in AI answers, but methods vary by tool. I explain how I approach this in brand visibility in ChatGPT.
8+ years of hands-on SEO and GEO experience across 150+ projects in e-commerce, SaaS, healthcare and local business sectors. Writes based on real client data, not theory.