Debug Bear
Website speed test and Core Web Vitals monitoring. Real browser testing.
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Use it free
Open the official tool or demo — no account needed.
Self-host it
Run the open-source version on your own infrastructure.
What is Debug Bear?
DebugBear is an open-source web performance monitoring tool designed to analyze and optimize website speed, with a focus on Google's Core Web Vitals. It helps developers, SEO specialists, and site owners identify performance bottlenecks that negatively impact user experience and search engine rankings. The tool addresses issues like slow page load times, poor interactivity, and unstable layout shifts by providing actionable insights and recommendations. By integrating synthetic monitoring with real-user data, DebugBear enables continuous performance tracking, ensuring websites meet modern SEO standards and deliver a browsing experience. Its emphasis on Core Web Vitals aligns with Google's ranking criteria, making it a critical tool for maintaining competitive online visibility.
How it works
DebugBear is a web performance analysis tool that combines synthetic monitoring with real-user data to assess website speed and Core Web Vitals. It provides detailed reports on page load times, resource loading sequences, and third-party script impacts. The tool is primarily used by developers and SEO professionals to diagnose performance issues, optimize user experience, and ensure compliance with Google's Core Web Vitals guidelines. It serves as a bridge between technical performance metrics and business outcomes like higher conversion rates and improved SEO rankings. DebugBear offers free website speed tests, synthetic monitoring from 30+ locations, and real-user performance data via Google CrUX. It identifies slow pages, highlights third-party code delays, and provides step-by-step load analysis. Integration with tools like CircleCI allows automated Lighthouse score tracking and page weight monitoring.
How to use it
- 1Visit DebugBear's website and enter the URL of the site to test. 2. Select test locations (e.g., Mobile + US East) for synthetic monitoring. 3. Run the performance analysis to generate a detailed report. 4. Review Core Web Vitals scores, load timelines, and optimization suggestions. Practical tips include using the free trial for initial assessments, prioritizing high-traffic pages for optimization, and monitoring changes over time to track improvements.
What it can do
- Utility
Use cases
Assumptions and limitations
Assumptions
- source: https://github.com/debugbear
- license: Open source
- privacy: Opens an external demo
Limitations
- The free tier offers basic synthetic monitoring without advanced analytics or historical data tracking
- Limited support for custom metrics beyond Core Web Vitals and Lighthouse scores
- Dependence on third-party services like Google CrUX may introduce data latency or availability issues
- Manual intervention required for complex optimizations beyond automated recommendations
- No built-in tools for A/B testing or real-time user behavior analysis
Understanding the result
Website speed test and Core Web Vitals monitoring. Real browser testing.
Tool details
- Clearly flagged when a network request is needed.
- No account, no sign-up, and no tracking of your content.
- Powered by debugbear (MIT).
- Built with
- debugbear (https://github.com/debugbear)
- License
- MIT
- Runs locally
- No — requires a network request
- Verification
- Not yet verified
- Input
- Text
- Output
- Output
Built with https://github.com/debugbear. OpenToolVault provides the discovery and browser interface while crediting the original project maintainers.
- Built with
- debugbear
- License
- MIT
Open-source project
OpenToolVault is an independent directory. We are not affiliated with or endorsed by this project.
References
- /debugbear — GitHub Repository
Upstream project · GitHub
Frequently asked
What does DebugBear's free tier include?
The free tier allows basic website speed tests, synthetic monitoring from 30+ locations, and real-user performance data via Google CrUX. Users can identify slow pages, analyze load timelines, and receive optimization recommendations. However, advanced features like historical data tracking and automated CI/CD integrations require a paid subscription.
How does DebugBear integrate with development workflows?
DebugBear connects with tools like CircleCI to automate Lighthouse score tracking and page weight monitoring. Developers can configure CI/CD pipelines to run performance checks on code changes, ensuring new updates don't degrade site speed. The GitHub repository also provides examples for bulk Lighthouse testing and integration with netlify-build-plugin-debugbear for deployment pipelines.
How do I interpret DebugBear's Core Web Vital reports?
DebugBear's reports display Lighthouse scores, load times, and visual metrics like Largest Contentful Paint (LCP), First Input Delay (FID), and Cumulative Layout Shift (CLS). Users can drill into load timelines to see which resources delay performance, with specific recommendations like optimizing images or deferring non-critical scripts. The Google CrUX data provides real-user insights into how the site performs for actual visitors.
How does DebugBear compare to tools like Lighthouse or PageSpeed Insights?
DebugBear focuses on continuous monitoring and real-user data via Google CrUX, while Lighthouse provides lab-based audits and PageSpeed Insights offers general performance suggestions. DebugBear's synthetic monitoring from multiple locations complements Lighthouse's detailed technical analysis, and its integration with CI/CD pipelines sets it apart from standalone tools like PageSpeed Insights.
What should I do if DebugBear's test fails to load a website?
If a test fails, ensure the website is accessible via the tested URL and not blocked by CORS or robots.txt rules. Check for JavaScript errors that might prevent the tool from executing properly. If the issue persists, try alternative test locations or contact DebugBear's support for troubleshooting. GitHub repository errors suggest clearing browser cache or reloading the page may resolve temporary loading issues.