checks.md

Check reference

Every check, grouped by area. The severity shown is the default for the check, and a finding can carry a lower one. A rule of thumb is a practical guide for a threshold, not a standard.

SEO

Id	Severity	Check	Why it matters	How to fix	Rule of thumb
SEO-TITLE-001	error	Page has no title	The title is the main heading shown in search results and browser tabs. Without one, search engines pick their own text.	Add a unique <title> that describes the page in about 50 to 60 characters.	None
SEO-TITLE-002	info	Title is very short or very long	Very short titles say little about the page. Search results cut long titles off, so the end may never be seen.	Aim for a title between 10 and 60 characters that puts the main words first.	Fails below 10 or above 60 characters. Search results truncate by pixel width, so 60 characters is a rule of thumb.
SEO-TITLE-003	warning	Title is shared with other pages	Pages with the same title are hard to tell apart in search results and in browser tabs.	Give each page its own title that describes what is unique about it.	None
SEO-TITLE-004	warning	Page has more than one title	Browsers and search engines have to choose between the titles, and they may choose the wrong one.	Keep a single <title> element in the document head and remove the rest.	None
SEO-DESC-010	warning	Page has no meta description	Search engines often use the meta description as the snippet under the title. Without one they choose text from the page.	Add a <meta name="description"> that summarises the page in one or two sentences.	None
SEO-DESC-011	info	Meta description is very short or very long	A very short description gives searchers little reason to click. Search results cut long descriptions off.	Write a description between 50 and 160 characters that says what the page offers.	Fails below 50 or above 160 characters. Snippet length varies by device and query, so 160 characters is a rule of thumb.
SEO-DESC-012	warning	Meta description is shared with other pages	Identical descriptions make different pages look the same in search results.	Write a description for each page that reflects its own content.	None
SEO-H1-020	warning	Page has no h1 heading	The h1 tells readers and search engines what the page is about.	Add one <h1> that states the topic of the page.	None
SEO-H1-021	info	Page has more than one h1 heading	HTML allows more than one h1, but a single one keeps the page outline clear for readers and search engines.	Use one <h1> for the page topic and <h2> or lower for sections.	None
SEO-CANON-030	warning	Page has no canonical link	A canonical link tells search engines which URL to index when the same content is reachable at several addresses.	Add <link rel="canonical"> pointing at the preferred URL of the page, usually the page itself.	None
SEO-CANON-031	error	Page has conflicting canonical links	When the canonical links disagree, search engines may ignore them and choose for themselves.	Keep one canonical link per page. Check whether a plugin or theme adds a second one.	None
SEO-CANON-032	error	Canonical points to a broken or redirecting URL	A canonical that does not return a normal page sends search engines to a dead end, so the page may drop out of the index.	Point the canonical at the final URL of a page that returns status 200.	None
SEO-CANON-033	warning	Canonical points to a different origin	A canonical on another host or scheme asks search engines to index that other site instead of this page.	Use a canonical on the same scheme and host as the page, unless the move is intended.	None
SEO-INDEX-040	info	Page is set to noindex	Search engines will not list a noindex page. This is listed so you can confirm it is intended.	If the page should appear in search, remove the noindex directive from the meta robots tag and the X-Robots-Tag header.	None
