38 website testing and optimisation resources
Improve loading time, accessibility, SEO, security and more with these excellent website testing and optimisation resources.
GO/NO-GO
Be sure you're ready to launch with this collection of site checking tools with one-click links.
Responsive Image Breakpoints Generator
Easily generate the optimal responsive image dimensions. One image for all screen resolutions and different devices is not enough. An image per pixel is too...
Cypress
Fast, easy and reliable testing for anything that runs in a browser.
Bundlephobia
Find the cost of adding a npm package to your bundle. JavaScript bloat is more real today than it ever was. Sites continuously get bigger as more (often...
Lightning-Fast Web Performance
A free online lecture course by Scott Jehl. Learn to analyze site performance, fix issues, monitor for regressions, and deliver fast, responsive designs from...
Shift Nudge UI Checklist
101 UI Checklist items available as a free Notion template.
CSS Stats
CSS Stats provides analytics and visualizations for your stylesheets. This information can be used to improve consistency in your design, track performance of...
Who Can Use Colour Checker
A fantastic colour contrast checker tool that brings attention to how color contrast can affect different people with visual impairments using statistics and...
PageReview
Visual feedback tool directly on live websites.
Reflect Automated Testing
Automated regression tests without a line of code.
Axe Accessibility Testing
Robus accessibility testing browser extension.
Checka11y.css
A CSS stylesheet to quickly highlight a11y concerns.
Can I use
Interactive browser support tables for HTML, CSS and other browser features.
BlurHash
BlurHash takes an image and gives you a short string that represents the placeholder for an image for a more seamless loading experience.
Stark
Integrated suite of tools for accessibility compliance testing in Figma, Sketch and XD.
Color Blind Filter
View your website with simulated colour blindness to ensure your content is accessible.
Website Launch Checklist
Launch your next web project with complete confidence!
Fathom Analytics
Fathom is a simple, light-weight, privacy-first alternative to Google Analytics. So, stop scrolling through pages of reports and collecting gobs of personal...
Polypane
Develop, debug and test websites and apps twice as fast. Know for sure your sites and apps work everywhere and for everyone.
Screen Size Map
An interactive map of screen sizes for responsive and adaptive design.
Jpeg.io
Convert any major image format into a highly optimized JPEG.
ImageOptim
ImageOptim makes images load faster. Removes bloated metadata. Saves disk space & bandwidth by compressing images without losing quality.
Squoosh
Squoosh is an image compression web app that allows you to dive into the advanced options provided by various image compressors.
Meta Tags
Meta Tags is a tool to debug and generate meta tag code for any website. With Meta Tags you can edit and experiment with your content then preview how your...
WebPageTest
Run a free website speed test from multiple locations around the globe using real browsers (IE and Chrome) and at real consumer connection speeds. You can run...
CodeFactor
Automated code review for Git.
GeoScreenshot
GeoScreenshot is a convenient tool to preview how your webpage looks in multiple locations.
web.dev
Get the web's modern capabilities on your own sites and apps with useful guidance and analysis from web.dev.
SEO Analyzer
If you’re struggling to get more visitors to your site, the answer might just lie in this free report!
tota11y
An accessibility visualization toolkit. tota11y helps visualize how your site performs with assistive technologies.
Contrast Ratio
A tool to calculate the contrast ratio between any two valid CSS colors.
Low Vision
Test your website with simulated vision impairments.
Nibbler
Nibbler is a free tool for testing websites. Enter the address of any website and Nibbler will give you a report scoring the website out of 10 for key areas,...
Alix for Chrome
Alix allows you to lint your HTML for Accessibility issues simply by applying a stylesheet that makes use of advanced CSS selectors.
A11y Command-line Tools
Web accessibility audits powered by the Chrome logo Chrome Accessibility Developer Tools.
Browserling
Live interactive cross-browser testing. Get started in less than 5 seconds. Test in IE11 for free or upgrade for more options.
BuiltWith
Web technology information profiler tool. Find out what a website is built with.
Google Mobile Speed Test
Test your mobile site speed in realistic conditions and receive actionable recommendations using this handy Google utility.
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