diff --git a/src/commands/watch.rs b/src/commands/watch.rs
index ddfdbea..542937d 100644
--- a/src/commands/watch.rs
+++ b/src/commands/watch.rs
@@ -1,4 +1,4 @@
-use std::{collections::BinaryHeap, io::Read, time::Duration};
+use std::{collections::BinaryHeap, hash::Hasher, io::Read, time::Duration};
 
 use smol::Timer;
 use wl_clipboard_rs::{
@@ -15,36 +15,9 @@ use wl_clipboard_rs::{
 use crate::{
   clipboard::{self, ClipboardData, get_serving_pid},
   db::{SqliteClipboardDb, nonblocking::AsyncClipboardDb},
+  hash::Fnv1aHasher,
 };
 
-/// FNV-1a hasher for deterministic hashing across process runs.
-/// Unlike `DefaultHasher` (`SipHash`), this produces stable hashes.
-struct Fnv1aHasher {
-  state: u64,
-}
-
-impl Fnv1aHasher {
-  const FNV_OFFSET: u64 = 0xCBF29CE484222325;
-  const FNV_PRIME: u64 = 0x100000001B3;
-
-  fn new() -> Self {
-    Self {
-      state: Self::FNV_OFFSET,
-    }
-  }
-
-  fn write(&mut self, bytes: &[u8]) {
-    for byte in bytes {
-      self.state ^= u64::from(*byte);
-      self.state = self.state.wrapping_mul(Self::FNV_PRIME);
-    }
-  }
-
-  fn finish(&self) -> u64 {
-    self.state
-  }
-}
-
 /// Wrapper to provide [`Ord`] implementation for `f64` by negating values.
 /// This allows [`BinaryHeap`], which is a max-heap, to function as a min-heap.
 /// Also see:
diff --git a/src/db/mod.rs b/src/db/mod.rs
index 441495f..f907b3b 100644
--- a/src/db/mod.rs
+++ b/src/db/mod.rs
@@ -11,6 +11,10 @@ use std::{
 
 pub mod nonblocking;
 
+use std::hash::Hasher;
+
+use crate::hash::Fnv1aHasher;
+
 /// Cache for process scanning results to avoid expensive `/proc` reads on every
 /// store operation. TTL of 5 seconds balances freshness with performance.
 struct ProcessCache {
@@ -66,35 +70,6 @@ impl ProcessCache {
   }
 }
 
-/// FNV-1a hasher for deterministic hashing across process runs.
-/// Unlike `DefaultHasher` (`SipHash` with random seed), this produces stable
-/// hashes.
-pub struct Fnv1aHasher {
-  state: u64,
-}
-
-impl Fnv1aHasher {
-  const FNV_OFFSET: u64 = 0xCBF29CE484222325;
-  const FNV_PRIME: u64 = 0x100000001B3;
-
-  pub fn new() -> Self {
-    Self {
-      state: Self::FNV_OFFSET,
-    }
-  }
-
-  pub fn write(&mut self, bytes: &[u8]) {
-    for byte in bytes {
-      self.state ^= u64::from(*byte);
-      self.state = self.state.wrapping_mul(Self::FNV_PRIME);
-    }
-  }
-
-  pub fn finish(&self) -> u64 {
-    self.state
-  }
-}
-
 use base64::prelude::*;
 use log::{debug, error, info, warn};
 use mime_sniffer::MimeTypeSniffer;
diff --git a/src/hash.rs b/src/hash.rs
new file mode 100644
index 0000000..f017a51
--- /dev/null
+++ b/src/hash.rs
@@ -0,0 +1,101 @@
+/// FNV-1a hasher for deterministic hashing across process runs.
+///
+/// Unlike `std::collections::hash_map::DefaultHasher` (which uses SipHash
+/// with a random seed), this produces stable hashes suitable for persistent
+/// storage and cross-process comparison.
+///
+/// # Example
+///
+/// ```
+/// use std::hash::Hasher;
+///
+/// use stash::hash::Fnv1aHasher;
+///
+/// let mut hasher = Fnv1aHasher::new();
+/// hasher.write(b"hello");
+/// let hash = hasher.finish();
+/// ```
+#[derive(Clone, Copy, Debug)]
+pub struct Fnv1aHasher {
+  state: u64,
+}
+
+impl Fnv1aHasher {
+  const FNV_OFFSET: u64 = 0xCBF29CE484222325;
+  const FNV_PRIME: u64 = 0x100000001B3;
+
+  /// Creates a new hasher initialized with the FNV-1a offset basis.
+  #[must_use]
+  pub fn new() -> Self {
+    Self {
+      state: Self::FNV_OFFSET,
+    }
+  }
+}
+
+impl Default for Fnv1aHasher {
+  fn default() -> Self {
+    Self::new()
+  }
+}
+
+impl std::hash::Hasher for Fnv1aHasher {
+  fn write(&mut self, bytes: &[u8]) {
+    for byte in bytes {
+      self.state ^= u64::from(*byte);
+      self.state = self.state.wrapping_mul(Self::FNV_PRIME);
+    }
+  }
+
+  fn finish(&self) -> u64 {
+    self.state
+  }
+}
+
+#[cfg(test)]
+mod tests {
+  use std::hash::Hasher;
+
+  use super::*;
+
+  #[test]
+  fn test_fnv1a_basic() {
+    let mut hasher = Fnv1aHasher::new();
+    hasher.write(b"hello");
+    // FNV-1a hash for "hello" (little-endian u64)
+    assert_eq!(hasher.finish(), 0xA430D84680AABD0B);
+  }
+
+  #[test]
+  fn test_fnv1a_empty() {
+    let hasher = Fnv1aHasher::new();
+    // Empty input should return offset basis
+    assert_eq!(hasher.finish(), Fnv1aHasher::FNV_OFFSET);
+  }
+
+  #[test]
+  fn test_fnv1a_deterministic() {
+    // Same input must produce same hash
+    let mut h1 = Fnv1aHasher::new();
+    let mut h2 = Fnv1aHasher::new();
+    h1.write(b"test data");
+    h2.write(b"test data");
+    assert_eq!(h1.finish(), h2.finish());
+  }
+
+  #[test]
+  fn test_default_trait() {
+    let h1 = Fnv1aHasher::new();
+    let h2 = Fnv1aHasher::default();
+    assert_eq!(h1.finish(), h2.finish());
+  }
+
+  #[test]
+  fn test_copy_trait() {
+    let mut hasher = Fnv1aHasher::new();
+    hasher.write(b"data");
+    let copied = hasher;
+    // Both should have same state after copy
+    assert_eq!(hasher.finish(), copied.finish());
+  }
+}
diff --git a/src/main.rs b/src/main.rs
index 53ed1c9..32c271d 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,6 +1,7 @@
 mod clipboard;
 mod commands;
 mod db;
+mod hash;
 mod mime;
 mod multicall;