diff --git a/src-tauri/src/services/cache_manager.rs b/src-tauri/src/services/cache_manager.rs
new file mode 100644
index 0000000..c30284a
--- /dev/null
+++ b/src-tauri/src/services/cache_manager.rs
@@ -0,0 +1,207 @@
+// Future: used by project file save/load and cache Tauri commands.
+#![allow(dead_code)]
+
+use crate::models::{ThumbnailSpritesheet, WaveformTiers};
+use serde::{Deserialize, Serialize};
+use sha2::{Digest, Sha256};
+use std::path::PathBuf;
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct CacheManifest {
+    pub version: u32,
+    pub source_url: String,
+    pub title: String,
+    pub duration: f64,
+    pub fps: f64,
+    pub created_at: String,
+    pub last_accessed_at: String,
+    pub waveform_tiers: Option<WaveformTiers>,
+    pub keyframe_positions: Vec<f64>,
+    pub thumbnail_spritesheets: Vec<ThumbnailSpritesheet>,
+    pub caption_file_path: Option<String>,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct CacheStats {
+    pub entry_count: usize,
+    pub total_bytes: u64,
+}
+
+/// First 16 hex characters of the SHA-256 hash of the URL.
+pub fn url_hash(url: &str) -> String {
+    let mut hasher = Sha256::new();
+    hasher.update(url.as_bytes());
+    let result = hasher.finalize();
+    result[..8]
+        .iter()
+        .map(|b| format!("{b:02x}"))
+        .collect::<String>()
+}
+
+pub fn cache_base_dir() -> PathBuf {
+    dirs::data_dir()
+        .unwrap_or_else(|| PathBuf::from("."))
+        .join("gui-video-clipper")
+        .join("cache")
+}
+
+pub fn cache_dir_for_url(url: &str) -> PathBuf {
+    cache_base_dir().join(url_hash(url))
+}
+
+pub fn thumbnail_cache_dir(url: &str) -> PathBuf {
+    cache_dir_for_url(url).join("thumbnails")
+}
+
+pub fn caption_cache_dir(url: &str) -> PathBuf {
+    cache_dir_for_url(url).join("captions")
+}
+
+fn manifest_path(url: &str) -> PathBuf {
+    cache_dir_for_url(url).join("manifest.json")
+}
+
+fn now_iso8601() -> String {
+    // Use a simple UTC timestamp without pulling in chrono
+    let duration = std::time::SystemTime::now()
+        .duration_since(std::time::UNIX_EPOCH)
+        .unwrap_or_default();
+    let secs = duration.as_secs();
+    // Format as ISO 8601 — good enough for cache timestamps
+    format!("{secs}")
+}
+
+pub fn load_manifest(url: &str) -> Option<CacheManifest> {
+    let path = manifest_path(url);
+    if !path.is_file() {
+        return None;
+    }
+    let data = std::fs::read_to_string(&path).ok()?;
+    let mut manifest: CacheManifest = serde_json::from_str(&data).ok()?;
+    // Update last-accessed timestamp
+    manifest.last_accessed_at = now_iso8601();
+    if let Ok(json) = serde_json::to_string_pretty(&manifest) {
+        let _ = std::fs::write(&path, json);
+    }
+    Some(manifest)
+}
+
+pub fn save_manifest(url: &str, manifest: &CacheManifest) -> Result<(), String> {
+    let dir = cache_dir_for_url(url);
+    std::fs::create_dir_all(&dir)
+        .map_err(|e| format!("Failed to create cache dir: {e}"))?;
+    let path = dir.join("manifest.json");
+    let json = serde_json::to_string_pretty(manifest)
+        .map_err(|e| format!("Failed to serialize manifest: {e}"))?;
+    std::fs::write(&path, json)
+        .map_err(|e| format!("Failed to write manifest: {e}"))?;
+    eprintln!("[video-clipper:cache] saved manifest to '{}'", path.display());
+    Ok(())
+}
+
+pub fn clear_cache_entry(url: &str) -> Result<(), String> {
+    let dir = cache_dir_for_url(url);
+    if dir.is_dir() {
+        std::fs::remove_dir_all(&dir)
+            .map_err(|e| format!("Failed to remove cache entry: {e}"))?;
+        eprintln!("[video-clipper:cache] cleared entry at '{}'", dir.display());
+    }
+    Ok(())
+}
+
+pub fn clear_all_cache() -> Result<(), String> {
+    let base = cache_base_dir();
+    if base.is_dir() {
+        std::fs::remove_dir_all(&base)
+            .map_err(|e| format!("Failed to remove cache dir: {e}"))?;
+        eprintln!("[video-clipper:cache] cleared all cache at '{}'", base.display());
+    }
+    Ok(())
+}
+
+pub fn get_cache_stats() -> Result<CacheStats, String> {
+    let base = cache_base_dir();
+    if !base.is_dir() {
+        return Ok(CacheStats {
+            entry_count: 0,
+            total_bytes: 0,
+        });
+    }
+
+    let mut entry_count = 0usize;
+    let mut total_bytes = 0u64;
+
+    let entries = std::fs::read_dir(&base)
+        .map_err(|e| format!("Failed to read cache dir: {e}"))?;
+
+    for entry in entries.flatten() {
+        let path = entry.path();
+        if path.is_dir() {
+            entry_count += 1;
+            total_bytes += dir_size(&path);
+        }
+    }
+
+    Ok(CacheStats {
+        entry_count,
+        total_bytes,
+    })
+}
+
+fn dir_size(path: &std::path::Path) -> u64 {
+    let mut total = 0u64;
+    if let Ok(entries) = std::fs::read_dir(path) {
+        for entry in entries.flatten() {
+            let p = entry.path();
+            if p.is_file() {
+                total += std::fs::metadata(&p).map(|m| m.len()).unwrap_or(0);
+            } else if p.is_dir() {
+                total += dir_size(&p);
+            }
+        }
+    }
+    total
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_url_hash_length() {
+        let hash = url_hash("https://youtube.com/watch?v=abc123");
+        assert_eq!(hash.len(), 16);
+    }
+
+    #[test]
+    fn test_url_hash_deterministic() {
+        let url = "https://youtube.com/watch?v=abc123";
+        assert_eq!(url_hash(url), url_hash(url));
+    }
+
+    #[test]
+    fn test_url_hash_different_urls() {
+        let a = url_hash("https://youtube.com/watch?v=abc");
+        let b = url_hash("https://youtube.com/watch?v=xyz");
+        assert_ne!(a, b);
+    }
+
+    #[test]
+    fn test_cache_dir_for_url_contains_hash() {
+        let url = "https://youtube.com/watch?v=test";
+        let dir = cache_dir_for_url(url);
+        let hash = url_hash(url);
+        assert!(dir.to_string_lossy().contains(&hash));
+    }
+
+    #[test]
+    fn test_thumbnail_cache_dir_is_subdir() {
+        let url = "https://example.com/video";
+        let base = cache_dir_for_url(url);
+        let thumbs = thumbnail_cache_dir(url);
+        assert!(thumbs.starts_with(&base));
+        assert!(thumbs.to_string_lossy().ends_with("thumbnails"));
+    }
+}
diff --git a/src-tauri/src/services/mod.rs b/src-tauri/src/services/mod.rs
index 3ae3f92..517b364 100644
--- a/src-tauri/src/services/mod.rs
+++ b/src-tauri/src/services/mod.rs
@@ -1,3 +1,4 @@
+pub mod cache_manager;
 pub mod clip_exporter;
 pub mod dependency_manager;
 pub mod download_manager;