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d-centralize handbook

SEO

This section primarily focuses on the methods that we want to implement and adapt in every d-centralize project regarding improving SEO and Google Indexing.

The ultimate goal is to atract more users to our websites.

Technical SEO

Domain Internationalization

We want to use multiple domains to target users based on their region. For example, https://www.d-centralize.nl is dedicated to users in the Netherlands, ensuring a localized experience for Dutch inhabitants. Additionally, this domain can also serve Dutch-speaking users in other regions, such as Suriname.

For users outside of the Netherlands, we use https://www.d-centralize.com to provide a more globally recognized experience. We take into account our website internalization and try to provide the proper language to the users based on their region.

Hreflang Implementation

To optimize for international SEO, we implement hreflang tags as follows:

Primary Domain (Netherlands)

This is a HTML fragment seen on https://www.d-centralize.nl:

<link rel="alternate" href="https://www.d-centralize.nl" hreflang="nl-NL" />

The lowercase nl targets the user’s preferred language that is usually determined based on the value of the Accept-Language request header. Followingly, the uppercase NL marks the visitor’s region.

Special cases

For example, users coming from the Germany territory that might speak Dutch or German.

The goal is to cover both possibilities and use our both domains accordingly. For the German speakers we advise Google to index and provide as the result the .com domain:

<link rel="alternate" href="https://www.d-centralize.com/de" hreflang="de-DE" />

As for the Dutch speakers coming from Germany we advise Google to showcase the .nl domain:

<link rel="alternate" href="https://www.d-centralize.nl" hreflang="nl-DE" />

Other Locales

For each supported locale, we add the following to https://www.d-centralize.com served pages:

<link rel="alternate" href="https://www.d-centralize.com/{language}" hreflang="{language}-{region}" />

All users who are not specifically targeted by the NL region or the Dutch language (nl) as described in the special cases above - should be served the global domain at https://www.d-centralize.com/.

Default Hreflang Global Version

Based on our website’s supported languages we try to target multiple regions where the inhabitants from those regions speak the languages that we support. For example, we support the following languages: ['en', 'nl', 'de', 'fr', 'da'] and we are targeting the following regions based on the following country codes: ['GB', 'US', 'CA', 'AU', 'NL', 'DE', 'FR', 'DK'].

As an example, we try to target English (‘en’) speakers from Great Britain (‘GB’), United States (US), Canada (CA). Moreover, we are targeting Dutch (‘nl’) speakers from The Netherlands (‘NL’). And so on.

For users that are not targeted by our specific hreflang attributes that we define as exemplified above we set a x-default hreflang on all of our domains and as default we provide our English .com version to all users that are outside of our target:

<link rel="alternate" href="https://www.d-centralize.com" hreflang="x-default" />

This ensures users are directed to the correct version of the site based on their location and language preferences.

Sitemaps and robots.txt

To ensure optimal indexing, each domain should have its own sitemap.xml file, containing approximately 20–30 relevant pages.

NOTE: A relevant page is considered a page that is optimized for SEO in terms of technical SEO and also content SEO, meaning the canonical URLs are properly set, hreflang attributes, the page has also meta title, meta description, only one H1 element, H2s, H3s, etc. and also relevant content that uses specific keywords.

In a multi-domain setup, the goal is to generate a distinct sitemap per domain. For example:

Terminal window
https://www.d-centralize.nl/sitemap.xml
https://www.d-centralize.com/sitemap.xml

Each sitemap should only include pages intended to be indexed for that domain:

  • https://www.d-centralize.nl/sitemap.xml -> only includes Dutch pages with canonical URLs pointing to .nl
  • https://www.d-centralize.com/sitemap.xml -> includes all other pages (e.g. /de, /fr, etc.), with canonical URLs pointing to .com.

NOTE: Pages that have a canonical URL pointing to a different domain must not be included in the sitemap.

After generating the sitemaps, a corresponding robots.txt file is also generated for each domain. This file explicitly disallows indexing of any pages that shouldn’t be crawled or indexed by search engines.

URLs

Canonical URLs

WARNING: Canonical URLs must not point to a page with a redirect status code (e.g. 307 or 308), as search engines will ignore canonical tags on redirected pages.

Note: Geo-redirects based on user location do not work well with SEO and should be avoided where possible.

In a multi-domain setup where the same content is available under different domains, it’s crucial to manage canonical URLs properly to avoid SEO penalties for duplicate content.

Take the Pro6PP website as an example, which is available under both the .nl and .com domains. While the content is largely the same, the default language differs:

  • .nl domain: Default language is Dutch (/nl)
  • .com domain: Default language is English (/en)

The purpose of canonical URLs is to tell search engines which version of a page is the preferred one to index, helping to consolidate SEO signals and prevent duplicate content issues.

Example: English content on both domains

The Support page in English is accessible at the following URLs:

Terminal window
https://www.pro6pp.nl/en/support
https://www.pro6pp.com/support

Since we target English-speaking users globally via the .com domain, we set the canonical URL to:

<link rel="canonical" href="https://www.pro6pp.com/support" />
Example: Dutch content on both domains

The same Dutch-language page is accessible via both domains:

Terminal window
https://www.pro6pp.nl/webshops/magento-2-adresvalidatie-plugin
https://www.pro6pp.com/nl/webshops/magento-2-adresvalidatie-plugin

Because Dutch users are targeted via the .nl domain, the canonical URL is set to:

<link rel="canonical" href="https://www.pro6pp.nl/webshops/magento-2-adresvalidatie-plugin" />

Translated URLs

We implement translated URLs for each of the languages that we support on our websites.

For example, https://d-centralize.nl/about and https://d-centralize.nl/de/uber-uns.

This means that if a user visits us from Germany and we provide language support for German, then we provide translations to all the URLs in German. Also, based on the implementation of the hreflang attributes mentioned above, we also want Google to index the /de version of the website in the Google results for a user coming from Germany.

Content SEO

While technical SEO lays the foundation, proper content SEO ensures that each page is well-optimized for indexing and ranking in search engines.

A well-structured, content-optimized page should include:

  • A descriptive and keyword-rich meta title <title></title>
  • A concise and compelling meta description <meta content="" name="description">
  • One <h1> tag representing the main topic of the page
  • One or more <h2> tags for section titles
  • Optional <h3> and <h4> tags for deeper content structure
  • Paragraphs with relevant, informative, and keyword-aligned content

Keywords

Effective keyword research is essential and should be based on the locale and region of the targeted audience.

For example, if your site supports Dutch, you should perform keyword research focused on users in the Netherlands, using Dutch-language search terms.

The most important HTML elements to place your primary keywords include:

<title></title>
<meta content="" name="description">
<h1></h1>

Additionally, secondary and supporting keywords can be integrated naturally into headings (<h2>, <h3>, etc.) and paragraph content throughout the page.

A powerful tool to assist with keyword discovery and analysis is SERanking. The company account can be found in Bitwarden and its license currently allows 3 sites.

SERanking

SERanking also offers a comprehensive Website Audit feature that crawls all website pages and provides a detailed SEO report, including a score from 1 to 100.

The audit covers key SEO areas such as:

  • Crawling & Indexing
  • Redirects
  • Sitemap
  • Meta Tags
  • Content
  • Localization
  • Links
  • Other

The target is to achieve a score of 90 or above to ensure that the website is considered well-optimized from an SEO perspective.