diff --git a/2-Application/src/main/java/tag/CustomTagsUseCase.java b/2-Application/src/main/java/tag/CustomTagsUseCase.java
new file mode 100644
index 0000000..8438b9b
--- /dev/null
+++ b/2-Application/src/main/java/tag/CustomTagsUseCase.java
@@ -0,0 +1,16 @@
+package tag;
+
+import tag.matcherImplementations.CustomTagMatcher;
+
+public class CustomTagsUseCase {
+
+	private final TagMatcherRepository tagMatcherRepository;
+
+	public CustomTagsUseCase(TagMatcherRepository tagMatcherRepository) {
+		this.tagMatcherRepository = tagMatcherRepository;
+	}
+
+	public void addCustomTagMatcher(CustomTagMatcher customTagMatcher) {
+		tagMatcherRepository.addCustomTagMatcher(customTagMatcher);
+	}
+}
diff --git a/3-Domain/src/main/java/abstraction/PersistenceAdapter.java b/3-Domain/src/main/java/abstraction/PersistenceAdapter.java
index 98ee6b8..199b4aa 100644
--- a/3-Domain/src/main/java/abstraction/PersistenceAdapter.java
+++ b/3-Domain/src/main/java/abstraction/PersistenceAdapter.java
@@ -5,7 +5,7 @@ import java.util.Set;
 public interface PersistenceAdapter<T> {
 
 	Set<T> getAll();
-	Boolean add(T value);
-	Boolean remove(T value);
+	void add(T value);
+	void remove(T value);
 
 }
diff --git a/3-Domain/src/main/java/exeptions/TagMatcherAlreadyExists.java b/3-Domain/src/main/java/exeptions/TagMatcherAlreadyExists.java
new file mode 100644
index 0000000..5f9368c
--- /dev/null
+++ b/3-Domain/src/main/java/exeptions/TagMatcherAlreadyExists.java
@@ -0,0 +1,10 @@
+package exeptions;
+
+import tag.TagName;
+
+public class TagMatcherAlreadyExists extends RuntimeException {
+
+	public TagMatcherAlreadyExists(TagName name) {
+		super("A Tag Matcher with the name " + name + " already exists.");
+	}
+}
diff --git a/3-Domain/src/main/java/tag/TagMatcher.java b/3-Domain/src/main/java/tag/TagMatcher.java
index 86177b7..8122d6b 100644
--- a/3-Domain/src/main/java/tag/TagMatcher.java
+++ b/3-Domain/src/main/java/tag/TagMatcher.java
@@ -2,11 +2,28 @@ package tag;
 
 import link.LinkUrl;
 
-import java.util.Collection;
-import java.util.Optional;
+import java.util.Objects;
 
-public interface TagMatcher {
+public abstract class TagMatcher {
 
-	OptionalTag ifMatches(LinkUrl linkUrl);
+	protected TagName tagName;
 
+	public TagName getTagName() {
+		return tagName;
+	}
+
+	protected abstract OptionalTag ifMatches(LinkUrl linkUrl);
+
+	@Override
+	public boolean equals(Object o) {
+		if (this == o) return true;
+		if (!(o instanceof TagMatcher that)) return false;
+
+		return Objects.equals(tagName, that.tagName);
+	}
+
+	@Override
+	public int hashCode() {
+		return tagName != null ? tagName.hashCode() : 0;
+	}
 }
diff --git a/3-Domain/src/main/java/tag/TagMatcherRepository.java b/3-Domain/src/main/java/tag/TagMatcherRepository.java
index c609884..6577cf7 100644
--- a/3-Domain/src/main/java/tag/TagMatcherRepository.java
+++ b/3-Domain/src/main/java/tag/TagMatcherRepository.java
@@ -1,18 +1,49 @@
 package tag;
 
