Ep 6: Unattributed Navigation Overhead (UNO) and Tackling 3rd Party Challenges with Partytown
In this episode, Tim Vereecke introduces us to UNO, the missing link in any TTFB analysis. Then, Julian Jandl walks us through a case study on how to overcome third-party challenges in large enterprises using Partytown.
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The missing link: UNO
Meet UNO, the missing link in any TTFB analysis. Without Unattributed Navigation Overhead you are lost, because TTFB is rarely the sum of Redirect+DNS+TCP+TLS in the field! Understanding UNO has saved Tim countless hours in RUM.
In this talk, Tim will share RUM examples why understanding and measuring UNO is crucial in 2025.
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Peak Performance with Partytown - A case study
45% of all requests made by websites are third-party requests. A huge portion of them are scripts you cannot control, nor improve. They are competing with your application code about the priority on the main thread. Bloating the main thread with more execution than necessary ultimately screws the runtime performance and responsiveness of our applications - especially for mobile users.
In this talk, Julian is going to introduce you to partytown. A library that helps you to execute 3rd party scripts in a sandboxed worker thread - making use of true multi threading in the browser.
Julian Jandl is a Lead Performance Engineer, trainer, and consultant at Push-Based.io, where he helps companies build faster, more efficient web applications at scale. Passionate about web performance and modern frontend architecture, Julian spends his time diving deep into the browser’s internals, conducting real-world audits, eliminating bottlenecks, and delivering high-impact workshops on Angular and web performance. Whether it’s tuning milliseconds off load times or mentoring teams in hands-on sessions, Julian brings a practical approach to making the web fast.