Datart.cz Test Results
Datart.cz Mobile Performance: 30/100
Quick overview:
Opportunities
These suggestions can help your page load faster. They don't directly affect the Performance score.
Preload key requests. Potential savings of 5,760 ms
Consider using `<link rel=preload>` to prioritize fetching resources that are currently requested later in page load. Learn more.
Serve images in next-gen formats. Potential savings of 629 KiB
Image formats like JPEG 2000, JPEG XR, and WebP often provide better compression than PNG or JPEG, which means faster downloads and less data consumption. Learn more.
Properly size images. Potential savings of 502 KiB
Serve images that are appropriately-sized to save cellular data and improve load time. Learn more.
Efficiently encode images. Potential savings of 438 KiB
Optimized images load faster and consume less cellular data. Learn more.
Eliminate render-blocking resources. Potential savings of 1,880 ms
Resources are blocking the first paint of your page. Consider delivering critical JS/CSS inline and deferring all non-critical JS/styles. Learn more.
Avoid multiple page redirects. Potential savings of 1,410 ms
Redirects introduce additional delays before the page can be loaded. Learn more.
Remove unused JavaScript. Potential savings of 376 KiB
Remove unused JavaScript to reduce bytes consumed by network activity. Learn more.
Remove unused CSS. Potential savings of 91 KiB
Remove dead rules from stylesheets and defer the loading of CSS not used for above-the-fold content to reduce unnecessary bytes consumed by network activity. Learn more.
Minify CSS. Potential savings of 18 KiB
Minifying CSS files can reduce network payload sizes. Learn more.
Avoid serving legacy JavaScript to modern browsers. Potential savings of 56 KiB
Polyfills and transforms enable legacy browsers to use new JavaScript features. However, many aren't necessary for modern browsers. For your bundled JavaScript, adopt a modern script deployment strategy using module/nomodule feature detection to reduce the amount of code shipped to modern browsers, while retaining support for legacy browsers. Learn More
Enable text compression. Potential savings of 40 KiB
Text-based resources should be served with compression (gzip, deflate or brotli) to minimize total network bytes. Learn more.
Minify JavaScript. Potential savings of 36 KiB
Minifying JavaScript files can reduce payload sizes and script parse time. Learn more.
Diagnostics
More information about the performance of your application. These numbers don't directly affect the Performance score.
Does not use passive listeners to improve scrolling performance
Consider marking your touch and wheel event listeners as `passive` to improve your page's scroll performance. Learn more.
Ensure text remains visible during webfont load
Leverage the font-display CSS feature to ensure text is user-visible while webfonts are loading. Learn more.
Avoid `document.write()`
For users on slow connections, external scripts dynamically injected via `document.write()` can delay page load by tens of seconds. Learn more.
Avoid an excessive DOM size
6,915 elements
A large DOM will increase memory usage, cause longer style calculations, and produce costly layout reflows. Learn more.
Reduce the impact of third-party code
Third-party code blocked the main thread for 960 ms
Third-party code can significantly impact load performance. Limit the number of redundant third-party providers and try to load third-party code after your page has primarily finished loading. Learn more.
Minimize main-thread work
7.7 s
Consider reducing the time spent parsing, compiling and executing JS. You may find delivering smaller JS payloads helps with this. Learn more
Serve static assets with an efficient cache policy
79 resources found
A long cache lifetime can speed up repeat visits to your page. Learn more.
Reduce JavaScript execution time
2.2 s
Consider reducing the time spent parsing, compiling, and executing JS. You may find delivering smaller JS payloads helps with this. Learn more.
Avoid large layout shifts
5 elements found
These DOM elements contribute most to the CLS of the page.
Avoid long main-thread tasks
20 long tasks found
Lists the longest tasks on the main thread, useful for identifying worst contributors to input delay. Learn more
Avoid chaining critical requests
11 chains found
The Critical Request Chains below show you what resources are loaded with a high priority. Consider reducing the length of chains, reducing the download size of resources, or deferring the download of unnecessary resources to improve page load. Learn more.
Keep request counts low and transfer sizes small
115 requests • 1,951 KiB
To set budgets for the quantity and size of page resources, add a budget.json file. Learn more.
Largest Contentful Paint element
1 element found
This is the largest contentful element painted within the viewport. Learn More
Datart.cz Mobile SEO: 84/100
Quick overview:
Mobile Friendly
Make sure your pages are mobile friendly so users don’t have to pinch or zoom in order to read the content pages. Learn more.
Tap targets are not sized appropriately
97% appropriately sized tap targets
Interactive elements like buttons and links should be large enough (48x48px), and have enough space around them, to be easy enough to tap without overlapping onto other elements. Learn more.
Content Best Practices
Format your HTML in a way that enables crawlers to better understand your app’s content.
Image elements do not have `[alt]` attributes
Informative elements should aim for short, descriptive alternate text. Decorative elements can be ignored with an empty alt attribute. Learn more.
Crawling and Indexing
To appear in search results, crawlers need access to your app.
