diff --git a/komga/src/flyway/resources/db/migration/sqlite/V20200906115600__lower_trim_tags.sql b/komga/src/flyway/resources/db/migration/sqlite/V20200906115600__lower_trim_tags.sql
new file mode 100644
index 000000000..a49a7b0b9
--- /dev/null
+++ b/komga/src/flyway/resources/db/migration/sqlite/V20200906115600__lower_trim_tags.sql
@@ -0,0 +1,37 @@
+UPDATE BOOK_METADATA_TAG
+SET tag = lower(trim(tag));
+
+delete
+from BOOK_METADATA_TAG
+where ROWID not in
+      (
+          select min(rowid)
+          from BOOK_METADATA_TAG
+          group by tag, BOOK_ID
+      );
+
+
+UPDATE SERIES_METADATA_TAG
+SET tag = lower(trim(tag));
+
+delete
+from SERIES_METADATA_TAG
+where ROWID not in
+      (
+          select min(rowid)
+          from SERIES_METADATA_TAG
+          group by tag, SERIES_ID
+      );
+
+
+UPDATE SERIES_METADATA_GENRE
+SET GENRE = lower(trim(GENRE));
+
+delete
+from SERIES_METADATA_GENRE
+where ROWID not in
+      (
+          select min(rowid)
+          from SERIES_METADATA_GENRE
+          group by GENRE, SERIES_ID
+      );
diff --git a/komga/src/main/kotlin/org/gotson/komga/domain/model/BookMetadata.kt b/komga/src/main/kotlin/org/gotson/komga/domain/model/BookMetadata.kt
index ef0e24f52..20b4fee47 100644
--- a/komga/src/main/kotlin/org/gotson/komga/domain/model/BookMetadata.kt
+++ b/komga/src/main/kotlin/org/gotson/komga/domain/model/BookMetadata.kt
@@ -10,7 +10,7 @@ class BookMetadata(
   val numberSort: Float,
   val releaseDate: LocalDate? = null,
   val authors: List<Author> = emptyList(),
-  val tags: Set<String> = emptySet(),
+  tags: Set<String> = emptySet(),
 
   val titleLock: Boolean = false,
   val summaryLock: Boolean = false,
@@ -29,6 +29,7 @@ class BookMetadata(
   val title = title.trim()
   val summary = summary.trim()
   val number = number.trim()
+  val tags = tags.map { it.toLowerCase().trim() }.filter { it.isNotBlank() }.toSet()
 
   fun copy(
     title: String = this.title,
diff --git a/komga/src/main/kotlin/org/gotson/komga/domain/model/SeriesMetadata.kt b/komga/src/main/kotlin/org/gotson/komga/domain/model/SeriesMetadata.kt
index e093e3462..6cad4dfec 100644
--- a/komga/src/main/kotlin/org/gotson/komga/domain/model/SeriesMetadata.kt
+++ b/komga/src/main/kotlin/org/gotson/komga/domain/model/SeriesMetadata.kt
@@ -11,8 +11,8 @@ class SeriesMetadata(
   publisher: String = "",
   val ageRating: Int? = null,
   val language: String = "",
-  val genres: Set<String> = emptySet(),
-  val tags: Set<String> = emptySet(),
+  genres: Set<String> = emptySet(),
+  tags: Set<String> = emptySet(),
 
   val statusLock: Boolean = false,
   val titleLock: Boolean = false,
@@ -34,6 +34,8 @@ class SeriesMetadata(
   val titleSort = titleSort.trim()
   val summary = summary.trim()
   val publisher = publisher.trim()
+  val tags = tags.map { it.toLowerCase().trim() }.filter { it.isNotBlank() }.toSet()
+  val genres = genres.map { it.toLowerCase().trim() }.filter { it.isNotBlank() }.toSet()
 
   fun copy(
     status: Status = this.status,