SEO Encyclopedia in 2025

Above the fold

Refers to the visible area in a browser without scrolling.
Originally, the meaning comes from the print area and describes the print fold in printing.
The opposite is "Under the fold"


AI tools for SEO

In 2025, there are numerous AI tools that support SEOs – from content optimization to data analysis. Use these tools to recognize patterns (e.g., keyword groupings via cluster analysis) or automatically create meta descriptions. But don't blindly rely on AI: always check the results manually. Used correctly, AI tools can accelerate routine tasks and uncover new optimization potentials.


AI-generated content

Use AI tools (e.g., ChatGPT) for content creation with caution. You should always check and adapt AI texts for accuracy, uniqueness, and added value. Google treats AI content no differently than human-written content – what matters is that it is helpful and high-quality.


AI-powered search

Search engines in 2025 increasingly integrate AI (e.g., Google's Search Generative Experience). Make sure to provide content that answers user questions precisely and in a structured way. This increases the chance that AI-based search functions will display your site as a helpful source.


Backlinks

Backlinks – i.e., links from other websites to yours – remain an important ranking factor. Quality counts more than quantity here: a few links from trustworthy, topically relevant sites bring more than many weak links. Focus on obtaining natural references through good content and outreach rather than buying links or generating them through spam.


Bing AI search

Bing has integrated ChatGPT into search and delivers AI-powered answers. Therefore, you should not neglect Bing. Make sure your website offers high-quality, well-structured content so it becomes visible in Bing AI search as well.


Black Hat SEO

Black Hat SEO refers to prohibited methods like cloaking, hidden texts, or massive link buying to manipulate rankings. Such techniques may bring short-term success but often lead to penalties by Google. Stick to Google guidelines and rely on sustainable optimization – short-term tricks are not worth it and endanger your visibility long-term.


Branding and SEO

A strong brand also pays off in SEO. When users specifically search for your brand, Google gets the signal that your website is trustworthy and well-known. Therefore, build your brand awareness – for example through social media activities, PR, and recommendations. Additionally, users in search results are more likely to click on familiar names, which increases your click-through rate and can thus indirectly positively influence your ranking.


Broken links

Regularly check your website for broken links (404 errors). Broken internal links make crawlers' work difficult and frustrate users. Repair or remove broken links promptly, and set 301 redirects if necessary when pages have been moved. Error-free linking signals quality and care.


Content freshness

Freshness can be a ranking factor for certain topics. Regularly review older content and keep it up to date. Updated publication dates, fresh examples, or new insights show Google that your site is maintained and remains relevant for users.


Content pruning

Remove or revise outdated and weak content (content pruning). Pages that bring no traffic or are not convincing in quality can affect the overall performance of your website. By cleaning out old content, you improve the average quality and focus of your site, which can positively affect ranking.


Content quality

The quality of your content is crucial. Write comprehensive, well-structured texts that provide value to the reader. Avoid phrases and filler words – every sentence should be useful. The higher the content quality, the better user satisfaction and ranking will be.


Content structure

Structure your content with headings (H1-H6), paragraphs, and lists. A clear structure helps both your readers and search engines to quickly grasp the content. Use meaningful headings that summarize the topic – so crawlers and users immediately understand what the following section is about.


Core Web Vitals

The Core Web Vitals are three performance metrics for user experience: Largest Contentful Paint (loading time to main content), First Input Delay (response time to first user action), and Cumulative Layout Shift (visual stability). Optimize your website to be in the green range for these metrics (e.g., LCP < 2.5s). Improving Core Web Vitals can positively affect your ranking as Google uses them as part of the Page Experience signal.


core web vitals

With the Core Web Vitals, Google introduces a new KPI to measure and evaluate user experience. Using three parameters, website owners can check whether all SEO-relevant aspects are met and whether visitors to the site can use all functions without problems. These three parameters focus on loading time duration, stability, and interaction between visitor and website. The Core Web Vitals are another component of Page Experience, which has been part of Google's algorithm since June 2021.

The three metrics

Already at the beginning of May 2020, Google announced the Core Web Vitals as a new tool for SEO. The three metrics of this new system are, alongside many other values, part of a new ranking system that should measure stability and user experience so that these values can continue to be optimized.

