This guide compares six website audit tools for small business owners. It is written for readers weighing a free Semrush alternative, an Ahrefs alternative, or pricing before committing to a paid platform. A website audit tool is software that scans a website and reports on issues affecting search rankings, performance, accessibility, and user trust. This guide covers six of them: Google Lighthouse, Semrush, Ahrefs, Ubersuggest, GTmetrix, and Stackra. A few, like Semrush and Ahrefs, are industry standards used by millions. Stackra is a newer, much smaller entrant, and it is mine. Full disclosure: this comparison is written by the founder of Stackra, one of the six tools covered here. That means you should weigh the Stackra section with that in mind. What it also means is that I have spent considerable time studying what each of these tools actually does well and where they fall short. The goal is to give you an honest, structured breakdown of each tool: what it measures, who it is designed for, and where it has limits, so you can pick the one that fits your situation.
Six tools at a glance
The summary table below shows what each tool covers, who it is built for, and where it falls on the price scale. Detailed write-ups for each tool follow.
| Tool | Price | Best for | Scope | Output format |
|---|---|---|---|---|
| Google Lighthouse | Free | Single-page technical baseline | One URL at a time, including AI-agent checks | Issue list with category scores |
| Semrush | Free plan; from $139/mo | Agencies managing multiple sites | Full-site crawl + keywords + backlinks + AI answer tracking | Severity-grouped issues |
| Ahrefs | Free (Ahrefs Free, formerly Webmaster Tools); from $29/mo, Site Audit from $129/mo | Backlink and competitor research | Full-site crawl + link index + AI tracking add-on | Errors, warnings, notices |
| Ubersuggest | From $29/mo; lifetime option | Beginners wanting keywords plus a simple audit | Domain overview + keyword data + site audit + AI answer tracking | Plain-language report + keyword ideas |
| GTmetrix | Free; from $4.99/mo | Diagnosing slow load times | Single-page speed + monitoring | Waterfall chart + tips |
| Stackra | Free plan; from $19/mo | Small business owners wanting business-focused recs | Up to 20 pages, three pillars + linked domains, traffic, keywords | Scored report + prioritized action plan |
Prices as listed on each vendor's pricing page, checked September 2026, month to month unless noted. Annual billing is cheaper, and free tiers have tighter limits.
Google Lighthouse
Lighthouse is a free, open-source tool built into Chrome DevTools and available as a command-line tool or via Google PageSpeed Insights. It measures performance, accessibility, SEO, and best practices for a single page. It is widely used because it is free, fast, built into Chrome, and closely aligned with how Google evaluates pages in its own tools. Version 13, released in 2026, added an agentic browsing category that checks how well a page works for AI agents. The main limitation is scope: it tests one URL at a time, does not track changes over time, and gives you a list of issues without telling you what to fix first.
Semrush
Semrush is an enterprise SEO platform with a site audit module. It crawls your entire site and flags technical issues: broken links, duplicate content, missing tags, redirect chains. It also covers keyword research, backlink analysis, and competitor tracking in the same subscription. It is the most popular choice among agencies managing multiple client sites. Paid plans start at $139 per month, or $117.33 per month billed annually, and a free plan allows 10 reports a day on one project. Plans from $199 per month also track how your brand appears in AI answers from ChatGPT, Perplexity, and Gemini. Issues are grouped by severity, but the total volume can be large and the interface takes time to learn for smaller teams.
Ahrefs
Ahrefs is best known for its backlink index, one of the largest in the industry. Its Site Audit tool crawls your pages and segments findings into errors, warnings, and notices. Where Ahrefs stands out is in competitive research: you can see exactly what keywords competitors rank for and which pages earn the most backlinks. Ahrefs Webmaster Tools is free for verified site owners and includes Site Audit. Paid plans start at $29 per month for Starter, which covers research rather than audits; Site Audit comes with Lite at $129 per month and up. Tracking your brand in AI answers (Brand Radar) is a paid add-on from $199 per month. The platform is priced for teams that need ongoing SEO and competitive data, not one-time assessments.