SEO-INDEX-041	error	A noindex page is listed in the sitemap	The sitemap says the page should be indexed while the page says it should not, so the two signals contradict each other.	Remove the page from the sitemap, or remove the noindex directive.	None
SEO-INDEX-042	error	A sitemap URL is blocked by robots.txt	The sitemap offers a URL that robots.txt forbids crawlers to fetch. Search engines cannot read a page they may not crawl.	Remove the URL from the sitemap, or change the robots.txt rule that blocks it.	None
SEO-INDEX-043	error	The start page is set to noindex	A noindex start page keeps the home of the site out of search results.	Remove the noindex directive from the start page meta robots tag and X-Robots-Tag header.	None
SEO-LANG-050	warning	Page has no lang attribute	The lang attribute tells browsers, search engines and screen readers which language the page is in.	Add a lang attribute to the <html> element, for example <html lang="en">.	None
SEO-VIEW-051	error	Page has no viewport meta tag	Without a viewport tag, phones show the page zoomed out as a desktop layout, which is hard to read and use.	Add <meta name="viewport" content="width=device-width, initial-scale=1"> to the head.	None
SEO-OG-060	info	Open Graph tags are missing	Open Graph tags control the title, text and image shown when the page is shared on social networks and in chat apps.	Add og:title, og:description and og:image meta tags to the head.	None
SEO-LD-070	warning	Structured data is not valid JSON	Search engines skip a JSON-LD block they cannot parse, so the page loses any rich results it was meant to earn.	Fix the syntax of the JSON-LD block. A JSON validator will point at the error.	None
SEO-ROBOTS-080	warning	No robots.txt file	Crawlers look for robots.txt first. Without one they assume everything may be crawled and they cannot find the sitemap from it.	Publish a robots.txt at the root of the site, even a short one that links to the sitemap.	None
SEO-ROBOTS-081	error	robots.txt blocks the whole site	It tells search engine crawlers not to fetch any page of the site.	Remove the Disallow: / rule for the all-crawlers group, unless the site is meant to stay private.	None
SEO-ROBOTS-082	error	robots.txt returns a server error	When robots.txt answers with a server error, search engines may stop crawling the site until it recovers.	Make robots.txt answer with status 200, or status 404 if you have none. Check the server logs for the error.	None
SEO-MAP-090	warning	No sitemap found	A sitemap helps search engines find every page, especially new pages and pages with few links to them.	Publish a sitemap.xml and list it in robots.txt.	None
SEO-MAP-091	info	robots.txt does not reference the sitemap	A Sitemap line in robots.txt lets every crawler find the sitemap without being told about it.	Add a line such as Sitemap: https://example.com/sitemap.xml to robots.txt.	None
SEO-MAP-092	error	A sitemap URL does not return status 200	The sitemap should list only live pages. Broken or redirecting entries waste crawl effort.	Remove the URL from the sitemap, or list its final address.	None
SEO-MAP-093	error	A sitemap file could not be parsed	Search engines ignore a sitemap they cannot read, so none of its URLs are submitted.	Check that the file is valid sitemap XML and is served with status 200.	None
SEO-MAP-094	info	A sitemap URL is not linked from any crawled page	A page that nothing links to is hard for visitors and crawlers to reach. It may be an orphan.	Link the page from a relevant page or the navigation, or remove it from the sitemap if it is retired.	Only evaluated when the crawl was not cut short, because an uncrawled page might hold the missing link.
SEO-THIN-100	info	Page has little text	Pages with very little text give search engines little to rank. Some pages, such as contact or gallery pages, are fine this way.	If the page should rank, add useful text that answers what visitors come for.	Fails below 150 words of visible text. This is a rule of thumb and may be fine for contact or gallery pages.

