diff --git a/src/library/entry.cr b/src/library/entry.cr
index 77af3e5..ef0556d 100644
--- a/src/library/entry.cr
+++ b/src/library/entry.cr
@@ -15,9 +15,9 @@ abstract class Entry
 
   def self.new(ctx : YAML::ParseContext, node : YAML::Nodes::Node)
     # TODO: check node? and select proper subclass
-    ZippedEntry.new ctx, node
+    ArchiveEntry.new ctx, node
   rescue e
-    DirectoryEntry.new ctx, node
+    DirEntry.new ctx, node
   end
 
   def build_json(*, slim = false)
@@ -230,7 +230,7 @@ abstract class Entry
   abstract def examine : Bool?
 end
 
-class ZippedEntry < Entry
+class ArchiveEntry < Entry
   include YAML::Serializable
 
   getter zip_path : String
@@ -341,7 +341,7 @@ class ZippedEntry < Entry
   end
 end
 
-class DirectoryEntry < Entry
+class DirEntry < Entry
   include YAML::Serializable
 
   getter dir_path : String
@@ -364,7 +364,7 @@ class DirectoryEntry < Entry
       return
     end
 
-    unless DirectoryEntry.validate_directory_entry @dir_path
+    unless DirEntry.validate_directory_entry @dir_path
       @err_msg = "Directory #{@dir_path} is not valid directory entry."
       Logger.warn "#{@err_msg} Please make sure the " \
                   "directory has valid images."
@@ -441,7 +441,7 @@ class DirectoryEntry < Entry
   def examine : Bool
     existence = File.exists? @dir_path
     return false unless existence
-    files = DirectoryEntry.get_valid_files @dir_path
+    files = DirEntry.get_valid_files @dir_path
     signature = Dir.directory_entry_signature @dir_path
     existence = files.size > 0 && @signature == signature
     @sorted_files = nil unless existence
@@ -454,12 +454,12 @@ class DirectoryEntry < Entry
   def sorted_files
     cached_sorted_files = @sorted_files
     return cached_sorted_files if cached_sorted_files
-    @sorted_files = DirectoryEntry.get_valid_files_sorted @dir_path
+    @sorted_files = DirEntry.get_valid_files_sorted @dir_path
     @sorted_files.not_nil!
   end
 
   def self.validate_directory_entry(dir_path)
-    files = DirectoryEntry.get_valid_files dir_path
+    files = DirEntry.get_valid_files dir_path
     files.size > 0
   end
 
@@ -477,7 +477,7 @@ class DirectoryEntry < Entry
   end
 
   def self.get_valid_files_sorted(dir_path)
-    files = DirectoryEntry.get_valid_files dir_path
+    files = DirEntry.get_valid_files dir_path
     files.sort! { |a, b| compare_numerically a, b }
   end
 end
diff --git a/src/library/title.cr b/src/library/title.cr
index f3b4866..3f30490 100644
--- a/src/library/title.cr
+++ b/src/library/title.cr
@@ -53,14 +53,14 @@ class Title
           Library.default.title_hash[title.id] = title
           @title_ids << title.id
         end
-        if DirectoryEntry.validate_directory_entry path
-          entry = DirectoryEntry.new path, self
+        if DirEntry.validate_directory_entry path
+          entry = DirEntry.new path, self
           @entries << entry if entry.pages > 0 || entry.err_msg
         end
         next
       end
       if is_supported_file path
-        entry = ZippedEntry.new path, self
+        entry = ArchiveEntry.new path, self
         @entries << entry if entry.pages > 0 || entry.err_msg
       end
     end
@@ -146,8 +146,8 @@ class Title
       path = File.join dir, fn
       if File.directory? path
         unless remained_entry_paths.includes? path
-          if DirectoryEntry.validate_directory_entry path
-            entry = DirectoryEntry.new path, self
+          if DirEntry.validate_directory_entry path
+            entry = DirEntry.new path, self
             if entry.pages > 0 || entry.err_msg
               @entries << entry
               is_entries_added = true
@@ -181,7 +181,7 @@ class Title
       end
       if is_supported_file path
         next if remained_entry_paths.includes? path
-        entry = ZippedEntry.new path, self
+        entry = ArchiveEntry.new path, self
         if entry.pages > 0 || entry.err_msg
           @entries << entry
           is_entries_added = true
diff --git a/src/routes/api.cr b/src/routes/api.cr
index bf2c4c9..509f13d 100644
--- a/src/routes/api.cr
+++ b/src/routes/api.cr
@@ -142,7 +142,7 @@ struct APIRouter
           env.response.status_code = 304
           ""
         else
-          if entry.is_a? DirectoryEntry
+          if entry.is_a? DirEntry
             cache_control = "no-cache, max-age=86400"
           else
             cache_control = "public, max-age=86400"
@@ -1143,7 +1143,7 @@ struct APIRouter
         entry = title.get_entry eid
         raise "Entry ID `#{eid}` of `#{title.title}` not found" if entry.nil?
 
-        if entry.is_a? DirectoryEntry
+        if entry.is_a? DirEntry
           file_hash = Digest::SHA1.hexdigest(entry.path + entry.mtime.to_s + entry.size)
         else
           file_hash = Digest::SHA1.hexdigest(entry.path + entry.mtime.to_s)
@@ -1154,7 +1154,7 @@ struct APIRouter
           send_text env, ""
         else
           sizes = entry.page_dimensions
-          if entry.is_a? DirectoryEntry
+          if entry.is_a? DirEntry
             cache_control = "no-cache, max-age=86400"
           else
             cache_control = "public, max-age=86400"
diff --git a/src/util/signature.cr b/src/util/signature.cr
index 904d4e6..b5fe781 100644
--- a/src/util/signature.cr
+++ b/src/util/signature.cr
@@ -64,7 +64,7 @@ class Dir
         path = File.join dirname, fn
         if File.directory? path
           signatures << Dir.contents_signature path, cache
-          if DirectoryEntry.validate_directory_entry path
+          if DirEntry.validate_directory_entry path
             signatures << fn
           end
         else
@@ -84,7 +84,7 @@ class Dir
     return cache[dirname + "?entry"] if cache[dirname + "?entry"]?
     Fiber.yield
     signatures = [] of String
-    image_files = DirectoryEntry.get_valid_files_sorted dirname
+    image_files = DirEntry.get_valid_files_sorted dirname
     if image_files.size > 0
       image_files.each do |path|
         signatures << File.signature(path).to_s