The Web Vitals currently consist of the following three values:

Largest Contentful Paint (page loading time)

First Input Delay (user interaction with the page)

Cumulative Layout Shift (website stability)


The great advantage of these values is that they come from real user data and are therefore perfectly suited for representative purposes. In an annual evaluation, the Web Vitals should be continuously adapted and improved. It is therefore quite possible that there could still be smaller to larger changes in these three core metrics.

The advantages of these values

By focusing on these three fundamental values, several advantages arise. On one hand, it is possible for Google to evaluate websites based on very clear KPIs, and on the other hand, the values provide website owners with a solid argumentative basis for their visitors and customers. Also with regard to optimizations of one's own website, possible sources of error or problem areas can be identified and classified relatively quickly
and cleaned up accordingly.
Core Web Vitals in detail

The loading speed of the website - Largest Contentful Paint

With the LCP metric, the loading time of a website is measured. An extremely important factor for user experience. Because the more content there is on the page, the longer it loads, which in turn can deter potential customers of the site or at least be noticed negatively.

Google specifies here that values up to 2.5 seconds represent optimal, values between 2.5 to 4 seconds represent mediocre, and values from 4 seconds represent poor loading time.

Optimizing long loading times

If the loading times of the website are too long, then this has various reasons. On one hand, there seems to be no efficient cache, i.e., a buffer, and on the other hand, Google recommends a framework instead of using a complete HTML page. Also, content blocks that are too large or high-resolution videos and images can negatively affect the loading time of the website.


User interaction with the website - First Input Delay

The second metric FID describes the interaction of the visitor with the website. In detail, this means that the time span is measured between the first interaction of the user on the site and the reaction of the browser. Because often visitors to websites immediately click on a button or want to interact with a text box before the page has even fully loaded all elements. Of course, the page will not show any reaction in this case. So that the visitor to the site does not immediately leave again because he mistakenly thinks that the site is not working, exactly this delay is measured and optimized if necessary.

Here too, Google again suggests corresponding values. The company describes a good value as up to 100 milliseconds. Values between 100 and 300 milliseconds are considered expandable, while everything from 300 milliseconds counts as extremely negative.

Optimizing FID

In case of a poor value of 300 milliseconds or more, there are also some suggestions here for what can be done. For example, Long Tasks can be split up. This describes the phases in which the JavaScript of the page executes certain functions and therefore cannot respond accordingly. On the other hand, certain interactions can also be prioritized. For example, code fragments that are crucial for the interaction between user and website can be loaded first.

Is the website stable enough? - Cumulative Layout Shift

The third and last value so far, CLS, is a metric that describes the visual stability of the website when an interaction occurs on it. It can often happen that smaller shifts in the layout occur when certain elements are loaded first. This can cause, for example, a text block or an image element to slide down and overlay another element. This naturally doesn't look good to the visitor of the website at first and seems rather unprofessional.

It becomes particularly difficult with online shops or pages that have implemented important functions. Because if the visual stability of a website is not given and certain elements slip during interaction, it can happen that the user of the page, for example, makes a wrong input and thus triggers unwanted functions.

The CLS is calculated as follows: "Impact Fraction x Distance Fraction = Layout Shift Score"

Impact Fraction = Area of the screen in percent

Distance Fraction = Percentage of viewport height

The result that emerges from this calculation should now be a value between 0 and 1. Here Google gives a value up to 0.1 as positive and everything from 0.25 as negative.

Optimizing CLS

If a website struggles with visual instability, then it usually helps to provide all images and videos on the page with width and height specifications. Web fonts can also often bring problems with regard to stability. The recommendation here is clearly to preload all fonts.


The Core Web Vitals - a perfect measuring instrument for SEO

Anyone who has not yet dealt with the three metrics of the Core Web Vitals should definitely do so soon. Problems with regard to user experience can thus be directly classified and optimized in a timely manner. Google provides here a large selection of optimization tools as well as extremely meticulous documentation, so that all functions are clear and understandable for every webmaster. Anyone who wants to provide the users of his website with a pleasant visiting experience should now check and optimize his site with the three new metrics.


Crawl budget

Especially for large websites, crawl budget is important – i.e., the number of pages Google visits per time. Help the crawler by blocking unimportant pages (e.g., filters, session IDs) via robots.txt and providing a current XML sitemap. The more efficiently Google can crawl on your site, the better new or changed content will be indexed.


Duplicate content

Avoid duplicate content on your website as it can lead to ranking problems. If similar content is necessary (e.g., for print versions or multilingual pages), use canonical tags to mark the main version. Search engines prefer unique, original content per page.


