A performance budget is a contract with your user: your site will load in under X seconds, on Y connection, on Z device. Here is how we set and hold ours.
Every site we build has a performance budget. It is one of the first documents we create and one of the last things we check before launch. Most agencies do not use them. This is a significant reason why most websites are slow — and slow websites are quietly destroying business results for thousands of companies who have no idea why their bounce rate is high.
What a performance budget actually is
A performance budget is a set of limits on the technical characteristics of a webpage that directly affect load speed and user experience. Typical metrics we budget for: Total page weight (our standard maximum is 1.5MB for initial load), Time to First Contentful Paint (target under 1.5 seconds), Largest Contentful Paint (target under 2.5 seconds), Total Blocking Time (target under 200ms), and Cumulative Layout Shift (target under 0.1). These are not arbitrary numbers — they are the thresholds Google uses in Core Web Vitals to determine search ranking.
Why most sites blow past these limits
The culprits are almost always the same: uncompressed images (the single biggest offender), unoptimised third-party scripts (analytics, chat widgets, ad pixels), render-blocking JavaScript, and excessive font loading. We have audited sites with a single hero image weighing 14MB. We have seen sites loading 47 third-party scripts on every page. These are not edge cases — they are the norm.
How we enforce the budget
We run Lighthouse audits at every major development milestone, not just at launch. We use Next.js Image component for automatic image optimisation and WebP conversion. We audit every third-party script before adding it and require justification for anything that adds more than 50KB. We test on throttled connections (simulating 3G) on every device breakpoint. The result: every site we ship scores 90+ on all Core Web Vitals.
What this means for your business
Google has explicitly confirmed that Core Web Vitals are a ranking signal. A site that loads in 1.5 seconds will rank better than an identical site that loads in 4 seconds, all else being equal. More importantly, every additional second of load time reduces conversion rate by approximately 7%, according to multiple large-scale studies. Performance is not a technical nicety. It is a revenue lever.
Let us put these ideas into practice for your brand.