diff --git a/Cargo.lock b/Cargo.lock
index e3751d8..8677cc6 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1964,6 +1964,7 @@ version = "0.0.0"
 dependencies = [
  "itertools",
  "openidconnect",
+ "serde",
  "serde_json",
  "thiserror",
  "url",
diff --git a/crates/ezidam/src/error.rs b/crates/ezidam/src/error.rs
index 70e0eb4..96ea2ef 100644
--- a/crates/ezidam/src/error.rs
+++ b/crates/ezidam/src/error.rs
@@ -43,4 +43,8 @@ impl Error {
     pub fn not_found<M: std::fmt::Display>(value: M) -> Self {
         Self::new(Status::NotFound, value)
     }
+
+    pub fn bad_request<M: std::fmt::Display>(value: M) -> Self {
+        Self::new(Status::BadRequest, value)
+    }
 }
diff --git a/crates/ezidam/src/routes/oauth.rs b/crates/ezidam/src/routes/oauth.rs
index ee35d6d..1d81552 100644
--- a/crates/ezidam/src/routes/oauth.rs
+++ b/crates/ezidam/src/routes/oauth.rs
@@ -28,7 +28,15 @@ async fn authorize_page(
     flash: Option<FlashMessage<'_>>,
     auth_request: AuthenticationRequest<'_>,
 ) -> Result<Template> {
-    // TODO: parse "scope" and "response_type" -> from openid local crate
+    // Check for valid response types
+    openid::parse_response_types(auth_request.response_type)
+        .ok_or_else(|| Error::bad_request("Bad response types"))?;
+
+    // Check for supported scopes
+    if !openid::SupportedScopes::check_supported_scopes(auth_request.scope) {
+        return Err(Error::bad_request("Invalid scopes"));
+    }
+
     let mut transaction = db.begin().await?;
     // TODO: wrap checking in function?
 
@@ -38,7 +46,7 @@ async fn authorize_page(
         auth_request.redirect_uri,
     )
     .await?
-    .ok_or_else(|| Error::not_found(auth_request.client_id))?;
+    .ok_or_else(|| Error::bad_request("Invalid application"))?;
 
     let settings = Settings::get(&mut transaction).await?;
 
diff --git a/crates/openid/Cargo.toml b/crates/openid/Cargo.toml
index e4e5578..f924df9 100644
--- a/crates/openid/Cargo.toml
+++ b/crates/openid/Cargo.toml
@@ -6,6 +6,7 @@ edition = "2021"
 [dependencies]
 thiserror = { workspace = true }
 url = { workspace = true }
+serde = { workspace = true }
 serde_json = { workspace = true }
 openidconnect = { version = "3.0.0-alpha.1", default-features = false }
 itertools = "0.10.5"
\ No newline at end of file
diff --git a/crates/openid/src/lib.rs b/crates/openid/src/lib.rs
index 8383ca0..4c8d809 100644
--- a/crates/openid/src/lib.rs
+++ b/crates/openid/src/lib.rs
@@ -6,7 +6,7 @@ mod scopes;
 /// Exports
 pub use configuration::configuration;
 pub use error::Error;
-pub use response_types::supported_response_types;
+pub use response_types::{parse_response_types, supported_response_types};
 pub use scopes::SupportedScopes;
 
 /// Type exports
diff --git a/crates/openid/src/response_types.rs b/crates/openid/src/response_types.rs
index 9dbc5ba..e2b22c1 100644
--- a/crates/openid/src/response_types.rs
+++ b/crates/openid/src/response_types.rs
@@ -9,3 +9,51 @@ pub fn supported_response_types() -> Vec<ResponseTypes<CoreResponseType>> {
         ResponseTypes::new(vec![CoreResponseType::Token, CoreResponseType::IdToken]), // Other flows including hybrid flows may also be specified here.
     ]
 }
+
+pub fn parse_response_types(raw: &str) -> Option<Vec<CoreResponseType>> {
+    if raw.is_empty() {
+        return None;
+    }
+
+    let list = raw
+        .split_whitespace()
+        .flat_map(|s| {
+            // Convert string to json to deserialize with serde_json
+            let value_json = format!("\"{}\"", s);
+            let deserializer = &mut serde_json::Deserializer::from_str(&value_json);
+            // Attempt to deserialize into CoreResponseType
+            serde::Deserialize::deserialize(deserializer).ok()
+        })
+        // If any fails, return None
+        .collect::<Vec<_>>();
+
+    // If vec is empty or contains `Extension`, return None
+    if list.is_empty()
+        || list
+            .iter()
+            .any(|variant| matches!(variant, CoreResponseType::Extension(_)))
+    {
+        None
+    } else {
+        Some(list)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::parse_response_types;
+
+    #[test]
+    fn check_valid() {
+        assert!(parse_response_types("code id_token").is_some());
+        assert!(parse_response_types("code token").is_some());
+        assert!(parse_response_types("code token id_token").is_some());
+    }
+
+    #[test]
+    fn check_invalid() {
+        assert!(parse_response_types("").is_none());
+        assert!(parse_response_types("test").is_none());
+        assert!(parse_response_types("abc def code ghi id_token").is_none());
+    }
+}
diff --git a/crates/openid/src/scopes.rs b/crates/openid/src/scopes.rs
index c35cfaf..6e7062e 100644
--- a/crates/openid/src/scopes.rs
+++ b/crates/openid/src/scopes.rs
@@ -1,5 +1,6 @@
 use itertools::Itertools;
 use openidconnect::Scope;
+use std::collections::HashSet;
 
 pub struct SupportedScopes(pub Vec<Scope>);
 
@@ -7,6 +8,16 @@ impl SupportedScopes {
     pub fn url_format() -> String {
         Self::default().0.iter().map(|s| s.as_str()).join(" ")
     }
+    pub fn check_supported_scopes(scopes: &str) -> bool {
+        if scopes.is_empty() {
+            return false;
+        }
+
+        let list = Self::default();
+        let scope_set: &HashSet<_> = &list.0.iter().map(|s| s.as_str()).collect();
+        let requested_scopes: HashSet<_> = scopes.split_whitespace().collect();
+        requested_scopes.is_subset(scope_set)
+    }
 }
 
 impl Default for SupportedScopes {
@@ -18,3 +29,25 @@ impl Default for SupportedScopes {
         ])
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::SupportedScopes;
+
+    #[test]
+    fn check_valid() {
+        assert!(SupportedScopes::check_supported_scopes("openid"));
+        assert!(SupportedScopes::check_supported_scopes("profile email"));
+        assert!(SupportedScopes::check_supported_scopes("email openid"));
+    }
+
+    #[test]
+    fn check_invalid() {
+        assert!(!SupportedScopes::check_supported_scopes(""));
+        assert!(!SupportedScopes::check_supported_scopes("openid abc"));
+        assert!(!SupportedScopes::check_supported_scopes("test"));
+        assert!(!SupportedScopes::check_supported_scopes(
+            "email testing wrong profile"
+        ));
+    }
+}