E-E-A-T

E-E-A-T (Experience, Expertise, Authoritativeness, Trustworthiness) is central in 2025. Show your experience and expertise, e.g., through transparent authorship and references. Build trust by providing a complete imprint, privacy information, and high-quality, error-free content.


Entities

Google analyzes texts for entities (people, places, things). Use clear names and terms so the search engine can properly classify your content. When Google recognizes and links the entities on your page (Knowledge Graph), it increases your thematic relevance.


Evergreen content

Focus on evergreen content: content that remains relevant long-term. Such timeless guides or tutorials bring continuous traffic without you having to constantly revise them. Make sure that evergreen topics are still occasionally checked and slightly updated so they appear current and remain competitive.


Featured snippets

Featured snippets are highlighted results above the organic hits that provide a direct answer (often in the form of text excerpts, lists, or tables). To achieve a featured snippet, answer common questions about your topic concisely in your content. Use clear question-answer formats or lists. If Google rates your answer as particularly helpful, it may place it as a featured snippet.


Google Core Updates

Google adjusts its algorithm several times a year with Core Updates. These core updates often focus on content quality and relevance. If you are affected by an update, check your site for possible weaknesses in content, user experience, or E-E-A-T and optimize accordingly. A sustainable content strategy protects you best from negative update effects.


Google Discover

Google Discover shows users personalized content even without active search. To appear here, create content with high utility value and appealing images above all. Freshness and E-E-A-T also play a role. Use interesting headlines (no clickbait) and meta descriptions so your post makes people curious in Discover. Note: Google Discover brings unpredictable traffic, but high-quality, visually appealing content increases the chance of inclusion.


Google MUM

Google MUM (Multitask Unified Model) understands complex queries across texts, images, and languages. Therefore, provide diverse content (text, images, videos) and cover a topic comprehensively. The more holistically you treat a topic, the better MUM can assign your site to matching search queries.


Google Search Console

Use Google Search Console to monitor your website's performance. Here you learn which keywords bring traffic, whether indexing problems exist, and how your Core Web Vitals are rated. Through Search Console, you can also submit sitemaps and manually request Google to crawl – an indispensable tool for SEO.


h1

The H1 tag basically shows the search engine what topic the page is about.
It is a myth to believe that the website may have only exactly one H1 tag.
Google itself has explained that multiple H1 tags are fine:


https://www.youtube.com/watch?v=UILcrHaO7m4&feature=youtu.be&t=8m59s


Hreflang

Hreflang tags help Google deliver the right language or country version of your site. If you have multilingual content, add hreflang link tags in the HTML of a page that point to the corresponding translation. Make sure hreflang pairs are reciprocal and use correct language and country codes (e.g., en-US for English in the United States). This way you avoid duplicate content across country borders and serve users with the appropriate version.


Image SEO

Images can bring considerable traffic via Google image search. Therefore, optimize every image: use a descriptive file name and fill the alt attribute with a meaningful, concise text that describes the image content. Compress images to an appropriate file size so loading time remains low. With structured data (ImageObject) and an image sitemap, you can provide Google with additional info about your images.


IndexNow

IndexNow is a protocol with which you can immediately inform search engines (Bing, Yandex – Google is still testing) about new or updated content. If you support it, your website proactively sends URLs to participating search engines. This way, new content outside of Google – especially at Bing – is indexed significantly faster.


Internal linking

Link your pages internally in a meaningful way to signal to Google the importance of individual subpages. Use descriptive anchor texts for internal links that reflect the target topic. Strong internal linking helps distribute link juice within your website and improves the findability of new or deep content.


JavaScript SEO

If your website is heavily based on JavaScript, pay attention to SEO aspects. Google can render JS, but there may be delays in indexing. Make sure important content is not only loaded later via JS or provide a fallback (e.g., SSR or dynamic rendering). Check with tools like the URL Inspection tool in Search Console whether Google sees your JS content.


keyword

The keyword that Google should respond to.


Keyword cannibalization

Multiple pages of your website should not compete for the same keyword. Check if you are practicing cannibalization – i.e., if different subpages target the same search query. It is better to merge such content or clearly differentiate it so Google clearly recognizes which page should rank for which keyword.


