diff --git a/3-Domain/src/main/java/tag/Tag.java b/3-Domain/src/main/java/tag/Tag.java
new file mode 100644
index 0000000..b40463c
--- /dev/null
+++ b/3-Domain/src/main/java/tag/Tag.java
@@ -0,0 +1,5 @@
+package tag;
+
+public record Tag(TagName name, String additionalData) {
+
+}
diff --git a/3-Domain/src/main/java/tag/TagMatcher.java b/3-Domain/src/main/java/tag/TagMatcher.java
new file mode 100644
index 0000000..58bc29b
--- /dev/null
+++ b/3-Domain/src/main/java/tag/TagMatcher.java
@@ -0,0 +1,10 @@
+package tag;
+
+import link.LinkUrl;
+
+import java.util.Optional;
+
+public interface TagMatcher {
+
+	Optional<Tag> matches(LinkUrl linkUrl);
+}
diff --git a/3-Domain/src/main/java/tag/TagName.java b/3-Domain/src/main/java/tag/TagName.java
new file mode 100644
index 0000000..edcc0ab
--- /dev/null
+++ b/3-Domain/src/main/java/tag/TagName.java
@@ -0,0 +1,5 @@
+package tag;
+
+public record TagName(String name) {
+
+}
diff --git a/3-Domain/src/main/java/tag/matcherImplementations/CustomTagMatcher.java b/3-Domain/src/main/java/tag/matcherImplementations/CustomTagMatcher.java
new file mode 100644
index 0000000..322dccb
--- /dev/null
+++ b/3-Domain/src/main/java/tag/matcherImplementations/CustomTagMatcher.java
@@ -0,0 +1,32 @@
+package tag.matcherImplementations;
+
+import link.LinkUrl;
+import tag.Tag;
+import tag.TagMatcher;
+import tag.TagName;
+
+import java.util.Optional;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+public class CustomTagMatcher implements TagMatcher {
+
+	private final Pattern regex;
+	private final TagName tagName;
+
+	public CustomTagMatcher(TagName name, String regexString) {
+		this.regex = Pattern.compile(regexString); // TODO this could throw??
+		this.tagName = name;
+	}
+
+	@Override
+	public Optional<Tag> matches(LinkUrl linkUrl) {
+		Matcher matcher = regex.matcher(linkUrl.toString());
+
+		if (matcher.find()) {
+			return Optional.of(new Tag(this.tagName, ""));
+		}
+		return Optional.empty();
+	}
+
+}
diff --git a/3-Domain/src/main/java/tag/matcherImplementations/GitHubTagMatcher.java b/3-Domain/src/main/java/tag/matcherImplementations/GitHubTagMatcher.java
new file mode 100644
index 0000000..b87ebec
--- /dev/null
+++ b/3-Domain/src/main/java/tag/matcherImplementations/GitHubTagMatcher.java
@@ -0,0 +1,27 @@
+package tag.matcherImplementations;
+
+import link.LinkUrl;
+import tag.Tag;
+import tag.TagMatcher;
+import tag.TagName;
+
+import java.util.Optional;
+
+public class GitHubTagMatcher implements TagMatcher {
+
+	public TagName getName() {
+		return new TagName("github");
+	}
+
+	public String getAdditionInfo() {
+		return null;
+	}
+
+	@Override
+	public Optional<Tag> matches(LinkUrl linkUrl) {
+		if (linkUrl.getUrl().getHost().equals("github.com")) {
+			return Optional.of(new Tag(getName(), getAdditionInfo()));
+		}
+		return Optional.empty();
+	}
+}