De.serlo.org - SEO Checker

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Overview of the SEO Check
Meta information
79% 
Page quality
51% 
Page structure
100% 
Link structure
96% 
Server
97% 
External factors
100% 
SEO Score
Response time
0.46 s
File size
157.40 kB
Words
199
Media files
13
Number of links
41 internal / 6 external

Task list of SEO Improvements

Meta specifications

Title
(Critically important)
Serlo – Die freie Lernplattform
The length of the page title is perfect. (270 pixels out of 580 max pixel length)
There are no duplicate words in the title
Meta description
(Critically important)
The meta description is missing.
Crawlability
(Critically important)
There are no problems in accessing the website.
Canonical URL
(Important)
https://de.serlo.org/
There is a valid canonical link specified.
Language
(Somewhat important)
Language detected in text: de
Language defined in HTML: de
Server location: Canada
The following language is defined by HTML: de
Alternate/Hreflang Links
(Somewhat important)
There are no alternate links specified on this page.
Other meta tags
(Somewhat important)
There is no rel next meta tag on this page.
There is no rel prev meta tag on this page.
Domain
(Somewhat important)
This page is hosted on a subdomain. Use a top level domain for better SEO results.
The domain does not contain non-latin characters.
Page URL
(Somewhat important)
No parameters were found in the URL.
No session ID was found in the URL.
The URL does not have too many subdirectories.
Charset encoding
(Somewhat important)
The charset encoding (UTF-8) is set correctly.
Doctype
(Nice to have)
The doctype HTML 5 is set correctly.
The doctype is placed at first in the HTML code.
Favicon
(Nice to have)
The favicon is linked correctly.

Meta tags

NameValue
viewportwidth=device-width
imagehttps://de.serlo.org/_assets/img/meta/landing.png
next-head-count13
robotsmax-image-preview:large
msapplication-TileColor#007ec1
msapplication-config/_assets/browserconfig.xml
theme-color#007ec1
langde
og:site_nameSerlo
og:typewebsite
og:titleSerlo – Die freie Lernplattform
og:urlhttps://de.serlo.org/
og:descriptionDie freie Lernplattform
og:imagehttps://de.serlo.org/_assets/img/meta/landing.png
og:image:width1200
og:image:height630
charsetutf-8

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Page quality

Content
(Critically important)
There are only 199 words on this page. Use at least 250 words to provide useful information.
Words from the H1 heading are not used in the page content.
The average number of words per sentence of 9.17 words is low.
31.7% of the text are stop words.
Keywords used in the page title are also used in the page content. That's good!
The page contains a listing, which indicates a good text layout.
3 paragraphs were found on this page.
No placeholders texts or images were found.
There are no duplicates on the site.
Frames
(Critically important)
This page does not use a frameset.
Mobile optimization
(Somewhat important)
A viewport "width=device-width" is provided.
At least one Apple touch icon is specified.
Bold and strong tags
(Somewhat important)
The usage of strong and bold tags is perfect. We recommend the use of up to 6 tags for this page.
Image SEO
(Somewhat important)
1 images have no alt attribute. The content of alt attributes is used by search engines.
Social Networks
(Nice to have)
There are only a few social sharing widgets on the page. Make your website popular in social networks with social sharing widgets.
Additional markup
(Nice to have)
No additional page markup was found.
HTTPS
(Somewhat important)
This website uses HTTPS to protect privacy and integrity of the exchanged data.
All included files are also transferred via HTTPS.

