diff --git a/Cargo.lock b/Cargo.lock
index d4da9cde..733c26e5 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3223,6 +3223,7 @@ dependencies = [
  "regex",
  "serde",
  "serde_json",
+ "serde_yml",
  "tempfile",
  "thiserror",
  "time",
diff --git a/ssg-metadata/Cargo.toml b/ssg-metadata/Cargo.toml
index 1d5a284a..68f8a72d 100644
--- a/ssg-metadata/Cargo.toml
+++ b/ssg-metadata/Cargo.toml
@@ -36,6 +36,7 @@ thiserror = "1.0"
 tokio = { version = "1.0", features = ["full"] }
 time = "0.3"
 regex = "1.10"
+serde_yml = "0.0.12"
 quick-xml = "0.36"
 
 [build-dependencies]
diff --git a/ssg-metadata/src/error.rs b/ssg-metadata/src/error.rs
index 92c8a722..fe4801d5 100644
--- a/ssg-metadata/src/error.rs
+++ b/ssg-metadata/src/error.rs
@@ -1,3 +1,4 @@
+use serde_yml::Error as SerdeYmlError;
 use thiserror::Error;
 
 /// Custom error types for the ssg-metadata library
@@ -25,7 +26,7 @@ pub enum MetadataError {
 
     /// YAML parsing error
     #[error("YAML parsing error: {0}")]
-    YamlError(#[from] yaml_rust2::ScanError),
+    YamlError(#[from] SerdeYmlError),
 
     /// JSON parsing error
     #[error("JSON parsing error: {0}")]
diff --git a/ssg-metadata/tests/test_error.rs b/ssg-metadata/tests/test_error.rs
index ab955f6a..ae3c4dac 100644
--- a/ssg-metadata/tests/test_error.rs
+++ b/ssg-metadata/tests/test_error.rs
@@ -5,8 +5,11 @@
 
 #[cfg(test)]
 mod tests {
+    use serde_json::Error as JsonError;
+    use serde_yml::Error as YamlError;
     use ssg_metadata::error::MetadataError;
     use std::io;
+    use toml::de::Error as TomlError;
 
     /// Test `ExtractionError` construction.
     ///
@@ -72,4 +75,65 @@ mod tests {
         let error = MetadataError::from(io_error);
         assert_eq!(error.to_string(), "I/O error: File not found");
     }
+
+    /// Test `YamlError` conversion.
+    ///
+    /// This test ensures that a `serde_yml::Error` is correctly converted into the `YamlError` variant.
+    #[test]
+    fn test_yaml_error() {
+        // Malformed YAML content
+        let invalid_yaml = "invalid: yaml: data";
+
+        // Try to parse the invalid YAML, which will trigger a `serde_yml::Error`
+        let yaml_error: Result<serde_yml::Value, YamlError> =
+            serde_yml::from_str(invalid_yaml);
+
+        if let Err(yaml_error) = yaml_error {
+            // Convert the `serde_yml::Error` into `MetadataError`
+            let error = MetadataError::from(yaml_error);
+
+            // Check that the error message is correctly formatted
+            assert!(error.to_string().contains("YAML parsing error"));
+        } else {
+            panic!("Expected YAML parsing error, but got Ok");
+        }
+    }
+
+    /// Test `JsonError` conversion.
+    ///
+    /// This test ensures that a `serde_json::Error` is correctly converted into the `JsonError` variant.
+    #[test]
+    fn test_json_error() {
+        let invalid_json = "{ invalid json }"; // Malformed JSON
+        let json_error: Result<serde_json::Value, JsonError> =
+            serde_json::from_str(invalid_json);
+
+        if let Err(json_error) = json_error {
+            let error = MetadataError::from(json_error);
+            // Check if the error message contains the correct phrase
+            assert!(
+                error.to_string().contains("JSON parsing error"),
+                "Error message should contain 'JSON parsing error'"
+            );
+        } else {
+            panic!("Expected JSON parsing error, but got Ok");
+        }
+    }
+
+    /// Test `TomlError` conversion.
+    ///
+    /// This test ensures that a `toml::de::Error` is correctly converted into the `TomlError` variant.
+    #[test]
+    fn test_toml_error() {
+        let invalid_toml = "invalid = toml"; // Malformed TOML
+        let toml_error: Result<toml::Value, TomlError> =
+            toml::from_str(invalid_toml);
+
+        if let Err(toml_error) = toml_error {
+            let error = MetadataError::from(toml_error);
+            assert!(error.to_string().contains("TOML parsing error"));
+        } else {
+            panic!("Expected TOML parsing error, but got Ok");
+        }
+    }
 }
diff --git a/ssg-metadata/tests/test_metatags.rs b/ssg-metadata/tests/test_metatags.rs
index 5dddf15f..0608400f 100644
--- a/ssg-metadata/tests/test_metatags.rs
+++ b/ssg-metadata/tests/test_metatags.rs
@@ -5,6 +5,8 @@
 #[cfg(test)]
 mod tests {
     use regex::Regex;
+    use ssg_metadata::generate_metatags;
+    use ssg_metadata::MetaTagGroups;
     use std::collections::HashMap;
 
