diff --git a/fuzzers/tinyinst_simple/src/main.rs b/fuzzers/tinyinst_simple/src/main.rs
index c029423b11..bc50e0d98b 100644
--- a/fuzzers/tinyinst_simple/src/main.rs
+++ b/fuzzers/tinyinst_simple/src/main.rs
@@ -40,7 +40,7 @@ fn main() {
     // let args = vec!["test.exe".to_string(), "-f".to_string(), "@@".to_string()];
 
     let observer = unsafe { ListObserver::new("cov", &mut COVERAGE) };
-    let mut feedback = ListFeedback::with_observer(&observer);
+    let mut feedback = ListFeedback::new(&observer);
     #[cfg(windows)]
     let mut shmem_provider = Win32ShMemProvider::new().unwrap();
 
diff --git a/libafl/src/feedbacks/list.rs b/libafl/src/feedbacks/list.rs
new file mode 100644
index 0000000000..8cacc507ba
--- /dev/null
+++ b/libafl/src/feedbacks/list.rs
@@ -0,0 +1,172 @@
+use alloc::string::{String, ToString};
+use core::{fmt::Debug, hash::Hash, marker::PhantomData};
+
+use hashbrown::HashSet;
+use libafl_bolts::{Error, HasRefCnt, Named};
+use serde::{de::DeserializeOwned, Deserialize, Serialize};
+
+use crate::{
+    events::EventFirer,
+    executors::ExitKind,
+    feedbacks::Feedback,
+    observers::{ListObserver, ObserversTuple},
+    state::{HasNamedMetadata, State},
+};
+
+/// The metadata to remember past observed value
+#[derive(Default, Serialize, Deserialize, Clone, Debug)]
+#[serde(bound = "T: DeserializeOwned")]
+#[cfg_attr(
+    any(not(feature = "serdeany_autoreg"), miri),
+    allow(clippy::unsafe_derive_deserialize)
+)]
+pub struct ListFeedbackMetadata<T>
+where
+    T: Default + Copy + 'static + Serialize + Eq + Hash,
+{
+    /// Contains the information of past observed set of values.
+    pub set: HashSet<T>,
+    /// A refcount used to know when we can remove this metadata
+    pub tcref: isize,
+}
+
+impl<T> ListFeedbackMetadata<T>
+where
+    T: Default + Copy + 'static + Serialize + Eq + Hash,
+{
+    /// The constructor
+    #[must_use]
+    pub fn new() -> Self {
+        Self {
+            set: HashSet::<T>::new(),
+            tcref: 0,
+        }
+    }
+
+    /// Reset the inner hashset
+    pub fn reset(&mut self) -> Result<(), Error> {
+        self.set.clear();
+        Ok(())
+    }
+}
+
+impl<T> HasRefCnt for ListFeedbackMetadata<T>
+where
+    T: Default + Copy + 'static + Serialize + Eq + Hash,
+{
+    fn refcnt(&self) -> isize {
+        self.tcref
+    }
+
+    fn refcnt_mut(&mut self) -> &mut isize {
+        &mut self.tcref
+    }
+}
+
+/// Consider interesting a testcase if the list in `ListObserver` is not empty.
+#[derive(Clone, Debug)]
+pub struct ListFeedback<T>
+where
+    T: Hash + Eq,
+{
+    name: String,
+    observer_name: String,
+    novelty: HashSet<T>,
+    phantom: PhantomData<T>,
+}
+
+libafl_bolts::impl_serdeany!(
+    ListFeedbackMetadata<T: Debug + Default + Copy + 'static + Serialize + DeserializeOwned + Eq + Hash>,
+    <u8>,<u16>,<u32>,<u64>,<i8>,<i16>,<i32>,<i64>,<bool>,<char>,<usize>
+);
+
+impl<S, T> Feedback<S> for ListFeedback<T>
+where
+    S: State + HasNamedMetadata,
+    T: Debug + Serialize + Hash + Eq + DeserializeOwned + Default + Copy + 'static,
+{
+    fn init_state(&mut self, state: &mut S) -> Result<(), Error> {
+        // eprintln!("self.name {:#?}", &self.name);
+        state.add_named_metadata(&self.name, ListFeedbackMetadata::<T>::default());
+        Ok(())
+    }
+    #[allow(clippy::wrong_self_convention)]
+    fn is_interesting<EM, OT>(
+        &mut self,
+        state: &mut S,
+        _manager: &mut EM,
+        _input: &S::Input,
+        observers: &OT,
+        _exit_kind: &ExitKind,
+    ) -> Result<bool, Error>
+    where
+        EM: EventFirer<State = S>,
+        OT: ObserversTuple<S>,
+    {
+        // TODO Replace with match_name_type when stable
+        let observer = observers
+            .match_name::<ListObserver<T>>(&self.observer_name)
+            .unwrap();
+        // TODO register the list content in a testcase metadata
+        self.novelty.clear();
+        // can't fail
+        let history_set = state
+            .named_metadata_map_mut()
+            .get_mut::<ListFeedbackMetadata<T>>(&self.name)
+            .unwrap();
+        for v in observer.list() {
+            if !history_set.set.contains(v) {
+                self.novelty.insert(*v);
+            }
+        }
+        Ok(!self.novelty.is_empty())
+    }
+
+    fn append_metadata<EM, OT>(
+        &mut self,
+        state: &mut S,
+        _manager: &mut EM,
+        _observers: &OT,
+        _testcase: &mut crate::corpus::Testcase<<S>::Input>,
+    ) -> Result<(), Error>
+    where
+        OT: ObserversTuple<S>,
+        EM: EventFirer<State = S>,
+    {
+        let history_set = state
+            .named_metadata_map_mut()
+            .get_mut::<ListFeedbackMetadata<T>>(&self.name)
+            .unwrap();
+
+        for v in &self.novelty {
+            history_set.set.insert(*v);
+        }
+        Ok(())
+    }
+}
+
+impl<T> Named for ListFeedback<T>
+where
+    T: Debug + Serialize + Hash + Eq + DeserializeOwned,
+{
+    #[inline]
+    fn name(&self) -> &str {
+        self.name.as_str()
+    }
+}
+
+impl<T> ListFeedback<T>
+where
+    T: Debug + Serialize + Hash + Eq + DeserializeOwned,
+{
+    /// Creates a new [`ListFeedback`], deciding if the given [`ListObserver`] value of a run is interesting.
+    #[must_use]
+    pub fn new(observer: &ListObserver<T>) -> Self {
+        Self {
+            name: observer.name().to_string(),
+            observer_name: observer.name().to_string(),
+            novelty: HashSet::<T>::new(),
+            phantom: PhantomData,
+        }
+    }
+}
diff --git a/libafl/src/feedbacks/map.rs b/libafl/src/feedbacks/map.rs
index f9a3d778b4..f70b87c413 100644
--- a/libafl/src/feedbacks/map.rs
+++ b/libafl/src/feedbacks/map.rs
@@ -28,9 +28,6 @@ use crate::{
     Error,
 };
 