Ubersuggest
Ubersuggest is Neil Patel's SEO tool, built to be cheap and approachable for beginners. Enter a domain and you get keyword ideas, traffic estimates, a backlink overview, and a site audit that flags common on-page and technical issues in plain language. It is the most beginner-friendly of the paid tools here: plans start at $29 per month, with a one-time lifetime option, and it now tracks where your brand appears in AI answers from ChatGPT, Gemini, Perplexity, and Google AI Overviews. It does not match Ahrefs or Semrush on backlink depth or large-site crawls, and its data is less comprehensive, but for a solo owner or small team that wants keyword ideas plus a basic audit without a steep price or learning curve, it is a sensible starting point.
GTmetrix
GTmetrix is a pure performance tool. It measures how fast your page loads, shows a waterfall chart of every resource request, and breaks down the largest contributors to slow load time. It is not a full-site SEO audit tool. Use GTmetrix when you already know your site is slow and need to diagnose exactly which files, scripts, or third-party requests are causing the problem. A free plan is available with limited test frequency. Paid plans start at $4.99 per month billed yearly ($5.99 month to month) and add more tests, test locations, scheduled monitoring, and an MCP server for running tests from AI assistants.
Stackra
Stackra crawls up to 20 pages and produces a scored report across three pillars: Conversion & Trust (marketing and trust), Search Visibility (SEO), and Technical Confidence (performance and security). Each pillar is reviewed by an AI persona for that specialty: a CMO, an SEO expert, and a CTO. The report includes a scored summary and a prioritized action plan. Every scan, Free included, also shows how many keywords you rank for, your estimated search traffic, how many sites link to you, your top 3 keywords, and AI search visibility signals. Paid plans add your full keyword list (up to 50, with position, monthly searches, and the page that ranks), a keyword plan grouped by theme, who links to you with each site's link authority, and a side-by-side competitor comparison. Every plan can connect Google Search Console, Analytics, and Bing. Stackra has a free plan (5 scans a month) plus paid Starter ($19/mo) and Pro ($49/mo) tiers. It is aimed at small business owners and marketing teams rather than agencies managing large volumes of sites.
How established is each tool, by the numbers
Here is a data point no other comparison will hand you. One honest way to gauge how established a tool actually is: count how many other websites link to it. We measured that for the tools here using the Common Crawl web graph, an independent open crawl of the web. It is a rough proxy for brand footprint, not a measure of audit quality, but it cleanly separates the industry standards from the newcomers, us included. Google Lighthouse sits off this scale entirely because it lives on Google's own domain.
We put Stackra at the bottom of this table on purpose. A tool comparison that quietly inflates its own author is exactly what this guide is meant to help you see through.
| Tool | Referring domains | What it says |
|---|---|---|
| Ahrefs | 122,000 | The most-linked, and growing fastest |
| Semrush | 66,000 | The established leader |
| Ubersuggest (neilpatel.com) | 36,000 | Wide reach, heavily marketed |
| GTmetrix | 18,000 | A well-known performance tool |
| Stackra | under 10 | New. We are not going to pretend otherwise. |
Referring domains counted from the Common Crawl web graph, July to September 2026. This measures how established a brand is across the open web, not how good its audit is. Source: Stackra analysis of the Common Crawl web graph.
How to choose
Use Lighthouse when you want a free, fast technical baseline for a single page. Use GTmetrix when you need to diagnose slow load times specifically. Use Semrush or Ahrefs when you are managing SEO at scale across multiple sites or clients and need keyword and backlink data alongside technical audits. Use Ubersuggest when you want keyword ideas and a basic audit at a low price without a steep learning curve. Use Stackra when you want a full-site assessment with business-focused recommendations and a clear starting point for improvement.
The best tool is the one whose output you will actually act on.
Frequently asked questions
Common questions about choosing and using website audit tools, with answers that apply across the six tools above.
What is a website audit tool?
A website audit tool is software that scans a website and reports on issues affecting search rankings, performance, accessibility, and user trust. Most tools fall into one of three groups: pure performance testers (Lighthouse, GTmetrix), enterprise SEO platforms (Semrush, Ahrefs), and affordable SMB tools (Ubersuggest, Stackra). Choose the category first based on what you need to learn, then pick the specific tool based on price and team size.
What is the best free website audit tool?
