A website can look perfectly healthy… while loading slowly, containing broken links, disappearing from search results or failing to record visits correctly. These website checking and optimisation tools can help you measure speed, improve images, investigate search visibility, understand visitor behaviour and identify technical, privacy or security problems. Many are free, although some require an account or offer additional paid features. Remember to test several representative pages (not just your homepage) and concentrate on useful improvements rather than chasing a perfect score.
Accessibility is an important part of website quality too. For accessibility checkers, screen readers and inclusive-technology resources, visit our Accessibility and Inclusive Technology page.
Updated September 2026.
Jump to: Speed, Images and Sustainability, SEO & Search Visibility, Links Code and Site History, Analytics & Visitor Behaviour, Privacy, Security & Reliability
Quick Picks
| I want to… | Quick pick |
|---|---|
| Find out what is slowing down a webpage | Google PageSpeed Insights |
| Run a detailed performance test | GTmetrix |
| Compress a few images before uploading them | TinyPNG |
| Optimise WordPress images automatically | ShortPixel |
| Estimate a webpage’s environmental impact | Website Carbon Calculator |
| See how my website performs in Google Search | Google Search Console |
| Check my website’s visibility in Bing | Bing Webmaster Tools |
| Crawl a website for SEO and technical problems | Screaming Frog SEO Spider |
| Test structured data and rich-result eligibility | Google Rich Results Test |
| Find broken internal and external links | Online Broken Link Checker |
| Check the HTML used to build a page | W3C HTML Checker |
| View or save an earlier version of a webpage | Wayback Machine |
| Measure website visits and conversions | Google Analytics |
| See heatmaps and anonymised session recordings | Microsoft Clarity |
| View Google information inside WordPress | Site Kit by Google |
| Troubleshoot Google Analytics and advertising tags | Google Tag Assistant |
| Find cookies and trackers used by a website | Cookiebot Website Cookie Checker |
| Examine website security headers | MDN HTTP Observatory |
| Check a website’s HTTPS configuration | Qualys SSL Labs |
| Receive an alert when a website stops responding | UptimeRobot |
Speed, Images & Sustainability
Google PageSpeed Insights
Google PageSpeed Insights tests the performance of an individual webpage on mobile and desktop devices. It reports Core Web Vitals and other performance measurements, highlights possible causes of slow loading and suggests improvements involving images, scripts, fonts, caching and page layout.
Best for: Finding performance problems on an individual webpage
Cost: Free
Works on: Web browsers
Worth knowing: Where sufficient information is available, the report includes data from real Chrome users as well as a simulated laboratory test. Scores can vary between tests, so concentrate on recurring problems rather than repeatedly testing until you receive a higher number.
Visit Google PageSpeed Insights
GTmetrix
GTmetrix measures how quickly a webpage loads and provides a visual report showing its size, requests, performance measurements and loading sequence. Its waterfall chart can help identify large images, scripts, fonts or third-party services that are delaying a page.
Best for: Investigating how individual files and services affect page speed
Cost: Limited free plan; paid Pro plans available
Works on: Web browsers
Worth knowing: Results depend on the test location, device and connection being simulated. Some mobile testing, monitoring, locations and report-history features require a paid account.
TinyPNG
TinyPNG compresses AVIF, WebP, PNG and JPEG images so that they take up less space and load more quickly online. Upload an image, allow the service to optimise it and then download the smaller version ready to add to a website.
Best for: Quickly compressing images before uploading them
Cost: Free for up to 20 images at a time, with a 5 MB limit per image; paid web and developer plans available
Works on: Web browsers; a WordPress plugin and developer API are also available
Worth knowing: TinyPNG uses lossy compression, which permanently removes some image information. The difference is often difficult to see, but check photographs containing fine detail and graphics containing small text before replacing the originals.
ShortPixel Image Optimizer
ShortPixel is a WordPress image-optimisation plugin that can automatically compress photographs and graphics as they are uploaded. It can also resize large images and create modern WebP and AVIF versions, reducing the amount of information visitors must download.
Best for: Automatically optimising a WordPress media library
Cost: Free for up to 100 credits each month; paid monthly and one-off credit plans available
Works on: WordPress websites; separate browser tools and a macOS application are also available
Worth knowing: WordPress can create several thumbnail sizes from one uploaded image, and each optimised thumbnail may use a credit. Back up your website and test the compression settings before processing a large existing media library.