-/// The prefix of the metadata names
-pub const MAPFEEDBACK_PREFIX: &str = "mapfeedback_metadata_";
-
 /// A [`MapFeedback`] that implements the AFL algorithm using an [`OrReducer`] combining the bits for the history map and the bit from ``HitcountsMapObserver``.
 pub type AflMapFeedback<O, S, T> = MapFeedback<DifferentIsNovel, O, OrReducer, S, T>;
 
@@ -700,7 +697,7 @@ where
         Self {
             indexes: false,
             novelties: None,
-            name: MAPFEEDBACK_PREFIX.to_string() + map_observer.name(),
+            name: map_observer.name().to_string(),
             observer_name: map_observer.name().to_string(),
             stats_name: create_stats_name(map_observer.name()),
             phantom: PhantomData,
@@ -713,7 +710,7 @@ where
         Self {
             indexes: track_indexes,
             novelties: if track_novelties { Some(vec![]) } else { None },
-            name: MAPFEEDBACK_PREFIX.to_string() + map_observer.name(),
+            name: map_observer.name().to_string(),
             observer_name: map_observer.name().to_string(),
             stats_name: create_stats_name(map_observer.name()),
             phantom: PhantomData,
diff --git a/libafl/src/feedbacks/mod.rs b/libafl/src/feedbacks/mod.rs
index d030a75b3b..ce63e5f58a 100644
--- a/libafl/src/feedbacks/mod.rs
+++ b/libafl/src/feedbacks/mod.rs
@@ -25,6 +25,8 @@ pub use new_hash_feedback::NewHashFeedbackMetadata;
 pub mod nautilus;
 pub mod transferred;
 
+/// The module for list feedback
+pub mod list;
 use alloc::string::{String, ToString};
 use core::{
     fmt::{self, Debug, Formatter},
@@ -32,6 +34,7 @@ use core::{
 };
 
 use libafl_bolts::Named;
+pub use list::*;
 #[cfg(feature = "nautilus")]
 pub use nautilus::*;
 use serde::{Deserialize, Serialize};
@@ -40,7 +43,7 @@ use crate::{
     corpus::Testcase,
     events::EventFirer,
     executors::ExitKind,
-    observers::{ListObserver, ObserversTuple, TimeObserver},
+    observers::{ObserversTuple, TimeObserver},
     state::State,
     Error,
 };
@@ -972,79 +975,6 @@ impl TimeFeedback {
     }
 }
 
