About PerfDelta

PerfDelta is a free page speed test that measures several pages of a website in one run. The report puts the Core Web Vitals of real Chrome users next to the lab metrics of a Lighthouse run and compares them with the global benchmark and, if you like, with your competitors. Every report gets its own link to share.

Christian Schreiber, founder of PerfDelta

I started writing software at twelve and building websites at 14. I monetized those early sites as an affiliate publisher, and because they needed reach, I got into search engine optimization early on. I eventually sold my first bigger affiliate site to an online shop.

I studied business information systems in Flensburg, Germany, and did my internship and my thesis at an agency in Hamburg, where I deepened my SEO knowledge and built up hands-on experience in paid search. After that I worked as an SEO consultant in Berlin. Alongside that, I built a web portal of my own and ran it with a business partner for eight years. So I know the site owner's side well: you need the traffic, and you are the one who has to ship the fixes.

Since 2013 I've been a managing partner at digitalagenten GmbH, a digital agency in Berlin, where I advise companies on SEO strategy and web performance, as well as marketing automation and AI.

PageSpeed Insights is the standard tool for speed checks, but it measures one URL at one point in time. I built PerfDelta for the questions that come next: how does the site compare with its competitors, and how do the numbers change over time? So the test measures several pages at once and puts them next to your competitors' field data, and monitoring then tracks the numbers over weeks and months.

I develop the tool and the measurement method myself and I'm responsible for the guides on this site. Every month I also measure larger lists of websites, which feed the website speed statistics and the industry benchmarks.

The most interesting delta is the one between your site and your fastest competitor's.

Profiles: LinkedIn · Xing

Data sources: PageSpeed Insights API and Chrome UX Report

Lab metrics come from the Google PageSpeed Insights API, field data from the Chrome UX Report. PerfDelta uses the same public interfaces as PageSpeed Insights. The optimization notes in a report are phrased by a Mistral AI language model, based on the measured values and the detected technology stack. How pages are selected, which thresholds apply and how the benchmarks are calculated is described on the methodology page.

Privacy: no account needed, reports deleted after 365 days

A test needs nothing but a public URL. No account and no email address are required. The report, including the screenshots, is deleted automatically after 365 days. Details are in the privacy policy.

Guides: fixing Core Web Vitals and Lighthouse warnings

The guides explain the Core Web Vitals and the individual metrics such as LCP and INP. Others cover the most common PageSpeed and Lighthouse warnings, such as render-blocking resources or unused JavaScript.

Each guide walks through the fix step by step, with code examples, common mistakes and a way to verify that the fix worked. Many include notes for WordPress and Shopify. A data block adds current figures from PerfDelta's own measurements, recalculated daily.

Plans: Core Web Vitals monitoring with history and alerts

The test stays free. If you want to keep an eye on your numbers over time, Core Web Vitals monitoring is available in three paid plans: Solo, Agency and Scale. They measure your URLs automatically, daily or weekly on Solo and as often as every six hours on Agency and Scale. They also pull Chrome UX Report field data every day and send an email alert when a metric gets worse. On top of that you get a weekly performance report, the full report history, PDF export and MCP access, so AI agents can start measurements and read results.

Agency and Scale are built for agencies and teams with several sites. They add white-label PDFs for clients, CSV export, a public status dashboard, the REST API, industry benchmark data and multiple team seats. Prices and limits per plan are on the pricing page.

Contact: questions and feedback about PerfDelta

Questions, feedback or ideas for the tool: use the contact form or write to me at [email protected].