+import abstraction.CustomSet;
+import abstraction.CustomSetPersistenceDecorator;
+import abstraction.PersistenceAdapter;
+import exeptions.TagMatcherAlreadyExists;
+import tag.matcherImplementations.CustomTagMatcher;
+
 import java.util.HashSet;
 import java.util.Set;
+import java.util.function.Predicate;
 
 public class TagMatcherRepository {
 
-	Set<TagMatcher> tagMatchers = Set.of();
+	final Set<TagMatcher> staticTagMatchers;
 
-	public TagMatcherRepository(final TagPersistenceAdapter tagPersistenceAdapter, final Set<TagMatcher> staticTagMatchers) {
-		tagMatchers.addAll(staticTagMatchers);
-		tagMatchers.addAll(tagPersistenceAdapter.getCustomTagMatchers());
+	final private CustomSet<CustomTagMatcher> customTagMatchers;
+
+	public TagMatcherRepository(final PersistenceAdapter<CustomTagMatcher> customTagMatcherPersistenceAdapter,
+	                            final Set<TagMatcher> staticTagMatchers) {
+		this.staticTagMatchers = staticTagMatchers;
+		this.customTagMatchers =
+				new CustomSetPersistenceDecorator<CustomTagMatcher>(customTagMatcherPersistenceAdapter);
 	}
 
 	public Set<TagMatcher> getTagMatchers() {
-		return new HashSet<>(tagMatchers);
+		var set = new HashSet<TagMatcher>(staticTagMatchers);
+		set.addAll(customTagMatchers.getSet());
+		return set;
+	}
+
+	public void addCustomTagMatcher(CustomTagMatcher customTagMatcher) {
+		checkDuplicates(customTagMatcher);
+
+		customTagMatchers.add(customTagMatcher);
+	}
+
+	private void checkDuplicates(CustomTagMatcher customTagMatcher) {
+		Predicate<TagMatcher> predicate = matcher -> (matcher.tagName.equals(customTagMatcher.getTagName()));
+		var alreadyExists = staticTagMatchers.stream().anyMatch(predicate) || customTagMatchers
+				.getSet()
+				.stream()
+				.anyMatch(predicate);
+
+		if (alreadyExists) {
+			throw new TagMatcherAlreadyExists(customTagMatcher.tagName);
+		}
 	}
 }
diff --git a/3-Domain/src/main/java/tag/matcherImplementations/CustomTagMatcher.java b/3-Domain/src/main/java/tag/matcherImplementations/CustomTagMatcher.java
index 083aaa6..ed64255 100644
--- a/3-Domain/src/main/java/tag/matcherImplementations/CustomTagMatcher.java
+++ b/3-Domain/src/main/java/tag/matcherImplementations/CustomTagMatcher.java
@@ -9,10 +9,9 @@ import tag.TagName;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
-public class CustomTagMatcher implements TagMatcher {
+public class CustomTagMatcher extends TagMatcher {
 
 	private final Pattern regex;
-	private final TagName tagName;
 
 	public CustomTagMatcher(TagName name, String regexString) {
 		this.regex = Pattern.compile(regexString); // TODO this could throw??
@@ -28,5 +27,4 @@ public class CustomTagMatcher implements TagMatcher {
 		}
 		return OptionalTag.empty();
 	}
-
 }
diff --git a/3-Domain/src/main/java/tag/matcherImplementations/GitHubTagMatcher.java b/3-Domain/src/main/java/tag/matcherImplementations/GitHubTagMatcher.java
index 5acf3e1..f9e299a 100644
--- a/3-Domain/src/main/java/tag/matcherImplementations/GitHubTagMatcher.java
+++ b/3-Domain/src/main/java/tag/matcherImplementations/GitHubTagMatcher.java
@@ -6,10 +6,12 @@ import tag.Tag;
 import tag.TagMatcher;
 import tag.TagName;
 
-public class GitHubTagMatcher implements TagMatcher {
+public class GitHubTagMatcher extends TagMatcher {
+
+	private final TagName tagName = new TagName("github");
 
 	public TagName getName() {
-		return new TagName("github");
+		return tagName;
 	}
 
 	public String getAdditionInfo() {