-/// Consider interesting a testcase if the list in `ListObserver` is not empty.
-#[derive(Serialize, Deserialize, Clone, Debug)]
-pub struct ListFeedback<T>
-where
-    T: Debug + Serialize + serde::de::DeserializeOwned,
-{
-    name: String,
-    last_addr: usize,
-    phantom: PhantomData<T>,
-}
-
-impl<S, T> Feedback<S> for ListFeedback<T>
-where
-    S: State,
-    T: Debug + Serialize + serde::de::DeserializeOwned,
-{
-    #[allow(clippy::wrong_self_convention)]
-    fn is_interesting<EM, OT>(
-        &mut self,
-        _state: &mut S,
-        _manager: &mut EM,
-        _input: &S::Input,
-        observers: &OT,
-        _exit_kind: &ExitKind,
-    ) -> Result<bool, Error>
-    where
-        EM: EventFirer<State = S>,
-        OT: ObserversTuple<S>,
-    {
-        // TODO Replace with match_name_type when stable
-        let observer = observers
-            .match_name::<ListObserver<T>>(self.name())
-            .unwrap();
-        // TODO register the list content in a testcase metadata
-        Ok(!observer.list().is_empty())
-    }
-}
-
-impl<T> Named for ListFeedback<T>
-where
-    T: Debug + Serialize + serde::de::DeserializeOwned,
-{
-    #[inline]
-    fn name(&self) -> &str {
-        self.name.as_str()
-    }
-}
-
-impl<T> ListFeedback<T>
-where
-    T: Debug + Serialize + serde::de::DeserializeOwned,
-{
-    /// Creates a new [`ListFeedback`], deciding if the value of a [`ListObserver`] with the given `name` of a run is interesting.
-    #[must_use]
-    pub fn new(name: &'static str) -> Self {
-        Self {
-            name: name.to_string(),
-            last_addr: 0,
-            phantom: PhantomData,
-        }
-    }
-
-    /// Creates a new [`TimeFeedback`], deciding if the given [`ListObserver`] value of a run is interesting.
-    #[must_use]
-    pub fn with_observer(observer: &ListObserver<T>) -> Self {
-        Self {
-            name: observer.name().to_string(),
-            last_addr: 0,
-            phantom: PhantomData,
-        }
-    }
-}
-
 /// The [`ConstFeedback`] reports the same value, always.
 /// It can be used to enable or disable feedback results through composition.
 #[derive(Serialize, Deserialize, Clone, Copy, Debug, PartialEq, Eq)]
diff --git a/libafl/src/observers/list.rs b/libafl/src/observers/list.rs
new file mode 100644
index 0000000000..d9cc467a20
--- /dev/null
+++ b/libafl/src/observers/list.rs
@@ -0,0 +1,73 @@
+use alloc::{
+    string::{String, ToString},
+    vec::Vec,
+};
+use core::fmt::Debug;
+
+use libafl_bolts::{ownedref::OwnedMutPtr, Error, Named};
+use serde::{Deserialize, Serialize};
+
+use crate::{inputs::UsesInput, observers::Observer};
+
+/// A simple observer with a list of things.
+#[derive(Serialize, Deserialize, Debug)]
+#[serde(bound = "T: serde::de::DeserializeOwned")]
+#[allow(clippy::unsafe_derive_deserialize)]
+pub struct ListObserver<T>
+where
+    T: Debug + Serialize,
+{
+    name: String,
+    /// The list
+    list: OwnedMutPtr<Vec<T>>,
+}
+
+impl<T> ListObserver<T>
+where
+    T: Debug + Serialize + serde::de::DeserializeOwned,
+{
+    /// Creates a new [`ListObserver`] with the given name.
+    ///
+    /// # Safety
+    /// Will dereference the list.
+    /// The list may not move in memory.
+    #[must_use]
+    pub unsafe fn new(name: &'static str, list: *mut Vec<T>) -> Self {
+        Self {
+            name: name.to_string(),
+            list: OwnedMutPtr::Ptr(list),
+        }
+    }
+
+    /// Get a list ref
+    #[must_use]
+    pub fn list(&self) -> &Vec<T> {
+        self.list.as_ref()
+    }
+
+    /// Get a list mut
+    #[must_use]
+    pub fn list_mut(&mut self) -> &mut Vec<T> {
+        self.list.as_mut()
+    }
+}
+
+impl<S, T> Observer<S> for ListObserver<T>
+where
+    S: UsesInput,
+    T: Debug + Serialize + serde::de::DeserializeOwned,
+{
+    fn pre_exec(&mut self, _state: &mut S, _input: &S::Input) -> Result<(), Error> {
+        self.list.as_mut().clear();
+        Ok(())
+    }
+}
+
+impl<T> Named for ListObserver<T>
+where
+    T: Debug + Serialize + serde::de::DeserializeOwned,
+{
+    fn name(&self) -> &str {
+        &self.name
+    }
+}
diff --git a/libafl/src/observers/mod.rs b/libafl/src/observers/mod.rs
index 69f73d7066..2a5f904d83 100644
--- a/libafl/src/observers/mod.rs
+++ b/libafl/src/observers/mod.rs
@@ -20,17 +20,17 @@ pub mod concolic;
 
 pub mod value;
 