Website Carbon Calculator
Website Carbon Calculator estimates the carbon emissions associated with loading a webpage. Its calculation considers factors including the amount of data transferred and whether the website appears to use verified green hosting, then gives the page a rating and comparison.
Best for: Starting a conversation about lighter and more sustainable website design
Cost: Free
Works on: Web browsers
Worth knowing: The result is an estimate for one page load rather than a direct measurement of an entire website. Use it to compare pages and identify opportunities to reduce unnecessary images, video, scripts and other downloaded data.
Visit Website Carbon Calculator
SEO & Search Visibility
Google Search Console
Google Search Console shows how Google discovers, indexes and displays a website. Its reports can reveal the searches that cause pages to appear, clicks from Google, indexing problems, Core Web Vitals, external links and security or manual-action warnings.
Best for: Monitoring and improving a website’s presence in Google Search
Cost: Free
Works on: Web browsers
Worth knowing: You must verify that you own or manage the website. Search Console reports Google Search information rather than every source of website traffic, and some reports take time to update.
Bing Webmaster Tools
Bing Webmaster Tools helps website owners understand how their pages perform in Bing search results. It includes search-performance information, URL inspection, sitemap submission, keyword research, backlink data and a Site Scan that checks for common technical SEO problems.
Best for: Checking indexing and search visibility beyond Google
Cost: Free
Works on: Web browsers
Worth knowing: You must verify ownership of the website, although existing Google Search Console properties can usually be imported. Its reports describe Bing’s view of your site and may differ from Google’s findings.
Screaming Frog SEO Spider
Screaming Frog SEO Spider crawls a website in a similar way to a search engine. It can identify broken links, redirects, duplicate or missing page titles, absent headings, oversized images, canonical-address problems and many other technical SEO issues.
Best for: Carrying out a detailed technical crawl of a small or medium-sized website
Cost: Free for crawls of up to 500 URLs; paid annual licence for larger crawls and advanced features
Works on: Windows, macOS and Linux
Worth knowing: The amount of information can initially feel overwhelming. Start with response codes, page titles, meta descriptions and headings before moving into the more technical reports.
Visit Screaming Frog SEO Spider
Google Rich Results Test
Google Rich Results Test checks the structured data attached to a webpage or pasted into the tool. It identifies valid items, errors and warnings and shows whether the page may be eligible for enhanced Google results such as event, course, product or breadcrumb information.
Best for: Testing schema and structured data added by a website or SEO plugin
Cost: Free
Works on: Web browsers
Worth knowing: A valid result means that the structured data is technically eligible; it does not guarantee that Google will display an enhanced result. The information on the page must also follow Google’s content and quality guidelines.
Visit Google Rich Results Test
Links, Code & Site History
Online Broken Link Checker
Online Broken Link Checker scans a website for links that no longer work. It checks links to pages within the website as well as links leading elsewhere and reports the page containing each problem and the relevant response code.
Best for: Finding broken links without installing software
Cost: Free for websites containing up to 3,000 pages
Works on: Web browsers
Worth knowing: A reported problem can occasionally be caused by a temporary outage, security protection or a website blocking automated checks. Test an affected link yourself before removing or changing it.
Visit Online Broken Link Checker
W3C HTML Checker
The W3C HTML Checker examines the code used to build a webpage and reports markup that does not follow current web standards. It can identify missing attributes, incorrectly nested elements, duplicate identifiers and other coding mistakes that may produce unpredictable results.
Best for: Checking HTML after adding custom code to a website
Cost: Free
Works on: Web browsers
Worth knowing: Some messages are technical, and WordPress themes or plugins may generate code that you cannot edit directly. A validation error does not automatically mean that visitors will see a problem, but it can provide a useful starting point for investigation.
Internet Archive Wayback Machine
The Wayback Machine stores historical snapshots of publicly available webpages. It can help you see how a page previously looked, recover wording or information from a deleted page and investigate the history of a website. Its Save Page Now feature can also request a snapshot of a public page.
Best for: Viewing or preserving a public version of a webpage
Cost: Free
Works on: Web browsers
Worth knowing: The Wayback Machine is not a replacement for a proper website backup. Some images, downloads, interactive features and pages protected by a login may not have been captured.
Analytics & Visitor Behaviour
Google Analytics
Google Analytics collects information about visits to a website or app. Its reports can show where visitors came from, which pages they viewed, the devices they used and whether they completed important actions such as submitting a form, making a purchase or booking a course.