For a single-page technical baseline, Google Lighthouse and PageSpeed Insights are the most widely used free tools and are the closest to how Google itself evaluates pages. For a full-site audit with prioritized recommendations, Stackra has a free plan that covers up to 20 pages. Ahrefs Free (formerly Ahrefs Webmaster Tools) is also free for verified site owners and is best when you specifically want backlink data. The best free tool depends on whether you need depth on one page (Lighthouse), full-site coverage (Stackra), or backlink visibility (Ahrefs Free).
Is Lighthouse a website audit tool?
Yes. Lighthouse is Google's open-source auditing tool, available in Chrome DevTools, as a command-line tool, and through Google PageSpeed Insights. It tests a single URL across performance, accessibility, SEO, and best practices, and gives each category a score out of 100. Lighthouse is the technical baseline that most other audit tools either embed, reference, or compete with. It is free to use with no account required.
How is Stackra different from Semrush?
Semrush is an enterprise SEO platform built for agencies and in-house teams managing multiple client sites at scale. It bundles keyword research, backlink analysis, competitor tracking, and a full-site technical audit module into one subscription, with paid plans from $139 a month and a free plan capped at 10 reports a day. Stackra is a single-site audit with a free plan, aimed at small business owners and marketing teams who want a scored Growth Readiness report with a prioritized action plan, not a multi-tool platform. Every Stackra scan still shows how many keywords you rank for and your estimated search traffic, and every plan can connect Google Search Console; what it does not offer is a keyword database you can point at any term or domain. Semrush is broader and deeper for ongoing SEO work; Stackra is faster and more focused for one-time and quarterly assessments.
What is the best free Semrush alternative?
Honestly, no free tool replaces Semrush end to end. Semrush bundles a paid keyword database, a backlink index, rank tracking, and a full-site crawler in one platform. Free options cover individual slices, not the platform itself. By slice:
- •Keyword volume: Google Keyword Planner (free with a Google Ads account, returns ranges not exact figures)
- •Backlinks on your own site: Ahrefs Free, formerly Ahrefs Webmaster Tools (free for verified site owners)
- •Search position for your own pages: Google Search Console (free, shows queries you already rank for)
- •Technical audit: Google Lighthouse for a single page, or Stackra for a full site up to 20 pages (with your top keywords and linked domains on every scan, not a keyword database)
What is the best free Ahrefs alternative?
Same honest answer: no free tool replaces Ahrefs end to end. Ahrefs is paid because it runs one of the largest backlink indexes in the industry, and that data has no free equivalent. Free options cover specific tasks:
- •Backlinks on your own site: Ahrefs Free, formerly Ahrefs Webmaster Tools (free for verified site owners only)
- •Search position for your own pages: Google Search Console (free)
- •Keyword volume estimates: Google Keyword Planner (free with a Google Ads account)
- •Technical audit: Google Lighthouse for a single page, or Stackra for a full site up to 20 pages (every scan counts the sites linking to you and paid plans list them, a much smaller backlink view than Ahrefs)
How does Ahrefs pricing compare to free alternatives?
Ahrefs paid plans are tiered by user seats and project limits, built for teams running ongoing SEO and competitive research. Free options exist for slices, not the platform. Pricing in context:
- •Semrush: from $139 per month, or $117.33 billed annually, plus a limited free plan
- •Ubersuggest: from $29 per month, with a lifetime-license option
- •Ahrefs: Ahrefs Free (formerly Webmaster Tools) for verified site owners, then from $29 per month for research and $129 per month for Site Audit
- •Free combination: Google Search Console plus Lighthouse plus a free audit tool, scoped to your own site
How often should I run a website audit?
A full audit every quarter is a good baseline for most small business websites. Run an additional audit before and after any major change: a redesign, a platform migration, a new product or service launch, or a significant content update. If you are running active marketing campaigns, monthly checks on speed, broken links, and form functionality help catch problems before they cost you leads. Most tools listed above can be re-run on demand.
Do website audit tools fix issues automatically?
No. Every tool listed above only finds and reports issues. The fixes are still up to you, your developer, or your platform settings. The exceptions are issue-specific managed services (image-compression apps on Shopify, caching plugins on WordPress) that automate one narrow area, not the audit itself. When choosing a tool, weight the report quality and the prioritization of recommendations more heavily than the raw issue count, because the work to fix issues is what actually moves the score.
Compare Stackra directly against these
If you are weighing a specific product rather than the category, these pages go side by side on price, output and who each one is actually built for. Each one leads with where the other option is genuinely better.