diff --git a/Cargo.lock b/Cargo.lock
index 64d7c7ea..eeefe65b 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2505,6 +2505,7 @@ dependencies = [
  "security-framework",
  "serde",
  "serde_json",
+ "sha2",
  "strum",
  "strum_macros",
  "tempfile",
diff --git a/Cargo.toml b/Cargo.toml
index 20b1c77b..60cf1f1a 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -52,6 +52,7 @@ url = "2.5.2"
 urlencoding = "2.1.3"
 uuid = { version = "1.10.0", features = ["v4"] }
 security-framework = "2.11.0"
+sha2 = "0.10.8"
 
 [profile.small]
 inherits = 'release'
diff --git a/crates/notedeck/Cargo.toml b/crates/notedeck/Cargo.toml
index 31bdfba2..b8138641 100644
--- a/crates/notedeck/Cargo.toml
+++ b/crates/notedeck/Cargo.toml
@@ -22,6 +22,7 @@ serde = { workspace = true }
 hex = { workspace = true }
 thiserror = { workspace = true }
 puffin = { workspace = true, optional = true }
+sha2 = { workspace = true }
 
 [dev-dependencies]
 tempfile = { workspace = true }
diff --git a/crates/notedeck/src/imgcache.rs b/crates/notedeck/src/imgcache.rs
index 4a78fc00..9cbe31a1 100644
--- a/crates/notedeck/src/imgcache.rs
+++ b/crates/notedeck/src/imgcache.rs
@@ -5,9 +5,13 @@ use poll_promise::Promise;
 use egui::ColorImage;
 
 use std::collections::HashMap;
-use std::fs::File;
+use std::fs::{create_dir_all, File};
 
+use hex::ToHex;
+use sha2::Digest;
 use std::path;
+use std::path::PathBuf;
+use tracing::warn;
 
 pub type ImageCacheValue = Promise<Result<TextureHandle>>;
 pub type ImageCacheMap = HashMap<String, ImageCacheValue>;
@@ -46,6 +50,9 @@ impl ImageCache {
 
     pub fn write(cache_dir: &path::Path, url: &str, data: ColorImage) -> Result<()> {
         let file_path = cache_dir.join(Self::key(url));
+        if let Some(p) = file_path.parent() {
+            create_dir_all(p)?;
+        }
         let file = File::options()
             .write(true)
             .create(true)
@@ -64,7 +71,51 @@ impl ImageCache {
     }
 
     pub fn key(url: &str) -> String {
-        base32::encode(base32::Alphabet::Crockford, url.as_bytes())
+        let k: String = sha2::Sha256::digest(url.as_bytes()).encode_hex();
+        PathBuf::from(&k[0..2])
+            .join(&k[2..4])
+            .join(k)
+            .to_string_lossy()
+            .to_string()
+    }
+
+    /// Migrate from base32 encoded url to sha256 url + sub-dir structure
+    pub fn migrate_v0(&self) -> Result<()> {
+        for file in std::fs::read_dir(&self.cache_dir)? {
+            let file = if let Ok(f) = file {
+                f
+            } else {
+                // not sure how this could fail, skip entry
+                continue;
+            };
+            if !file.path().is_file() {
+                continue;
+            }
+            let old_filename = file.file_name().to_string_lossy().to_string();
+            let old_url = if let Some(u) =
+                base32::decode(base32::Alphabet::Crockford, &old_filename)
+                    .and_then(|s| String::from_utf8(s).ok())
+            {
+                u
+            } else {
+                warn!("Invalid base32 filename: {}", &old_filename);
+                continue;
+            };
+            let new_path = self.cache_dir.join(Self::key(&old_url));
+            if let Some(p) = new_path.parent() {
+                create_dir_all(p)?;
+            }
+
+            if let Err(e) = std::fs::rename(file.path(), &new_path) {
+                warn!(
+                    "Failed to migrate file from {} to {}: {:?}",
+                    file.path().display(),
+                    new_path.display(),
+                    e
+                );
+            }
+        }
+        Ok(())
     }
 
     pub fn map(&self) -> &ImageCacheMap {
diff --git a/crates/notedeck_chrome/src/app.rs b/crates/notedeck_chrome/src/app.rs
index 6cc6435b..c420d0d3 100644
--- a/crates/notedeck_chrome/src/app.rs
+++ b/crates/notedeck_chrome/src/app.rs
@@ -207,6 +207,11 @@ impl Notedeck {
         let tabs = Tabs::new(None);
         let app_rect_handler = AppSizeHandler::new(&path);
 
+        // migrate
+        if let Err(e) = img_cache.migrate_v0() {
+            error!("error migrating image cache: {e}");
+        }
+
         Self {
             ndb,
             img_cache,