Media list

URLAlt attributeTitle
/_assets/img/serlo-logo.svgSerlo
...rlo.org/avatar/Daniel-Flueck&w=3840&q=75Avatar von daniel-flueck
...3d03f7ba7812d2016a61ae61.jpg&w=3840&q=75Avatar von metzgaria
...rlo.org/avatar/WandaPaetzold&w=3840&q=75Avatar von wandapaetzold
...2995638232d83b0b608cb910.jpg&w=3840&q=75Avatar von nish
...aa307ba6674dba6a5e05776.jpeg&w=3840&q=75Avatar von karin
...3add676fa2893b34c5823fdb.jpg&w=3840&q=75Avatar von flora_jana
...a58ec4cb0c865d13451f45eb.jpg&w=3840&q=75Avatar von Leogato
...8ed4f41b527dcc1318651373.jpg&w=3840&q=75Avatar von kathongi
...eb8df6bf53a5628f7e2dbebf.jpg&w=3840&q=75Avatar von wo_fo
...ity.serlo.org/avatar/Corinna&w=3840&q=75Avatar von corinna
/_assets/img/landing/birds.svgNo alt attribute provided
...s/img/donations/partners.png&w=1920&q=75Partner und Förderer Logos

Page structure

H1 heading
(Critically important)
Was möchtest du lernen ?
The H1 heading is perfect.
Headings
(Important)
The heading structure is perfect.

Heading structure

Heading levelContent
H1 Was möchtest du lernen ?
H2 Mathematik
H2 Nachhaltigkeit
H2 Biologie
H2 Chemie
H2 Informatik
H2 Fächer im Aufbau
H3 Wir sind eine große, ehrenamtliche Community und gestalten Serlo
H3 Zusammen setzen wir uns für mehr Bildungsgerechtigkeit und die digitale Transformation unserer Schulen ein.
H3 Partner und Förderer
Some anchor texts are used more than once.
The number of internal links is ok.
None of the anchor texts is too long.
All internal links are not using dynamic parameters.
There are 6 external links on this page.

Found links on this page

LinkAttributesAnchor text
https://de.serlo.org/Anchor Inhalt
https://de.serlo.org/Anchor Footer
https://de.serlo.org/Die freie Lernplattform
IMG-ALT Serlo
https://de.serlo.org/auth/loginAnmelden
/mathe-pruefungen🎓 Ui, schon Prüfungszeit? Hier geht's zur Mathe-Prüfungsvorbereitung.
https://de.serlo.org/matheMathematik
/nachhaltigkeitNachhaltigkeit
https://de.serlo.org/biologieBiologie
https://de.serlo.org/chemieChemie
https://de.serlo.org/informatikInformatik
https://de.serlo.org/106081Fächer im Aufbau
https://de.serlo.org/serloMehr über uns
https://de.serlo.org/mitmachenMagst du mitmachen?
/user/profile/daniel-flueck@daniel-flueck Spender
IMG-ALT Avatar von daniel-flueck
/user/profile/metzgaria@metzgaria Lehrerin
IMG-ALT Avatar von metzgaria
/user/profile/wandapaetzold@wandapaetzold Autorin
IMG-ALT Avatar von wandapaetzold
/user/profile/nish@nish Team
IMG-ALT Avatar von nish
/user/profile/karin@karin Team
IMG-ALT Avatar von karin
/user/profile/flora_jana@flora_jana Team
IMG-ALT Avatar von flora_jana
/user/profile/Leogato@Leogato Team
IMG-ALT Avatar von Leogato
/user/profile/kathongi@kathongi Team
IMG-ALT Avatar von kathongi
/user/profile/wo_fo@wo_fo Autor
IMG-ALT Avatar von wo_fo
/user/profile/corinna@corinna Autorin
IMG-ALT Avatar von corinna
https://de.serlo.org/partnerAlle Partner ansehen
https://de.serlo.org/mitmachenMitmachen
https://de.serlo.org/serloÜber Serlo
https://de.serlo.org/kontaktKontakt
https://en.serlo.org/globalExternal Subdomain Other Languages
https://de.serlo.org/matheMathe
/mathe-pruefungenMathe Abschlussprüfungen
https://de.serlo.org/biologieText duplicate Biologie
/nachhaltigkeitAngewandte Nachhaltigkeit
https://de.serlo.org/informatikText duplicate Informatik
https://de.serlo.org/chemieText duplicate Chemie
https://de.serlo.org/lerntippsLerntipps
https://de.serlo.org/106081Text duplicate Fächer im Aufbau
https://serlo.us7.list-manage....External Subdomain Newsletter
https://de.serlo.org/jobsJobs
https://github.com/serloExternal GitHub
https://de.serlo.org/communityCommunity
https://en.serlo.org/editorExternal Subdomain Serlo Editor
https://en.serlo.org/metadataExternal Subdomain Metadata API
https://github.com/serlo/docum...External iFrame API
https://de.serlo.org/privacyDatenschutz
https://de.serlo.org/consentEinwilligungen widerrufen
https://de.serlo.org/termsNutzungsbedingungen und Urheberrecht
https://de.serlo.org/legalImpressum