-use alloc::{
-    string::{String, ToString},
-    vec::Vec,
-};
+/// List observer
+pub mod list;
+use alloc::string::{String, ToString};
 use core::{fmt::Debug, time::Duration};
 #[cfg(feature = "std")]
 use std::time::Instant;
 
 #[cfg(feature = "no_std")]
 use libafl_bolts::current_time;
-use libafl_bolts::{ownedref::OwnedMutPtr, tuples::MatchName, Named};
+use libafl_bolts::{tuples::MatchName, Named};
+pub use list::*;
 use serde::{Deserialize, Serialize};
 pub use value::*;
 
@@ -526,73 +526,11 @@ where
 {
 }
 
-/// A simple observer with a list of things.
-#[derive(Serialize, Deserialize, Debug)]
-#[serde(bound = "T: serde::de::DeserializeOwned")]
-#[allow(clippy::unsafe_derive_deserialize)]
-pub struct ListObserver<T>
-where
-    T: Debug + Serialize,
-{
-    name: String,
-    /// The list
-    list: OwnedMutPtr<Vec<T>>,
-}
-
-impl<T> ListObserver<T>
-where
-    T: Debug + Serialize + serde::de::DeserializeOwned,
-{
-    /// Creates a new [`ListObserver`] with the given name.
-    ///
-    /// # Safety
-    /// Will dereference the list.
-    /// The list may not move in memory.
-    #[must_use]
-    pub unsafe fn new(name: &'static str, list: *mut Vec<T>) -> Self {
-        Self {
-            name: name.to_string(),
-            list: OwnedMutPtr::Ptr(list),
-        }
-    }
-
-    /// Get a list ref
-    #[must_use]
-    pub fn list(&self) -> &Vec<T> {
-        self.list.as_ref()
-    }
-
-    /// Get a list mut
-    #[must_use]
-    pub fn list_mut(&mut self) -> &mut Vec<T> {
-        self.list.as_mut()
-    }
-}
-
-impl<S, T> Observer<S> for ListObserver<T>
-where
-    S: UsesInput,
-    T: Debug + Serialize + serde::de::DeserializeOwned,
-{
-    fn pre_exec(&mut self, _state: &mut S, _input: &S::Input) -> Result<(), Error> {
-        self.list.as_mut().clear();
-        Ok(())
-    }
-}
-
-impl<T> Named for ListObserver<T>
-where
-    T: Debug + Serialize + serde::de::DeserializeOwned,
-{
-    fn name(&self) -> &str {
-        &self.name
-    }
-}
-
 /// `Observer` Python bindings
 #[cfg(feature = "python")]
 #[allow(missing_docs)]
 pub mod pybind {
+    use alloc::vec::Vec;
     use core::ptr;
     use std::cell::UnsafeCell;
 
@@ -603,7 +541,7 @@ pub mod pybind {
     use pyo3::prelude::*;
     use serde::{Deserialize, Serialize};
 
-    use super::{Debug, Observer, ObserversTuple, String, Vec};
+    use super::{Debug, Observer, ObserversTuple, String};
     use crate::{
         executors::{pybind::PythonExitKind, ExitKind},
         inputs::{BytesInput, HasBytesVec},
diff --git a/libafl_libfuzzer/libafl_libfuzzer_runtime/src/report.rs b/libafl_libfuzzer/libafl_libfuzzer_runtime/src/report.rs
index ed50a571a6..0384c78ebe 100644
--- a/libafl_libfuzzer/libafl_libfuzzer_runtime/src/report.rs
+++ b/libafl_libfuzzer/libafl_libfuzzer_runtime/src/report.rs
@@ -3,7 +3,7 @@ use std::ffi::c_int;
 use libafl::{
     events::{ProgressReporter, SimpleEventManager},
     executors::HasObservers,
-    feedbacks::{MapFeedbackMetadata, MAPFEEDBACK_PREFIX},
+    feedbacks::MapFeedbackMetadata,
     inputs::UsesInput,
     monitors::SimpleMonitor,
     stages::{HasCurrentStage, StagesTuple},
@@ -35,7 +35,7 @@ where
     ST: StagesTuple<E, EM, S, F>,
 {
     let meta = state
-        .named_metadata::<MapFeedbackMetadata<u8>>(&(MAPFEEDBACK_PREFIX.to_string() + "edges"))
+        .named_metadata::<MapFeedbackMetadata<u8>>("edges")
         .unwrap();
     let observed = meta.history_map.iter().filter(|&&e| e != 0).count();
     let total = meta.history_map.len();