Interactive
Free Performance Tools
Interactive calculators and analyzers to help you set performance targets, understand your scores, and prioritize optimizations. No signup required -- everything runs in your browser.
Performance Budget Calculator
Set your Core Web Vitals targets and connection speed. Get recommended budgets for JavaScript, CSS, images, and fonts -- plus framework compatibility analysis.
Open tool →Core Web Vitals Score Explainer
Enter your PageSpeed Insights scores to get a detailed explanation of what they mean, how you compare to benchmarks, and a prioritized list of fixes.
Open tool →Why use these tools?
Performance optimization starts with understanding your numbers. These tools bridge the gap between raw PageSpeed Insights data and actionable improvements.
- 01 Set realistic targets. The Performance Budget Calculator gives you concrete resource limits based on your speed goals and your users' connection profiles.
- 02 Understand your scores. The CWV Score Explainer translates metric values into plain-English assessments with framework-specific fix recommendations.
- 03 Prioritize fixes. Both tools help you focus on the changes that will have the greatest impact, so you do not waste time on marginal optimizations.
How to use these tools
Both calculators are deliberately small and opinionated. They are not replacements for PageSpeed Insights, the Chrome User Experience Report, or a paid Real User Monitoring product. They are designed for the moment in your day when you have a number in front of you (a budget, a score, a gut feeling) and need a clear next action without booting up a vendor dashboard.
Use the Performance Budget Calculator at the start of a project, or whenever leadership asks for a target. Pick a connection profile that matches your audience, choose what kind of LCP and TTFB you want to ship, and the tool returns a per-resource budget you can paste into a Lighthouse CI config or a webpack-bundle-analyzer threshold. Treat the numbers as a ceiling, not a floor: shipping a page under budget is the win, hitting it exactly is a warning.
Use the Core Web Vitals Score Explainer after a PageSpeed Insights run, especially when LCP and CLS disagree about whether the page is healthy. The explainer interprets each metric in context (does a 2.6s LCP matter if your CLS is zero?), then maps the worst metric to a short list of framework-specific fix pages. It is the fastest way to translate a yellow score into a one-paragraph engineering ticket.
What we are working on next
The tools section is the youngest part of the site, and we expand it as patterns emerge from the blog and fix library. Open candidates include a CrUX history viewer, a third-party script audit checklist that imports a HAR file, an INP attribution decoder, and a font-loading simulator that previews CLS for any font pair before you commit to a stylesheet.
Every tool here ships as a static HTML page with vanilla JavaScript so it loads fast and works offline. Nothing is sent to a server, nothing is stored, and the source is open. If you want to suggest a tool or report a bug, the GitHub repository is the canonical place to file an issue.
Continue learning
Frequently asked
Common questions
No. Every tool on this site runs entirely in the browser. Inputs are not transmitted to a server, and no analytics events are attached to tool interactions. The only network traffic generated by the tools page is the standard Vercel Web Analytics ping, which records page views but no event data.
Yes. Every tool is open source under the MIT license, with source available in the public repository. Pull requests for new tools or improvements to existing tools are welcomed; the contribute page documents the review process.
Lighthouse and PageSpeed Insights are full audit suites: they run a wide range of checks and produce a single overall score. The tools on this site are focused single-purpose utilities -- a budget calculator, a threshold checker, a CrUX query helper -- designed for the case where you already know what you are measuring and want a quick lab-side answer without going through a full audit run.