diff --git a/app/logical/bigquery_export_service.rb b/app/logical/bigquery_export_service.rb
index 6a0801bd6..6d208a1c1 100644
--- a/app/logical/bigquery_export_service.rb
+++ b/app/logical/bigquery_export_service.rb
@@ -55,20 +55,21 @@ class BigqueryExportService
 
     file = dump_records!
     upload_to_bigquery!(file)
+  ensure
+    file&.close
   end
 
   # Dump the table's records to a gzipped, newline-delimited JSON tempfile.
-  def dump_records!
-    file = Tempfile.new("danbooru-export-dump-", binmode: true)
-    file = Zlib::GzipWriter.new(file)
+  def dump_records!(file = Danbooru::Tempfile.new("danbooru-export-dump-#{model.name}-", binmode: true))
+    gzip = Zlib::GzipWriter.new(file)
 
     CurrentUser.scoped(User.anonymous) do
       records.find_each(batch_size: 5_000) do |record|
-        file.puts(record.to_json)
+        gzip.puts(record.to_json)
       end
     end
 
-    file.close # flush zlib footer
+    gzip.finish
     file
   end
 
diff --git a/app/logical/danbooru/http.rb b/app/logical/danbooru/http.rb
index 849cc38f7..7f7fbb59c 100644
--- a/app/logical/danbooru/http.rb
+++ b/app/logical/danbooru/http.rb
@@ -171,11 +171,11 @@ module Danbooru
       # Download a file from `url` and return a {MediaFile}.
       #
       # @param url [String] the URL to download
-      # @param file [Tempfile] the file to download the URL to
+      # @param file [Danbooru::Tempfile] the file to download the URL to
       # @raise [DownloadError] if the server returns a non-200 OK response
       # @raise [FileTooLargeError] if the file exceeds Danbooru's maximum download size.
       # @return [Array<(HTTP::Response, MediaFile)>] the HTTP response and the downloaded file
-      def download_media(url, file: Tempfile.new("danbooru-download-", binmode: true))
+      def download_media(url, file: Danbooru::Tempfile.new("danbooru-download-#{url.parameterize.truncate(96)}-", binmode: true))
         response = get(url)
 
         raise DownloadError, "#{url} failed with code #{response.status}" if response.status != 200
diff --git a/app/logical/danbooru/tempfile.rb b/app/logical/danbooru/tempfile.rb
new file mode 100644
index 000000000..75891a418
--- /dev/null
+++ b/app/logical/danbooru/tempfile.rb
@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+# Like Tempfile, but delete the tempfile when it's closed.
+#
+# The Tempfile class in the standard library doesn't delete the file immediately when you call `file.close`. Instead you
+# have to call `file.close!` or `file.unlink` to delete the file, or wait until the object gets garbage collected, which
+# can take a long time. This makes it so that Tempfiles are cleaned up immediately on close.
+module Danbooru
+  class Tempfile < ::Tempfile
+    def close(unlink = true)
+      super
+    end
+  end
+end
diff --git a/app/logical/discord_slash_command/tagme_command.rb b/app/logical/discord_slash_command/tagme_command.rb
index 2f610ed9c..b2839a135 100644
--- a/app/logical/discord_slash_command/tagme_command.rb
+++ b/app/logical/discord_slash_command/tagme_command.rb
@@ -52,6 +52,8 @@ class DiscordSlashCommand
           },
         }]
       }
+    ensure
+      preview&.close
     end
 
     def get_last_message_with_url(limit: 10)
diff --git a/app/logical/ffmpeg.rb b/app/logical/ffmpeg.rb
index 0fe3dc3ea..7a3c9c3ab 100644
--- a/app/logical/ffmpeg.rb
+++ b/app/logical/ffmpeg.rb
@@ -22,7 +22,7 @@ class FFmpeg
   #
   # @return [MediaFile] the preview image
   def smart_video_preview
-    vp = Tempfile.new(["video-preview", ".png"], binmode: true)
+    vp = Danbooru::Tempfile.new(["danbooru-video-preview-#{file.md5}-", ".png"], binmode: true)
 
     # https://ffmpeg.org/ffmpeg.html#Main-options
     # https://ffmpeg.org/ffmpeg-filters.html#thumbnail
diff --git a/app/logical/iqdb_client.rb b/app/logical/iqdb_client.rb
index e17adc780..fd007dc2a 100644
--- a/app/logical/iqdb_client.rb
+++ b/app/logical/iqdb_client.rb
@@ -101,6 +101,8 @@ class IqdbClient
       preview = media_file.preview!(Danbooru.config.small_image_width, Danbooru.config.small_image_width)
       file = HTTP::FormData::File.new(preview)
       request(:post, "query", form: { file: file }, params: { limit: limit })
+    ensure
+      preview&.close
     end
 