Link building

In link building (offpage SEO), you should proceed sustainably. Create content that others like to link to (linkbait), or do targeted outreach to build backlinks. Avoid unnatural link patterns and purchased links – Google increasingly recognizes manipulative linkbuilding methods and punishes them. Instead, rely on PR, guest posts, or cooperations to get real recommendations.


Local SEO

For local businesses, "Local SEO" is crucial. Maintain your Google Business Profile (formerly Google My Business) with current data, reviews, and photos. Optimize your website for local keywords (including place names) and present name, address, phone number (NAP) consistently. Local directory entries and reviews can improve your local ranking so you become visible in Google map search (Local Pack).


Long-tail keywords

Long-tail keywords are longer, more specific search queries with lower search volume but often high purchase or action intent. By covering such specific keywords, you can more easily achieve top rankings and attract very targeted visitors. Create content that specifically addresses these niche queries.


Manual action

If your website violates Google's guidelines, a manual action (penalty) can be imposed. Then your ranking is drastically worsened or pages are completely removed from the index. To avoid this, refrain from unfair methods and monitor Search Console for warnings. If you receive a manual action, fix the problems (e.g., remove spam links or thin content) and submit a reconsideration request to have the penalty lifted.


meta tags

Meta tags are specifications in the source code of the HTML document. They contain, among other things, information for search engines.

Attention: Google does not read the meta tag "keywords". So you can save time and completely omit this tag!


Mobile-first indexing

Google primarily indexes the mobile version of your website. Make sure your site is as complete and optimized on mobile as on desktop. Responsive design, fast loading times, and good mobile usability are mandatory so you don't have disadvantages in the mobile-first index.


Myths

There are many myths surrounding SEO and Google.

For example, Google does not crawl the meta tag keyword and multiple H1 tags on a page are quite ok.

See Google video on H1 tag:

https://www.youtube.com/watch?v=UILcrHaO7m4&feature=youtu.be&t=8m59s

 


Noindex tag

With the noindex meta tag, you can instruct search engines not to include a page in the index. Use strategically, e.g., for pages with thin content, duplicates, or internal areas that should not appear in search results. Note: noindex pages are not listed by Google, but crawlers can still follow them if links point to them.


onpage

Onpage describes all measures taken to optimize the website with regard to ranking and/or a keyword.


Page Experience

Page Experience includes factors like loading speed, mobile usability, security, and page stability. Google evaluates user experience: consistently good page experience across the site can improve your ranking. Therefore, pay attention to fast servers, mobile optimization, HTTPS, and avoid intrusive interstitials.


Pagespeed

The Google Pagespeed is an indicator of how fast your website loads.
Google uses the value to consider how valuable your site is in terms of speed.

You can check your site's PageSpeed here:

https://developers.google.com/speed/pagespeed/insights/?hl=en

It's not just about the size of your website and the speed of your internet connection.

Much more important is: Which files block rendering in the browser. How fast does the website need until it displays content. etc.

 


Pagination

For paginated pages (e.g., category pages 1, 2, 3), there is no special markup for Google since the removal of rel="next/prev". Make sure users and crawlers can easily reach the relevant page. Good internal linking (e.g., "Show all products") and clear page numbering help Google fully capture your content despite pagination.


Personalized search

Google personalizes search results according to the user's location, search history, and interests. While you have little direct influence on this, ensure overall strong signals (local relevance, brand mentions, social media presence). This way the chances are good that your site is also visible in personalized results.


Rich snippets

Rich snippets are enhanced search result displays with additional information (star ratings, images, price information, etc.). They often arise from structured data on your site. With correctly implemented schema markup, you increase the likelihood that Google displays such rich snippets for your pages – which can lead to a higher click-through rate.


robots.txt

robots.txt is a file that can be used to control Google.
Here you specify which files, images, or folders should be excluded from the search index.
Entire search engines can be excluded.

The sitemap.xml file is also entered in the robots.txt file.


Search intent

Make sure your content meets the user's search intent. For every keyword, consider what the searcher really wants to know or do. If you provide the right answer or solution, the visitor stays longer on your page and Google rates your site as more relevant.


Semantic search

Google today better understands the context and meaning of words. Make sure to treat a topic holistically instead of just repeating a keyword. Use synonyms and topic-related terms so search engines can capture the semantic connection and recognize your content as comprehensive.


