How to Run a Website Performance Audit (2026 Checklist)

A website performance audit is a structured check of how fast, stable, accessible, findable and persuasive your site is for real visitors and for the search and AI systems that send them. Run through the checklist below in order, record a pass or fail against each item, then fix the failures that cost you the most traffic and revenue. Most teams can complete a first pass in a day using free tooling.

Performance is no longer a single number. A useful 2026 audit covers six layers: Core Web Vitals, site speed, technical SEO, accessibility, answer engine optimisation and conversion. Here is what to check in each.

1. Core Web Vitals

Core Web Vitals are Google's three real-user metrics for loading, responsiveness and visual stability. Google measures them at the 75th percentile of page views, so a metric only passes when at least 75% of visits hit the good threshold. The current official thresholds, unchanged into 2026, are:

• Largest Contentful Paint (LCP): good is 2.5 seconds or less. This measures how quickly the main content loads.
• Interaction to Next Paint (INP): good is 200 milliseconds or less. This measures responsiveness across every interaction in a visit. INP replaced First Input Delay in March 2024 and is the most commonly failed of the three. Industry estimates suggest roughly 43% of sites fail the threshold.
• Cumulative Layout Shift (CLS): good is 0.1 or less. This measures how much the page jumps around as it loads.

Pull your field data from the Chrome User Experience Report and the Core Web Vitals report in Search Console for site-wide trends, then use PageSpeed Insights and Lighthouse to diagnose individual pages. Field data tells you whether you have a problem. Lab data helps you find the cause.

2. Site speed and front-end weight

Core Web Vitals are symptoms. Site speed work is where you fix them. Check for oversized images served without modern formats or correct dimensions, render-blocking scripts and stylesheets, fonts that delay text rendering, and third-party tags that pile on after load. Confirm your server response is quick, your assets are served from a CDN and your largest images are compressed and lazy-loaded below the fold. Mobile speed deserves its own pass, since it gates a large share of B2B traffic.

3. Technical SEO

If search engines cannot crawl, index and trust your pages, none of the speed work matters. Work through:

• Crawlability and indexing: a valid robots.txt, a clean XML sitemap, correct canonical tags and no pages accidentally set to noindex.
• Redirects and links: every redirect resolves in a single 301 hop with no chains, and there are no broken internal links.
• Security and structure: HTTPS enforced site-wide, a logical URL structure, sensible internal linking and no duplicate titles or content.
• Structured data: valid schema markup with no errors flagged in testing tools.

4. Accessibility (WCAG 2.2 AA)

WCAG 2.2 is the current W3C recommendation, with 86 success criteria, and AA is the tier most regulations point to. Treat AA as best practice and future-proofing rather than a settled legal requirement everywhere, since the EU's harmonised standard and the US DOJ Title II rule still reference WCAG 2.1 AA with compliance dates running into 2027 and 2028. The newer 2.2 criteria worth checking include:

• Keyboard focus is always visible and never hidden behind sticky headers or footers.
• Interactive targets are at least 24 by 24 CSS pixels.
• Any drag action has a simple tap or click alternative.
• Login does not force a memory test, for example by offering an emailed magic link.

Run an automated scan first, but do not stop there. Tools such as axe-core catch only around 57% of issues by volume, so the rest needs manual keyboard and screen-reader testing. For context on how common failures are, the WebAIM Million 2026 analysis reportedly found detectable WCAG failures on about 95.9% of top home pages, with low-contrast text alone affecting roughly 83.9%. A scan tells you where to start, not whether you are done. Our website audit pairs automated scanning with manual testing for exactly this reason.