Server configuration

HTTP redirects
(Critically important)
This page redirects to "https://de.serlo.org/"
HTTP header
(Important)
No X-Powered HTTP header is sent.
The web server transmits the web page (HTML) in compressed form.
Performance
(Somewhat important)
The page response time of 0.46 seconds is longer than the recommended limit of 0.4 seconds. A high response time unnecessarily slows down search engine crawling and results in bad user experience as well.
The file size of the HTML document is fine (157 kB).

HTTP Response Header

NameValue
dateThu, 24 Jul 2025 21:20:46 GMT
content-typetext/html; charset=utf-8
content-encodingzstd
cf-ray964676a39ee201bd-CDG
cf-cache-statusDYNAMIC
access-control-allow-origin*
age2634767
cache-controlpublic, max-age=0, must-revalidate
content-dispositioninline
strict-transport-securitymax-age=15552000; includeSubDomains
varyRSC, Next-Router-State-Tree, Next-Router-Prefetch, accept-encoding
x-content-type-optionsnosniff
x-matched-path/de
x-vercel-cacheHIT
x-vercel-idcdg1::zq9lw-1753392046955-df89950b72ae
report-to{"endpoints":[{"url":"https:\/\/a.nel.cloudflare.com\/report\/v4?s=g34X3RMQOwj4YP%2FXs8OV3XuA007HPdgJrCGNylx5XvNjLoKs3bj5AoBFqTsq3F9n%2FSn4l6PSyZ17ljyEzO2rT2mtatHwb%2FI%2FD%2BQ7UKDlX04WZ7Kd9hwELlnKvX%2FZXRg%3D"}],"group":"cf-nel","max_age":604800}
nel{"success_fraction":0,"report_to":"cf-nel","max_age":604800}
servercloudflare
alt-svch3=":443"; ma=86400
server-timingcfL4;desc="?proto=TCP&rtt=13590&min_rtt=13573&rtt_var=3850&sent=6&recv=8&lost=0&retrans=0&sent_bytes=3383&recv_bytes=903&delivery_rate=213364&cwnd=150&unsent_bytes=0&cid=e33de3d9b5b4d9e5&ts=340&x=0"
statuscode200
http_versionHTTP/2

External factors

This website has excellent links from other websites.
This page has backlinks from 284 referring domains.
This page has 3,946 backlinks.
This page has backlinks from 265 different ip addresses.

Links from Wikipedia

No links from Wikipedia were found.

Robots.txt

User-agent: *
Disallow: /page/revision/revisions/
Disallow: /page/revision/revision/
Disallow: /page/revision/
Disallow: /entity/repository/history/
Disallow: /entity/repository/compare/
Disallow: /backend
Disallow: /users
Disallow: /horizon
Disallow: /flag
Disallow: /license
Disallow: /uuid/recycle-bin
Disallow: /navigation/
Disallow: /authorization/
Disallow: /pages
Disallow: /uuid/recycle-bin
Disallow: /*/entity/trash-bin
Sitemap: https://de.serlo.org/sitemap.xml

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Search preview

Most important keywords

Following keywords were found. You can check the keyword optimization of this page for each keyword.

KeywordResultRecheck
Serlo65%Check
frei51%Check
möchtest50%Check
lernen50%Check
Lernplattform46%Check
freie46%Check
freie Lernplattform46%Check
frei lizenziert45%Check
Mathe43%Check
Partner42%Check
Show more keywords and terms

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