Web App Performance
A slow web app loses users before it even loads.
Web App Performance That Converts
Core Web Vitals affect search rankings, user retention, and conversion. We systematically analyse your web app's performance, identify the bottlenecks with the greatest impact, and optimise deliberately – delivering measurable improvements in LCP, CLS, and INP.
The essentials of Web App Performance
- We systematically analyse your web app's performance, identify the bottlenecks with the greatest impact, and deliberately optimise LCP, CLS, and INP.
- We measure before optimising – on real devices under real network conditions, not on a fast developer machine – and prioritise based on data, not assumptions.
- We optimise toward the Core Web Vitals (LCP under 2.5s, CLS under 0.1, INP under 200ms) because they measure what the user feels – not just a good Lighthouse score in the lab.
- The biggest lever is JavaScript: code-splitting loads only the current screen's code and moves non-critical work off the main thread, alongside bundle, rendering, and asset optimisation.
- With performance budgets and automated measurements we anchor the results so a hard-won value does not slip back at the next release.
Core Web Vitals
LCP (Largest Contentful Paint), CLS (Cumulative Layout Shift), and INP (Interaction to Next Paint) are Google's central web performance metrics. We measure them on real devices and in real network conditions – not just in a Lighthouse report under lab conditions – and optimise based on actual user data.
Bundle Optimisation
Oversized JavaScript bundles are the most common cause of slow web apps. We analyse bundle sizes, identify unnecessary dependencies, implement code splitting and lazy loading, and ensure only the code actually required for the current screen is loaded.
Rendering Strategies
Server-side rendering, static site generation, or client-side rendering – the rendering strategy directly impacts LCP and time-to-interactive. We select or recommend the appropriate strategy per content type and requirement, and combine strategies for optimal results.
Asset Optimisation
Images, fonts, and static assets are often unoptimised and slow the initial load considerably. Modern image formats, lazy loading, optimal caching, and font loading strategies that prevent layout shift – we optimise the entire asset stack.
Approach: measure, prioritise, optimise, guard
Web app performance improves through structure, not guesswork: first understand what is truly slowing things down, then act precisely and protect the gains long-term.
Profiling on real devices
Measurement under real network and CPU conditions – not on the developer's machine. Lighthouse, WebPageTest, Chrome DevTools, field data from CrUX.
Bottleneck analysis & prioritisation
Where is the greatest impact on LCP, INP, and CLS? Identify critical render and main-thread blocks – ranked by effort vs. effect.
Targeted optimisation
Code splitting, lazy loading, rendering strategy, asset compression, font and image optimisation – only what the profiling identified as a lever.
Performance budget & monitoring
Automated measurements in the CI/CD pipeline, per-route performance budgets – so a hard-won score does not silently regress on the next release.
Each phase builds on the findings of the previous one.
Where the levers actually are
Not every optimisation has the same effect. This relative weighting shows where effort makes the biggest difference for Core Web Vitals – especially on low-end mobile devices.
- JavaScript reduction & code splittingBiggest lever for Time-to-Interactive and INP on mobile CPU
- Main-thread reliefReduce long tasks; defer non-critical work (defer/idle)
- Rendering strategy (SSR/SSG/Hybrid)Determines when the first visible content appears (LCP)
- Image optimisation & modern formatsWebP/AVIF, responsive srcset, lazy loading – useful, rarely the sole bottleneck
- Fonts (FOUT, font-display, subsetting)Avoid CLS from layout shift; preload critical fonts
- Caching & CDN configurationAccelerate returning visits; long-lived caching for static assets
Relative weighting
Values show relative impact on Core Web Vitals, not absolute measurements.
What matters for Web App Performance
What matters in web app performance is measuring before optimising, and doing it on real devices under real network conditions. Profiling on a fast developer machine masks exactly the bottlenecks that slow an average mobile device. We prioritise on the basis of data, because the optimisation you intuitively suspect is often not the one with the biggest effect.
The Core Web Vitals are the right targets because they measure what the user feels. LCP concerns the first visible impression, CLS the annoying jumping layouts, INP the perceived response to input. Optimising for these real field values is something different from achieving a good Lighthouse score under lab conditions.
The biggest lever almost always lies with the JavaScript loaded and executed initially. Code-splitting so that only the current screen's code arrives, and moving non-critical work off the main thread, are what truly lower time-to-interactive on weak CPUs. Images and fonts are rewarding to optimise but rarely the actual brake.
And performance is not a one-off project but a property that decays again without a guard. Every new dependency and every unchecked feature can clog the main thread again. We anchor performance budgets and automated measurements so a hard-won value does not quietly slip back at the next release.
Measure Before Optimising
Without profiling on real devices in real network conditions, performance optimisation is guesswork. We begin every optimisation with structured measurement – and prioritise based on data, not assumptions.
Core Web Vitals as Target
LCP under 2.5 seconds, CLS under 0.1, and INP under 200ms are Google's thresholds for 'Good'. We optimise toward these values – not just a good Lighthouse score under lab conditions.
Code Splitting as Standard
Modern web app development requires code splitting: only the code needed for the current screen is loaded initially. This reduces time-to-interactive significantly – especially on mobile devices with weaker CPUs.
Fast on every device
With us you're always one step ahead technologically and tap directly into our extensive app development expertise. We take a close look at your app idea, identify key success factors and create tailor-made applications. Your visions and goals are at the heart of our joint project work.
Expert knowledge in app technologies
React Native, Flutter, native iOS and Android: we pick the stack to fit your project, not our preference.
Comprehensive user experience know-how
Intuitive operation and seamless interactions decide ratings and how long users stay in the app.
Proven track record
Published apps in the App Store and Play Store, from MVP to mature platform.
Versatile team
Concept, design, development and backend come together in one team that works without interface friction.
Long-term partnerships
We stay after launch and keep evolving your app with maintenance and updates.
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