5. Answer Engine Optimisation (AEO)

AEO is the work of making your content easy for AI answer systems such as Google AI Overviews, ChatGPT, Perplexity and Claude to interpret, trust and cite. It matters more each quarter: industry estimates suggest AI Overviews now appear in around 55% of searches, and Gartner has predicted traditional search volume could fall by roughly 25% by 2026 as people lean on AI assistants. Where SEO works at page level, AEO works at fact level. Check that you:

• Lead each section with a direct answer of around 40 to 60 words, since AI systems extract the first sentence or two to judge relevance.
• Support claims with cited statistics roughly every 150 to 200 words.
• Apply the right schema: Article for posts, FAQPage for FAQs, HowTo for steps, Organization and Person for entity clarity, and Product or Service on offering pages.
• Define your terms clearly and build topical authority so the entity behind your brand is unambiguous.

6. Conversion

Speed and findability are wasted if the page does not convert. A slow LCP and a sluggish INP both cost conversions, and layout shift erodes trust at exactly the moment a visitor is deciding to act. Check that your primary call to action renders fast, sits above the fold on mobile and is reachable by keyboard, that forms load quickly and validate clearly, and that nothing important depends on a script that arrives late.

When to get it done for you

You can run a first pass yourself with the free Google tooling above, and you should. The work gets harder when you move from finding problems to fixing them: diagnosing why INP fails on a specific template, reworking render-blocking code, doing genuine manual accessibility testing, and retrofitting schema and AEO structure across a large site. That is engineering, not a settings change.

SpotDev is a UK HubSpot Diamond Partner with an in-house engineering team. We are HubSpot Custom Integration Accredited and Onboarding Accredited, hold Cyber Essentials Plus, and back delivery with a guarantee: delivered on time, or you get 20% back. Our fixed-scope website audit covers Core Web Vitals, technical SEO, WCAG 2.2 AA accessibility, AEO and conversion in one report, with prioritised fixes and indicative effort, from £2,500. If you would rather have us build or rebuild the site properly, see our HubSpot websites service, or request a quote.

Frequently asked questions

What is a website performance audit?

A website performance audit is a structured review of how fast, stable, accessible, findable and persuasive your site is for real visitors and for the search and AI systems that rank and cite it. A thorough 2026 audit covers six layers: Core Web Vitals, site speed, technical SEO, WCAG 2.2 AA accessibility, answer engine optimisation and conversion. The output is a prioritised list of failures to fix, ordered by impact on traffic and revenue.

What are the Core Web Vitals thresholds in 2026?

Google's official thresholds are unchanged in 2026: Largest Contentful Paint of 2.5 seconds or less, Interaction to Next Paint of 200 milliseconds or less, and Cumulative Layout Shift of 0.1 or less. Each is measured at the 75th percentile of real-user page views, so a page passes only when at least 75% of visits hit the good threshold. INP replaced First Input Delay in March 2024 and is the metric most sites fail.

Do I need to meet WCAG 2.2 AA, or is 2.1 enough?

WCAG 2.2 AA is the current W3C recommendation and the sensible target for new and rebuilt sites. Legally, most current regulations still reference 2.1 AA, including the EU harmonised standard and the US DOJ Title II rule, with compliance dates running into 2027 and 2028. Building to 2.2 AA now is best practice and future-proofing. Because automated tools catch only around 57% of issues, meeting AA properly also requires manual keyboard and screen-reader testing.

What is the difference between SEO and AEO?

SEO works at page level, optimising titles, keywords, structure and links so search engines rank your pages. AEO, or answer engine optimisation, works at fact level, making your content easy for AI systems such as Google AI Overviews, ChatGPT, Perplexity and Claude to interpret, trust and cite. In practice you need both: lead sections with a direct 40 to 60 word answer, support claims with cited statistics, and apply the right schema so the entity behind your brand is clear.

How much does a professional website performance audit cost?

Costs vary with the size and complexity of the site, but a fixed-scope professional audit covering Core Web Vitals, technical SEO, accessibility, AEO and conversion typically starts from around £2,500. SpotDev's website audit delivers a prioritised report with indicative fix effort at that level. If the audit uncovers work that warrants a rebuild, indicative HubSpot website build pricing runs from roughly £15,000 to £80,000 depending on templates, custom code, integrations and migration complexity.