Links are not crawlable
Search engines may use `href` attributes on links to crawl websites. Ensure that the `href` attribute of anchor elements links to an appropriate destination, so more pages of the site can be discovered. Learn More
Datart.cz Mobile Best Practices: 71/100
Quick overview:
Trust and Safety
Does not use HTTPS
1 insecure request found
All sites should be protected with HTTPS, even ones that don't handle sensitive data. This includes avoiding mixed content, where some resources are loaded over HTTP despite the initial request being servedover HTTPS. HTTPS prevents intruders from tampering with or passively listening in on the communications between your app and your users, and is a prerequisite for HTTP/2 and many new web platform APIs. Learn more.
Includes front-end JavaScript libraries with known security vulnerabilities
9 vulnerabilities detected
Some third-party scripts may contain known security vulnerabilities that are easily identified and exploited by attackers. Learn more.
General
Registers an `unload` listener
The `unload` event does not fire reliably and listening for it can prevent browser optimizations like the Back-Forward Cache. Consider using the `pagehide` or `visibilitychange` events instead. Learn More
Browser errors were logged to the console
Errors logged to the console indicate unresolved problems. They can come from network request failures and other browser concerns. Learn more
Page has valid source maps
Source maps translate minified code to the original source code. This helps developers debug in production. In addition, Lighthouse is able to provide further insights. Consider deploying source maps to take advantage of these benefits. Learn more.
Datart.cz Mobile Progressive Web App: 25/100
Quick overview:
Fast and reliable
`start_url` does not respond with a 200 when offline
A service worker enables your web app to be reliable in unpredictable network conditions. Learn more. No usable web app manifest found on page.
Current page does not respond with a 200 when offline
If you're building a Progressive Web App, consider using a service worker so that your app can work offline. Learn more.
Page load is not fast enough on mobile networks
Interactive at 16.0 s
A fast page load over a cellular network ensures a good mobile user experience. Learn more. Your page loads too slowly and is not interactive within 10 seconds. Look at the opportunities and diagnostics in the "Performance" section to learn how to improve.
PWA Optimized
Does not set a theme color for the address bar.
The browser address bar can be themed to match your site. Learn more. Failures: No manifest was fetched,
No `<meta name="theme-color">` tag found.
Manifest doesn't have a maskable icon
A maskable icon ensures that the image fills the entire shape without being letterboxed when installing the app on a device. Learn more. No manifest was fetched
Is not configured for a custom splash screen
A themed splash screen ensures a high-quality experience when users launch your app from their homescreens. Learn more. Failures: No manifest was fetched.
Installable
Does not use HTTPS
1 insecure request found
All sites should be protected with HTTPS, even ones that don't handle sensitive data. This includes avoiding mixed content, where some resources are loaded over HTTP despite the initial request being servedover HTTPS. HTTPS prevents intruders from tampering with or passively listening in on the communications between your app and your users, and is a prerequisite for HTTP/2 and many new web platform APIs. Learn more.
Does not register a service worker that controls page and `start_url`
The service worker is the technology that enables your app to use many Progressive Web App features, such as offline, add to homescreen, and push notifications. Learn more.
Web app manifest does not meet the installability requirements
Browsers can proactively prompt users to add your app to their homescreen, which can lead to higher engagement. Learn more. Failures: No manifest was fetched.
Datart.cz Mobile Accessibility: 71/100
Quick overview:
ARIA
These are opportunities to improve the usage of ARIA in your application which may enhance the experience for users of assistive technology, like a screen reader.
`[aria-hidden="true"]` elements contain focusable descendents
Focusable descendents within an `aria-hidden="true"]` element prevent those interactive elements from being available to users of assistive technologies like screen readers. [Learn more.
ARIA input fields do not have accessible names
When an input field doesn't have an accessible name, screen readers announce it with a generic name, making it unusable for users who rely on screen readers. Learn more.
ARIA IDs are not unique
The value of an ARIA ID must be unique to prevent other instances from being overlooked by assistive technologies. Learn more.
Best practices
These items highlight common accessibility best practices.
The document uses `<meta http-equiv="refresh">`
Users do not expect a page to refresh automatically, and doing so will move focus back to the top of the page. This may create a frustrating or confusing experience. Learn more.
Contrast
These are opportunities to improve the legibility of your content.
Background and foreground colors do not have a sufficient contrast ratio.
Low-contrast text is difficult or impossible for many users to read. Learn more.
Names and labels
These are opportunities to improve the semantics of the controls in your application. This may enhance the experience for users of assistive technology, like a screen reader.
Image elements do not have `[alt]` attributes
Informative elements should aim for short, descriptive alternate text. Decorative elements can be ignored with an empty alt attribute. Learn more.
Buttons do not have an accessible name
When a button doesn't have an accessible name, screen readers announce it as "button", making it unusable for users who rely on screen readers. Learn more.
Links do not have a discernible name
Link text (and alternate text for images, when used as links) that is discernible, unique, and focusable improves the navigation experience for screen reader users. Learn more.
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