Health

Id	Severity	Check	Why it matters	How to fix	Rule of thumb
HEALTH-LINK-001	error	Broken internal link	Visitors and search engines who follow the link reach an error page instead of content.	Fix the link to point at a working page, or restore the missing page and redirect it if it moved.	A link whose target answered 429 or 503 during the audit is reported as not verified, because the answer says nothing about whether the page exists.
HEALTH-LINK-002	warning	Internal link points at a redirect	Each redirect adds a round trip for visitors and crawlers.	Update the link to point straight at the final address.	None
HEALTH-REDIR-010	warning	Redirect chain has more than one hop	Every extra hop slows the page down and gives crawlers another chance to give up.	Redirect the first address straight to the final address.	None
HEALTH-REDIR-011	error	Redirect loop or too many redirects	Browsers and crawlers give up on a loop, so the page cannot be reached at all.	Remove the redirect that points back at an earlier address in the chain.	Fails on a loop, or on a chain of more than 10 hops, which the crawler stops following.
HEALTH-HTTPS-020	error	HTTP is not upgraded to HTTPS	Plain HTTP traffic can be read and changed on the way, and browsers label such sites as not secure.	Install a certificate, serve the site over HTTPS, and redirect every HTTP address to its HTTPS version.	None
HEALTH-HTTPS-021	error	Mixed content on an HTTPS page	Browsers block or warn about resources loaded over HTTP on a secure page, so the page can look broken.	Change the resource addresses to HTTPS, or remove them.	None
HEALTH-HTTPS-022	warning	HTTPS page links to an internal page over HTTP	Visitors who follow the link leave the secure version of the site and may hit an extra redirect.	Change the link to use https://.	None
HEALTH-HOST-023	warning	www and apex hosts both answer without a redirect	Two hosts serving the same site can split links and ranking signals between them, and create duplicate pages.	Pick one host as the main one and redirect the other to it.	None
HEALTH-404-030	warning	Missing pages return 200 (soft 404)	Search engines may index error pages as real content, and broken links are harder to find.	Make the server return status 404 for addresses that do not exist.	None
HEALTH-FAV-040	info	No favicon	Browsers ask for a favicon to show in tabs and bookmarks. Without one they show a generic icon, and the requests end in 404 errors.	Add a favicon link to the page head, or serve a file at /favicon.ico.	None
HEALTH-HDR-050	warning	No Strict-Transport-Security header	Without this header, browsers may still try plain HTTP first, which leaves a window for downgrade attacks.	Send Strict-Transport-Security with a max-age of at least six months on every HTTPS response.	None
HEALTH-HDR-051	info	No Content-Security-Policy header	A content security policy limits where scripts and other resources can load from, which reduces the damage of injected code.	Add a Content-Security-Policy header. Start in report-only mode if the site loads many third-party resources.	None
HEALTH-HDR-052	warning	No X-Content-Type-Options nosniff header	Without nosniff, some browsers guess file types and may run a file as a script when it was not meant to be one.	Send X-Content-Type-Options: nosniff on every response.	None
HEALTH-HDR-053	info	No Referrer-Policy header	Without a policy, browsers decide how much of the page address is shared with other sites when a visitor clicks a link.	Send a Referrer-Policy header such as strict-origin-when-cross-origin.	None
HEALTH-HDR-054	info	No clickjacking protection	Without X-Frame-Options or a frame-ancestors rule, other sites can embed the page in a frame and trick visitors into clicking hidden controls.	Send X-Frame-Options or add a frame-ancestors rule to the Content-Security-Policy.	None
HEALTH-EXT-060	warning	Broken external link	Links that lead nowhere frustrate visitors and make the site look neglected.	Update or remove the link.	Statuses 401, 403, 405, 429 and 503, and any status outside 100 to 599, are reported as could not verify (info), because many sites refuse automated requests.
HEALTH-FETCH-070	warning	Page timed out or was cut short	The audit only saw part of the page, and slow pages are also slow for visitors and crawlers.	Check the server for slow responses, and reduce the page size if it hit the size cap.	None

