Signs Your Website Is Slow and What To Fix First

Most teams know speed matters, right up until deadlines pile up and a quick image upload casually adds 3MB to the homepage. If you are hearing complaints from sales about the site feeling heavy, you probably do not need another sermon. You need a fast way to confirm the problem and a sensible order of fixes that will not blow up your roadmap.This guide shows how to spot the signs your website is slow, how to prove it with real data, and what to fix first. We focus on Core Web Vitals, the clearest connection between speed, user experience and search visibility described in Google’s Core Web Vitals guidance.

Key takeaways

• Use Core Web Vitals to validate signs your website is slow.
• Prioritise LCP, INP and CLS changes that affect users first.
• Compress and properly size hero media before anything else.
• Cut long JavaScript tasks to reduce input delays on mobile.
• Reserve space for images, ads and embeds to prevent layout shift.
• Track wins in CrUX over time, not just lab scores.

How to confirm your website is slow before you panic

Start by validating, not guessing. Largest Contentful Paint measures how quickly the main content appears, Interaction to Next Paint measures how fast the page responds to input, and Cumulative Layout Shift captures how much the page jumps while it loads, with thresholds documented in Google’s Core Web Vitals guidance.

Use a mix of field and lab data. Field data reflects how real users experienced your pages and is available through the Chrome UX Report, which is the official dataset of the Web Vitals programme described in the CrUX documentation.

Lab data is produced in a controlled environment so you can debug quickly, and PageSpeed Insights explains how it blends Lighthouse diagnostics with CrUX field results in its About PageSpeed Insights page.

Context matters. The UK’s connectivity has improved, with Ofcom reporting average maximum download speeds up to 223Mbps in 2024 on the Connected Nations 2024 hub.

Field vs lab data explained in plain English

Field data answers the question, what did my users actually experience last month. It is great for executive conversations and tracking progress over time because it reflects real networks, devices and behaviour at the 75th percentile. Lab data answers, what is broken right now, and where do I start? It is fantastic for isolating render-blocking resources, long JavaScript tasks and layout shifts while a developer has the code open, and this explainer on lab and field differences shows why both are needed.

Common signs your website is slow that you can spot without tools

You can often see the symptoms before you measure them. If the hero section appears late or sits blank for a second or two, your LCP candidate is slow. Common culprits include an oversized hero image, a late-loading web font or an uncached HTML response. If buttons feel inert after the page looks ready, you are experiencing poor interactivity, usually from heavy JavaScript or a framework doing too much work before responding to input.

Layout jank is another dead giveaway. If content jumps as images, ads or embeds appear, you are burning user patience and increasing your CLS. Users perceive this as sloppy rather than slow, but the outcome is the same: they lose trust and bounce. If an off-canvas menu arrives half a beat late, or form fields shift as the cookie banner pops in, that is a layout shift problem masquerading as a UI quirk.

Mobile pain is louder. Watch for frustrated taps, especially on mid-range Android devices. If the checkout continue button ignores the first tap or a filter drawer stutters open, long tasks in your JavaScript thread are likely blocking input. Heavy libraries, unnecessary polyfills and unoptimised components add up quickly, particularly on list pages and product detail pages.

Behavioural clues in analytics & support tickets

Analytics patterns can rat you out. Rising mobile bounce on key landing pages, sessions with very short engagement time, and spikes in exit rate after interactive steps often point to performance bottlenecks. Support inboxes will echo it as the site is not working or the page will not load reports, especially around campaign launches when third-party tags multiply. If you have access to rage-click metrics or session replays, look for storms of clicks before navigation occurs. These are classic signs your website is slow to respond rather than slow to render.

What to fix first: a prioritised playbook

Speed work gets political fast, so you need a neutral, impact-first order of attack. The north star is improving Core Web Vitals for your most important templates on real devices. Prioritise the fixes that move LCP, INP and CLS, then follow with supporting work that compacts payloads and stops regressions.

Start with your most valuable pages: homepage hero, top product or service pages, and checkout or lead forms. Use PageSpeed Insights to capture both the field baseline and a lab run you can repeat during development, and remember that CrUX data is a rolling 28-day view, as explained in the CrUX API notes.

1) Make the main content render fast (LCP)

Identify the LCP element on each key template. It is usually a hero image, background image or heading. Compress and resize that media, and prefer modern formats such as AVIF or WebP. Defer non-critical CSS and inline just enough critical CSS for the above-the-fold region. Eliminate slow server responses with caching at the edge and enable HTTP/2 or HTTP/3 where supported.

If your HTML is dynamic, make sure you are caching fragments and using a CDN that can serve the first byte quickly. Preload the LCP asset so the browser does not wait to discover it, and avoid lazy-loading it by mistake. Large, late-loading fonts also delay text rendering, so use font-display: swap, subset your fonts and preload the primary weight used in the hero.

2) Cut delays to first interaction (INP)

Long tasks in JavaScript are the usual villains. Audit your bundle and remove what you can. Split code by route and component, and load non-essential features only after the first interaction. If you are using a heavy framework, prefer server components where possible, hydrate less on the client and schedule non-urgent work with requestIdleCallback.

Collapse third-party scripts ruthlessly. Marketing tags, chat widgets, A/B testing, analytics and social embeds each nibble at your thread time. Replace synchronous scripts, defer non-critical ones, and use a tag manager to control load conditions. Measure input delay directly on problematic templates, identify long tasks over 50ms, then break them apart.

3) Stop unexpected movement (CLS)

Reserve space for anything that might appear later. That means setting width and height on images, defining aspect ratios on video containers and allocating fixed slots for ad units and embeds. Avoid injecting banners at the top of the viewport; if you must show consent or promo banners, place them in reserved containers.

Preload your primary web font and use a fallback with similar metrics to reduce reflow when the custom font arrives. Audit any carousels, accordions and lazy-loading patterns for shift-inducing behaviour. Small fixes here produce an outsized perception gain because stability feels more professional to users than a raw millisecond win.

Supporting fixes that compound gains

Optimise images across the board with automated compression and responsive srcset sizes. Generate AVIF and WebP variants, but also cap dimensions sensibly. Deliver critical CSS inline and defer the rest. Remove unused CSS where possible. Preconnect and preload only where it helps discovery. Review third-party bloat quarterly and adopt hard budgets for total transfer size and script execution time, which aligns with the Web Almanac page weight findings.

Measuring progress and keeping it fast

Speed is a process, not a tidy one-off. Track improvements using field data so you can see percentile trends and seasonality rather than single test runs, and use the CrUX documentation to understand coverage.

If you need a quick visual for stakeholders, use PageSpeed Insights for per-URL snapshots and add release guardrails in your pipeline so regressions are caught before they ship, which the PSI documentation also supports with clear diagnostics.

Keep a quarterly review of third-party scripts, and treat any new tag the way you would treat a new SaaS contract: it pays rent in performance, or it gets evicted. Remember that connectivity is improving but uneven across the UK, as shown in Ofcom’s Connected Nations 2024 report.

Conclusion

The signs your website is slow are usually obvious to users and only slightly less obvious to teams staring at dashboards. Confirm the problem with Core Web Vitals, prioritise changes that improve LCP, INP and CLS on your most valuable pages, and measure in the field so the wins stick. Speed work compounds, which means a faster, more stable site converts better, costs less to operate and feels nicer to use.

If you want structured help with prioritisation, auditing and a roadmap that aligns with your goals, we can map a clear plan and hand it to your team to execute or deliver it for you.