There is no shortage of website audit tools. But most comparisons are either written by a vendor selling one of them, or list features without saying what each tool is actually good for. This is a neutral breakdown of the six most commonly used tools in 2026, including what each one measures, who it is designed for, and where it has 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. 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 around $117 per month billed annually, or about $140 month-to-month. 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 a free option for site owners who want basic audit access without a subscription. Paid plans are available at several tiers; the platform is priced for teams that need ongoing SEO and competitive data, not one-time assessments.

Woorank

Woorank is designed for non-technical users. Enter a URL and get a structured report covering SEO basics, mobile usability, security, and social signals. The interface is cleaner and simpler than Semrush or Ahrefs, which makes it a reasonable starting point for business owners who need a quick read without navigating a complex platform. It does not go as deep as dedicated SEO tools on technical crawl analysis or backlink data. Plans start around $80 per month.

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 add more test locations and scheduled monitoring.

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. Stackra is free. It is aimed at small business owners and marketing teams rather than agencies managing large volumes of sites.

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 Woorank when you want a simpler interface 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.