Two Point Five

Freelance Performance Marketeer

Kemari

Head of Marketing

Performance marketeer

Wemessage

Digital marketeer

Elevar BV

Junior Video Creative

Afstudeerstudent Marketing Automation

Huiskes-Kokkeler Autogroep

Stagiair Marketing

SES Creative

Productiemedewerker

C1000 Wesselerbrink

Verkoopmedewerker

Beschikbaar als freelance performance marketeer.

𝐇𝐨𝐞 𝐢𝐤 𝐦𝐞𝐫𝐤𝐞𝐧 𝐡𝐞𝐥𝐩
Advertising – Google Ads, Bing Ads, Meta
Data & tracking – Analytics, GTM, dashboarding, Server-side tracking
Conversieratio optimalisatie
Audits

𝐎𝐯𝐞𝐫 𝐦𝐢𝐣
Ik beschrijf mezelf graag als een technisch onderlegde en resultaatgerichte marketeer met een passie voor data. Mijn kracht ligt in het aanpakken van complexe situaties en deze terug te brengen tot een heldere, simpele en rechtdoorzee aanpak. Het realiseren van jouw bedrijfsdoelstellingen door middel van concrete plannen, prognoses en uiteindelijke marketing resultaten, dat is wat mij drijft.

Renaldo Spin

Core/Dash

CoreDash is dedicated to making the internet a faster and more eco-friendly place. CoreDash provides budget-friendly realtime RUM monitoring

Managing Director

MarketingTracer

Founder of MarketingTracer

Eigenaar

KRL Media

DPG Media Nederland

Web Performance Engeneer

International Association of Applied Psychology

Advising and implementing online strategy for international testing guidelines

Information Technology Project Consultant

Erasmus University

Building a complete e-learning enviroment for students

Project Manager

Most large websites are slow because their architecture is flawed. I show companies how to fix the root cause.

My name is Arjen Karel. I don't use guesswork; I use my own RUM platform, @Core/Dash, to get a precise, data-driven diagnosis of where your platform is failing its users. Then, I architect the solution.

This isn't about minor tweaks. It's about applying a level of architectural expertise your team doesn't have.

THE STANDARD
For a large-scale platform, Core Vitals aren't goals. They are architectural requirements.

• LCP: Content must render instantly. My architecture ensures it does.
• INP: The UI must be immediately responsive. My solutions eliminate input lag.
• CLS: The layout must be absolutely stable. I direct the engineering to enforce it.

Anything less is an architectural failure.

THE RESULT
The business result is obvious. A technically superior site ranks higher, converts better, and generates more revenue. This isn't a debate; it's a fact. My work delivers the architectural roadmap to achieve that.

ENGAGING WITH ME
I solve expensive problems for serious businesses. If that's you, get in touch. If not, don't.

Arjen Karel

Today, during a technical hike, I slipped off a rock and landed in freezing water. Pretty scary stuff. I was out of cell reception, a 2 hour hike back to the nearest town (if you could call it that).

But this is the stuff I live for. I never take the safe road and never look for the easy way. I look for challenges, something that motivates me physically or mentally.

But I am not a fool. I come prepared. I wanted to take this hike for weeks but I decided against it. It was just too dangerous. I also packed backup clothes in a dry-bag and a satellite rescue device.

On the way back, soaking wet and freezing, I was thinking... I just can't help it. This is just me, personally and professionally and I would not want it any other way.

I say no to most of the easy Core Web Vitals requests. Anyone can optimize a WordPress site. I don’t want those. I am looking for the one site no one has been able to figure out. I’m looking for the project that defines a year.

If you have the site that everyone else has given up on, that’s the one I want.

#CoreWebVitals #WebPerformance #TechnicalSEO #EngineeringLeadership #HighPerformance

Independent Web Performance Consultant. I fix “impossible” Core Web Vitals issues for Enterprise.

Want to build faster websites? Here is a simple audit technique I use daily:

JavaScript is slow. Use it only to enhance the webpage, but never depend on scripting for important parts of your page.

Use the "Disable JavaScript" feature in my Chrome extension during audits. Here is why it is powerful:
✅ Disables JavaScript execution 
✅ Bypasses <noscript> fallbacks 
✅ Reveals true dependencies you might miss otherwise

Now anything that is JavaScript related will just not appear on the page. That means you cannot hide your JavaScript dependency anymore by relying on noscript tags.

Try this in your next audit. You might be surprised what you find.

#CoreWebVitals #WebPerformance #JavaScript #WebDev #TechnicalSEO

Today is a massive milestone. My passion project, the Core Web Vitals Visualizer, just reached 12,000 active users.

I built this tool because I needed immediate, real-time data for my own client audits. I wanted to see the metrics right there on the page, not buried in logs.
To celebrate 12k users, I’ve pushed a major update:

🔎 The New Audit Tab: This automates some of the the manual checks I do during every audit. It breaks down typography loading behavior, validates image strategies, and instantly flags blocking resources, SPOF, node depth, hidden nodes, resource hints and more.

🧪 Revamped Experiments Tab: Experiments are now faster and cleaner. You can modify page behavior on the fly to temporarily remove known performance bottlenecks. My favorite addition is the "Third Party Kill Switch." I expected this feature to be an engineering headache, but it turned out to be a lightweight solution using a strict Content Security Policy (CSP).

Thank you to the 12,000 developers who trust this tool. If you want to build faster websites without the guessing game, give it a try.

(Link in the first comment!) 👇

#webperformance #corewebvitals #frontenddeveloper #chromeextension #javascript

"Hey Arjen, can we bring our AI note-taker to our meeting?"

​As someone who spends his weeks advising on pagespeed and technical issues this trend is becoming more and more visible.

​Whenever someone brings an AI note-taker to the call, the team is likely the least effective group I meet with this week.

That is why I am considering changing my answer to 'No, lets have a proper conversation and I'll send you the summary'. What do you think?

My shortest meetings happen at 09:00 AM.

Me: Is the RUM snippet gathering data? 
Client: No, we had holidays and got busy. 
Me: Deploy it today. We will reconvene in seven days.

Performance engineering requires field data. I can audit the critical rendering path and profile the main thread, but without historical user data ... I cannot validate.

I refuse to optimize for a lighthouse score. I optimize for the p95 user experience. That requires data!

#webperformance #perfmatters #RUM #corewebvitals

taplio

The Battle

Renaldo Spin

Arjen Karel

Followers

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taplio

The Battle

Renaldo Spin

Arjen Karel

Followers

Posts

Engagements

Likes

Performance Score.css-goub6s{font-size:var(--chakra-fontSizes-md);font-weight:500;color:var(--chakra-colors-gray-600);display:block;margin-top:var(--chakra-space-1);}Arjen Karel's LinkedIn Performance

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Performance ScoreArjen Karel's LinkedIn Performance