Performance

Id	Severity	Check	Why it matters	How to fix	Rule of thumb
PERF-RESP-001	warning	Slow server response	A slow first response delays everything that follows, and visitors notice.	Look at server work before the HTML is sent: slow queries, missing page caching, or an underpowered host.	Fails above 800 ms. This is one measurement from the auditing machine, so treat it as a guide and not a benchmark.
PERF-HTML-010	warning	HTML document is very large	Large documents take longer to download and parse, especially on slow mobile connections.	Remove inline data and repeated markup, and load long lists in parts.	Fails above 500 KB (500000 bytes) of decoded HTML. A rule of thumb, not a hard limit.
PERF-COMP-020	error	HTML is served without compression	Compression usually cuts the size of HTML by a large share, so pages download faster.	Turn on gzip or Brotli compression for HTML responses in the web server or CDN.	Only documents over 1 KB (1024 bytes) are checked, because compressing tiny files gains little.
PERF-COMP-021	warning	Script or stylesheet served without compression	Text assets compress well. Sending them as they are wastes bandwidth and slows rendering.	Turn on gzip or Brotli compression for JavaScript and CSS files.	Only files over 1 KB (1024 bytes) are checked.
PERF-CACHE-030	warning	Static asset is not cached for long	Without a cache lifetime, returning visitors download the same files again on every visit.	Send Cache-Control with a max-age of at least one hour, and a year for files whose names change when they change.	Fails when there is no max-age and no Expires, when max-age is under 3600 seconds, or on no-store. Only measured assets on the audited origin are checked.
PERF-WEIGHT-040	warning	Page is heavy	Heavy pages load slowly on mobile connections and use up visitors' data.	Compress and resize images first, then remove scripts and fonts the page does not need.	Fails above 2 MB (2000000 bytes) and up to 5 MB, counting the HTML and the assets that were measured. Assets that were not measured are not counted, and the finding says how many.
PERF-WEIGHT-041	error	Page is very heavy	Pages this large take a long time to load on slow connections and use a lot of mobile data.	Compress and resize images first, then remove scripts and fonts the page does not need.	Fails above 5 MB (5000000 bytes), counting the HTML and the assets that were measured. This replaces the 2 MB warning for the same page.
PERF-REQ-042	info	Page references many resources	Each script, stylesheet and image is another request, which adds delay on slow connections.	Combine small files, drop unused ones, and lazy load images below the fold.	Fails above 80 unique scripts, stylesheets and images. A rule of thumb.
PERF-IMG-050	warning	Large image	Images are often the largest part of a page.	Resize the image to the size it is shown at and compress it, or use a modern format such as WebP or AVIF.	Fails above 300 KB (300000 bytes) and up to 1 MB. A rule of thumb.
PERF-IMG-051	error	Very large image	An image this large can take seconds to load and uses a lot of mobile data.	Resize the image to the size it is shown at and compress it, or use a modern format such as WebP or AVIF.	Fails above 1 MB (1000000 bytes). This replaces the 300 KB warning for the same image.
PERF-IMG-052	warning	Images without width and height	Without both attributes the browser cannot reserve space, so the page jumps as images load.	Add width and height attributes that match the image's own size, and let CSS scale it.	Decorative images are counted too, because layout shift applies to them as well.
PERF-IMG-053	info	Images below the fold are not lazy loaded	Images far down the page compete with the content visitors see first.	Add loading="lazy" to images that start below the first screen.	Counts images after the third in the document. Position in the document is a proxy for being below the fold.
PERF-IMG-054	info	Large JPEG or PNG	Modern formats such as WebP and AVIF are often smaller at the same quality.	Convert the image to WebP or AVIF, and keep the old format as a fallback only if needed.	Fails for JPEG and PNG files over 100 KB (100000 bytes). A modern format may be smaller, but not always.
PERF-BLOCK-060	warning	Render-blocking script in the head	A script in the head without async or defer stops the browser from showing the page until it has loaded and run.	Add defer, or async for independent scripts, or move the script to the end of the body.	None
PERF-BLOCK-061	info	Many stylesheets in the head	The browser waits for every stylesheet in the head before it draws the page.	Combine stylesheets, or inline the critical rules and load the rest later.	Fails above 4 stylesheets in the head. A rule of thumb.

Accessibility

Static checks only. This is not an accessibility audit: contrast, keyboard use, focus order and screen reader behaviour are not tested.

Id	Severity	Check	Why it matters	How to fix	Rule of thumb
A11Y-ALT-001	warning	Image without an alt attribute	Screen readers have nothing to say about an image with no alt attribute, and may read out the file name instead.	Add an alt attribute that describes the image. Use alt="" for images that are only decoration.	Images marked aria-hidden="true" or role="presentation" are not counted, because screen readers skip them.
A11Y-LABEL-010	warning	Form control without a label	People using screen readers cannot tell what a field is for, and a label also gives a larger target to click.	Add a label element that points at the field, or an aria-label or aria-labelledby attribute.	Hidden, submit, button, reset and image inputs are not counted. Image inputs need alt text instead.
A11Y-LINK-020	warning	Link without an accessible name	A link with no text, label or image alt is announced as just link, so people using screen readers cannot tell where it goes.	Add link text, or an aria-label, or alt text on the image inside the link.	None
A11Y-LINK-021	info	Generic link text	People who move through a page by its links hear them out of context, so click here and read more tell them nothing.	Write link text that says where the link goes or what it does.	Compares the link text, lower-cased and without trailing punctuation, with: "click here", "here", "read more", "more", "learn more", "link", "this".
A11Y-BTN-030	warning	Button without an accessible name	A button with no text or label is announced as just button, so people using screen readers cannot tell what it does.	Add text inside the button, or an aria-label.	None
A11Y-HEAD-040	info	Heading levels are skipped	People who move through a page by its headings expect the levels to nest, and a gap suggests missing content.	Use the next heading level down, and pick levels for structure and not for size.	Fails when a heading is more than one level deeper than the heading before it.
A11Y-FRAME-050	info	Iframe without a title	Screen readers announce an iframe by its title, so without one people cannot tell what the embedded content is.	Add a short title attribute that says what the frame contains.	None