     /// Parses meta tags from an HTML string and returns a HashMap.
@@ -48,4 +50,99 @@ mod tests {
             "Empty meta tags should not be parsed"
         );
     }
+
+    /// Test adding a custom primary meta tag.
+    #[test]
+    fn test_add_custom_primary_tag() {
+        let mut meta_tags = MetaTagGroups::default();
+        meta_tags.add_custom_tag("custom-tag", "custom value");
+
+        assert!(meta_tags.primary.contains("custom-tag"));
+        assert!(meta_tags.primary.contains("custom value"));
+    }
+
+    /// Test adding a custom OpenGraph (og) meta tag.
+    #[test]
+    fn test_add_custom_og_tag() {
+        let mut meta_tags = MetaTagGroups::default();
+        meta_tags.add_custom_tag("og:custom", "custom og value");
+
+        assert!(meta_tags.og.contains("og:custom"));
+        assert!(meta_tags.og.contains("custom og value"));
+    }
+
+    /// Test adding a custom Twitter meta tag.
+    #[test]
+    fn test_add_custom_twitter_tag() {
+        let mut meta_tags = MetaTagGroups::default();
+        meta_tags
+            .add_custom_tag("twitter:custom", "custom twitter value");
+
+        assert!(meta_tags.twitter.contains("twitter:custom"));
+        assert!(meta_tags.twitter.contains("custom twitter value"));
+    }
+
+    /// Test adding a custom Apple meta tag.
+    #[test]
+    fn test_add_custom_apple_tag() {
+        let mut meta_tags = MetaTagGroups::default();
+        meta_tags.add_custom_tag(
+            "apple-mobile-web-app-custom",
+            "custom apple value",
+        );
+
+        assert!(meta_tags
+            .apple
+            .contains("apple-mobile-web-app-custom"));
+        assert!(meta_tags.apple.contains("custom apple value"));
+    }
+
+    /// Test adding a custom Microsoft meta tag.
+    #[test]
+    fn test_add_custom_ms_tag() {
+        let mut meta_tags = MetaTagGroups::default();
+        meta_tags
+            .add_custom_tag("msapplication-custom", "custom ms value");
+
+        assert!(meta_tags.ms.contains("msapplication-custom"));
+        assert!(meta_tags.ms.contains("custom ms value"));
+    }
+
+    /// Test adding multiple custom tags of different types.
+    #[test]
+    fn test_add_multiple_custom_tags() {
+        let mut meta_tags = MetaTagGroups::default();
+        meta_tags.add_custom_tag("custom-primary", "primary value");
+        meta_tags.add_custom_tag("og:custom", "og value");
+        meta_tags.add_custom_tag("twitter:custom", "twitter value");
+        meta_tags.add_custom_tag(
+            "apple-mobile-web-app-custom",
+            "apple value",
+        );
+        meta_tags.add_custom_tag("msapplication-custom", "ms value");
+
+        // Check primary meta tags
+        assert!(meta_tags.primary.contains("<meta name=\"custom-primary\" content=\"primary value\">"),
+        "Primary meta tag should contain 'custom-primary'");
+
+        // Check Open Graph (og) meta tags
+        assert!(
+            meta_tags.og.contains(
+                "<meta name=\"og:custom\" content=\"og value\">"
+            ),
+            "OG meta tag should contain 'og:custom'"
+        );
+
+        // Check Twitter meta tags
+        assert!(meta_tags.twitter.contains("<meta name=\"twitter:custom\" content=\"twitter value\">"),
+        "Twitter meta tag should contain 'twitter:custom'");
+
+        // Check Apple meta tags
+        assert!(meta_tags.apple.contains("<meta name=\"apple-mobile-web-app-custom\" content=\"apple value\">"),
+        "Apple meta tag should contain 'apple-mobile-web-app-custom'");
+
+        // Check Microsoft meta tags
+        assert!(meta_tags.ms.contains("<meta name=\"msapplication-custom\" content=\"ms value\">"),
+        "MS meta tag should contain 'msapplication-custom'");
+    }
 }