
DebugBear
GTmetrix
SpeedCurve
PageSpeed Insights
WebPagetest
Pingdom
Request Metrics
Proxyman.io
CoreDash.app
SpeedCurve
Request Metrics
Core Web Vitals History
Lighthouse Metrics
Website and Application Performance Monitoring
Monitor the performance of your website and benchmark against the competition. Get alerted in Slack or by email when there's a problem.
Continuously test the speed of your website in a controlled lab environment and get in-depth reports to optimize your site. DebugBear is built on top of Lighthouse, but provides debug data that goes far beyond the basic Lighthouse report.
In addition to the lab data, DebugBear also keeps track of the real-user data collected by Google.
CoreDash is a Real User Monitoring platform built for Core Web Vitals.
The product is shaped around LCP, CLS, and INP. Those are the metrics that move search rankings and conversion rates, so they get the full attention of the dashboard, the alerts, and the API.
You install a lightweight script. CoreDash collects performance data from real visitors on real devices and real networks. The dashboard shows you what is slow, where, and for whom. Segment by page template, country, device class, connection type, or any custom dimension you add. Compare two date ranges to spot regressions the day they ship instead of the week they tank your CrUX scores.
The MCP server is the part most other RUM tools cannot match. It exposes your RUM data to AI agents through the Model Context Protocol. Claude, ChatGPT, or any agent that speaks MCP can query your field data and help you diagnose issues in plain English. Ask why LCP regressed on the product detail template last week. The agent reads the data and tells you.
Privacy is built in. Data is stored in the EU. The script runs without consent banners. Visitors stay anonymous by default.
A sub tool called Investigations blends RUM field data with Chrome lab diagnostics into a session first diagnostic experience. CLS before and after screenshot overlays show exactly which element shifted and what it looked like before.
CoreDash is built by Arjen Karel, an independent Core Web Vitals consultant with 17 years of experience. The same tool powers performance audits for eBay, Zalando, Nestlรฉ, Adevinta, DPG Media, and Harvard.
Paid plans start at $19 per month.
DebugBear
CoreDash.appNo features have been listed yet.
CoreDash.app's answer:
CoreDash is a Real User Monitoring platform with element level attribution for every Core Web Vital and a built in MCP server that lets Claude, Cursor, Windsurf, and other AI agents query your field data through the Model Context Protocol. Ask why LCP is slow on mobile in Germany and the agent reads your real user data, pinpoints the bottleneck phase, and names the responsible element. Most RUM tools show averages or sparklines. CoreDash shows you the exact CSS selector, the exact phase (TTFB, LOADDELAY, LOADTIME, RENDERDELAY for LCP; INPUTDELAY, PROCESSING, PRESENTATION for INP), and the exact Long Animation Frame causing INP regressions. Data is stored in the EU and the script runs without consent banners.
CoreDash.app's answer:
Three reasons. First, depth of attribution. Every metric drills down to the exact element and phase causing the slowdown, not just a number on a dashboard. Second, the MCP server. AI assistants like Claude and Cursor can query your real user data directly through the Model Context Protocol, so debugging a CWV regression becomes a plain English conversation with an agent that actually reads the data. Third, price. Paid plans start at $19 per month. SpeedCurve and New Relic Browser run into the hundreds or thousands per month for similar coverage. Privacy is also built in. Data is stored in the EU, no consent banner is needed, and visitors stay anonymous by default.
CoreDash.app's answer:
Frontend engineers, performance engineers, and technical SEO teams who own Core Web Vitals at sites that need real evidence from real users rather than synthetic lab numbers. Heavy use among teams shipping ecommerce, news, publishing, and content sites where CWV moves search rankings and conversion. Also popular with web performance consultants and agencies who need to show clients exactly which element is hurting their scores. The MCP integration draws an additional audience of AI native developers who run their performance investigations from inside Claude, Cursor, or Windsurf instead of clicking through dashboards.
CoreDash.app's answer:
CoreDash was built by Arjen Karel, an independent Core Web Vitals and PageSpeed consultant based in the Netherlands with 17 years of web performance experience. He has optimized over 925,000 mobile URLs and audits performance for eBay, Zalando, Nestlรฉ, Adevinta, DPG Media, and Harvard. Existing RUM tools were either too expensive, too shallow on attribution, or hid the field data behind dashboards that did not surface the actual cause of a regression. He built CoreDash as the tool he wanted to use himself, then opened it to other developers when they kept asking for access. The MCP server was added in 2025 once it became clear that performance debugging through AI agents was about to become the new normal.
CoreDash.app's answer:
A lightweight browser script using the Performance Observer API to capture LCP, INP, CLS, FCP, and TTFB with full attribution. The script also records element selectors for LCP and CLS, and Long Animation Frames (LoAF) so INP root causes can be traced to the exact long task and script. Beacons are sent to a high throughput backend pipeline with EU data storage. The dashboard is a modern web application. The MCP server speaks the Model Context Protocol so any compliant AI agent (Claude, Cursor, Windsurf, ChatGPT) can query field data programmatically. The CWV Insights MCP and a Core Web Vitals Visualizer Chrome extension are open source. The core platform is closed source.
CoreDash.app's answer:
CoreDash is built and used by Arjen Karel for performance consulting work, and the same tool powers audits and ongoing Core Web Vitals monitoring across major sites:
eBay Zalando Nestlรฉ Adevinta DPG Media Harvard
Not all of these are direct paying customers of the platform yet (the SaaS product is recent), but the engine has been running against their sites under Arjen's consulting work and informs every product decision.
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