SEO Text

I assume that Google will increasingly use Natural Language Processing (NLP) to interpret texts and capture their content. This leads to the following recommendations for good SEO text:

1.) When creating texts, write grammatically clean, clear, and above all simple. Don't use nested sentences. They belong in a good dissertation, but not on a webpage. Also avoid many subordinate clauses. What is good for readers cannot be bad for search engines.

2.) Avoid personal pronouns. Name the entity (unit, brand) by name so Google can clearly understand what is meant.

3.) Only use adverbs and adjectives if they are really important for understanding a sentence.

In summary, completely avoid waffle and blah blah to do Google and thus also readers a favor.

Summary: Become a brand and an authority!!


SERP

SERP is the English abbreviation for Search Engine Result Pages. SERPs are nothing other than the organic search results that are shown when you have entered a search term on Google. So they are not the ads delivered by Google Ads.


Sitemap.xml

A sitemap.xml is a file that informs Google which pages your website has.
So that Google can find the sitemap, it should be entered in the robots.txt file.

Example robots.txt:
Sitemap: https://www.yourdomainname.com/sitemap.xml

Google will read the sitemap at regular intervals. So it makes sense to keep the sitemap current.


Snippet optimization

Optimize your snippets (page title and meta description) for a higher click-through rate. Write concise, meaningful titles with the main keyword preferably at the front. The meta description should make people curious and briefly summarize the topic – it may directly address the user. An attractive snippet sets you apart from other hits and can bring more clicks to your site despite the same ranking.


Structured data

Structured data (Schema.org markup) provides additional information for search engines in the source code. Through markup (e.g., JSON-LD), you can tell Google details – such as reviews, recipes, FAQs – which then appear as rich results in the SERP. Implement relevant schema types for your content (article, product, FAQ, etc.) to increase your chances of conspicuous displays in search results.


Topic authority

Show Google that you comprehensively cover a topic. Create thematically related posts and link them internally to form a content hub. When your website offers many high-quality contents on one area, you are perceived as an authority – this can improve your ranking for all related keywords.


Under the fold

Refers to the not immediately visible area.
In SEO, this is the area where speed can be optimized when mobile pages only load images when they come into the visible area. This ensures that the "Above the fold" area (i.e., the immediately visible area) loads faster. Google will give you plus points for this and your page will rank better.


User signals

Even though Google officially doesn't confirm user signals like click-through rate or dwell time as direct ranking factors, they can play an indirect role. A low bounce rate and longer visit duration signal that your content is relevant and engaging. Therefore, optimize the usability and content of your site so visitors like to stay and interact. Satisfied users lead to better rankings in the long term.


Video SEO

Videos are prominently displayed in search results and on YouTube. Use video SEO: create an optimized title, a meaningful description, and tags for your videos. Embed your videos meaningfully on your site and use video schema.org markup. Transcripts or subtitles help search engines understand video content. Through video SEO, you can gain visibility both on YouTube and in Google search results.


Visual search

More and more users use visual search (e.g., Google Lens) to find information about images. Make sure your images are SEO-optimized: use descriptive file names, alt texts, and surrounding text that explains the image content. This way search engines can capture the context. With visual search, users can find your site if your image matches the searched object.


Voice search

In voice search, users often ask longer, naturally formulated questions. Therefore, optimize your content also for complete questions and colloquial formulations. A good strategy is to create FAQ sections that briefly answer typical W-questions. This increases the chance that voice assistants (e.g., Siri, Google Assistant) will read your site as an answer.


wdf*idf

Keyword density was yesterday. Anyone who wants to rank well on Google today needs somewhat better content than writing the word: MyKeyword 10 times in a row in the content.

The solution, thanks to the legendary blog article by Karl Kratz, is: wdf*idf.
Until there is something better, the wdf*idf formula is considered the jack-of-all-trades.

So the ratio of the occurrence of a term in relation to its weighting in the text. Basically a mathematical formula.

Of course, wdf*idf optimized content is no guarantee for a TOP ranking on Google. As with everything in SEO, the overall mix is what matters here too.


Website structure

A clear website structure helps search engines with indexing. Organize your content hierarchically (homepage ? categories ? subpages) and create clear navigation. A good structure ensures that crawlers find all important pages and users can easily navigate.


Zero-click search

For more and more search queries, users get the answer directly on the Google results page (zero-click). This includes featured snippets, knowledge panels, weather, currency converters, etc. For websites, this means: still provide valuable information, but don't always expect a click. Optimize your content so it provides value both on your site and directly in search results (e.g., through concise summaries or structured data).