Best for: Measuring website traffic, marketing campaigns and conversions
Cost: Free standard service; paid Analytics 360 edition for large organisations
Works on: Most websites and apps; reports are viewed through a web browser or mobile app
Worth knowing: Analytics needs to be configured correctly before useful information is collected, and it cannot recreate data from before tracking was installed. Review your privacy notice, retention settings and consent configuration before collecting visitor information.
Microsoft Clarity
Microsoft Clarity uses heatmaps and session recordings to show how visitors interact with a website. It can reveal where people click, how far they scroll and whether they repeatedly select something that does not work as expected.
Best for: Understanding how visitors actually use individual webpages
Cost: Free
Works on: Most websites; reports are viewed through a web browser
Worth knowing: Session recordings and heatmaps need careful privacy configuration. Ensure that sensitive information is masked and that your privacy and consent arrangements explain the service appropriately.
Site Kit by Google
Site Kit is Google’s official WordPress plugin for connecting and displaying information from services including Search Console, Analytics and PageSpeed Insights. It places useful summaries inside the WordPress dashboard and can simplify the initial connection process without requiring code editing.
Best for: Viewing important Google information from inside WordPress
Cost: Free and open source
Works on: Self-hosted WordPress websites
Worth knowing: A WordPress administrator must complete the setup and authorise access to the relevant Google services. Site Kit displays selected information, but the full Google services still provide more detailed reports and settings.
Google Tag Assistant
Google Tag Assistant helps check whether Google Analytics, Google Ads and Google Tag Manager tags are installed and working. Its debugging session shows the tags, events and information being sent as someone moves between pages and performs actions on a website.
Best for: Troubleshooting missing or inaccurate Google tracking data
Cost: Free
Works on: Google Chrome and the web-based Tag Assistant service
Worth knowing: Tag Assistant checks Google tags rather than every analytics or advertising service. The results are fairly technical, but they can help a website developer determine whether a problem lies with the tracking code or the reporting configuration.
Privacy, Security & Reliability
Cookiebot Website Cookie Checker
Cookiebot’s online scanner checks a website for cookies and tracking technologies and produces a report describing what it finds. The wider Cookiebot consent-management service can categorise cookies, display a consent banner and control non-essential tracking according to a visitor’s choices.
Best for: Discovering cookies and trackers that may have been added by plugins or external services
Cost: Free website scan and free plan for one small website; paid plans available
Works on: Public websites and web browsers; integrations are available for several website platforms
Worth knowing: A clean scan does not prove that a website meets every legal requirement. Check that each service is described accurately in your privacy and cookie information and obtain professional advice where necessary.
Visit Cookiebot Website Cookie Checker
MDN HTTP Observatory
MDN HTTP Observatory, originally developed by Mozilla, examines the security-related HTTP headers and other configuration information returned by a website. It provides a score and grade and links to explanations of protections such as Content Security Policy and Strict-Transport-Security.
Best for: Identifying missing or weak website security headers
Cost: Free
Works on: Public websites and web browsers
Worth knowing: Adding or changing security headers incorrectly can stop fonts, videos, forms or scripts from working. Discuss unfamiliar recommendations with your hosting provider or developer and test the website carefully after making changes.
Qualys SSL Labs Server Test
Qualys SSL Labs performs a detailed check of the HTTPS and TLS configuration used by a public website. It examines the security certificate, supported protocols and server settings and gives each tested server a grade.
Best for: Checking the quality of a website’s HTTPS configuration
Cost: Free
Works on: Public websites and web browsers
Worth knowing: The report is technical and may identify changes that need to be made by your hosting company rather than in WordPress. Select the option not to display results on the public boards if you do not want the test listed.
UptimeRobot
UptimeRobot checks a website at regular intervals and sends an alert if it stops responding. It can also record incidents and response times, helping website owners discover outages that occur when they are not personally visiting the site.
Best for: Receiving an early warning that a website is unavailable
Cost: Free for up to 50 monitors with five-minute checks; paid plans add faster checks and advanced features
Works on: Web browsers, iOS and Android
Worth knowing: The free plan may take several minutes to detect a short outage. Uptime monitoring confirms whether the website responds; it does not prove that every page, form or booking process is functioning correctly.
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Note: please read the disclaimer before downloading/using any of the web & social tools and software.