     # Add a post to IQDB.
diff --git a/app/logical/media_file/image.rb b/app/logical/media_file/image.rb
index 1b41b0f90..9c9cc46c8 100644
--- a/app/logical/media_file/image.rb
+++ b/app/logical/media_file/image.rb
@@ -7,6 +7,11 @@
 class MediaFile::Image < MediaFile
   delegate :thumbnail_image, to: :image
 
+  def close
+    super
+    @preview_frame&.close unless @preview_frame == self
+  end
+
   def dimensions
     image.size
   rescue Vips::Error
@@ -107,7 +112,7 @@ class MediaFile::Image < MediaFile
       resized_image = resized_image.flatten(background: 255)
     end
 
-    output_file = Tempfile.new(["image-preview-#{md5}", ".#{format.to_s}"])
+    output_file = Danbooru::Tempfile.new(["danbooru-image-preview-#{md5}-", ".#{format.to_s}"])
     case format.to_sym
     when :jpeg
       # https://www.libvips.org/API/current/VipsForeignSave.html#vips-jpegsave
@@ -130,14 +135,6 @@ class MediaFile::Image < MediaFile
     preview_frame.resize!(w, h, size: :force, **options)
   end
 
-  def preview_frame
-    if is_animated?
-      FFmpeg.new(self).smart_video_preview
-    else
-      self
-    end
-  end
-
   def is_animated?
     frame_count.to_i > 1
   end
@@ -166,6 +163,8 @@ class MediaFile::Image < MediaFile
     false
   end
 
+  private
+
   # @return [Vips::Image] the Vips image object for the file
   def image
     Vips::Image.new_from_file(file.path, fail: false).autorot
@@ -175,5 +174,15 @@ class MediaFile::Image < MediaFile
     FFmpeg.new(self)
   end
 
-  memoize :image, :video, :preview_frame, :dimensions, :error, :metadata, :is_corrupt?, :is_animated_gif?, :is_animated_png?
+  def preview_frame
+    @preview_frame ||= begin
+      if is_animated?
+        FFmpeg.new(self).smart_video_preview
+      else
+        self
+      end
+    end
+  end
+
+  memoize :image, :video, :dimensions, :error, :metadata, :is_corrupt?, :is_animated_gif?, :is_animated_png?
 end
diff --git a/app/logical/media_file/ugoira.rb b/app/logical/media_file/ugoira.rb
index bf7f10c05..dc68df42e 100644
--- a/app/logical/media_file/ugoira.rb
+++ b/app/logical/media_file/ugoira.rb
@@ -17,8 +17,9 @@ class MediaFile::Ugoira < MediaFile
   end
 
   def close
-    file.close
-    preview_frame.close
+    super
+    @preview_frame&.close
+    # XXX should clean up `convert` too
   end
 
   def metadata
@@ -52,7 +53,7 @@ class MediaFile::Ugoira < MediaFile
     raise RuntimeError, "can't convert ugoira to webm: no ugoira frame data was provided" unless frame_delays.present?
 
     Danbooru::Archive.extract!(file) do |tmpdir, filenames|
-      output_file = Tempfile.new(["ugoira-conversion", ".webm"], binmode: true)
+      output_file = Danbooru::Tempfile.new(["danbooru-ugoira-conversion-#{md5}-", ".webm"], binmode: true)
 
       # Duplicate last frame to avoid it being displayed only for a very short amount of time.
       last_file_name = File.basename(filenames.last)
@@ -90,8 +91,8 @@ class MediaFile::Ugoira < MediaFile
   private
 
   def preview_frame
-    FFmpeg.new(convert).smart_video_preview
+    @preview_frame ||= FFmpeg.new(convert).smart_video_preview
   end
 
-  memoize :preview_frame, :dimensions, :convert, :metadata
+  memoize :dimensions, :convert, :metadata
 end
diff --git a/app/logical/media_file/video.rb b/app/logical/media_file/video.rb
index 615c88302..997ad8897 100644
--- a/app/logical/media_file/video.rb
+++ b/app/logical/media_file/video.rb
@@ -10,6 +10,11 @@ class MediaFile::Video < MediaFile
     :audio_stream, :audio_streams, :silence_duration, :silence_percentage, :average_loudness,
     :peak_loudness, :loudness_range, :error, to: :video
 
+  def close
+    super
+    @preview_frame&.close
+  end
+
   def dimensions
     [video.width, video.height]
   end
@@ -65,8 +70,8 @@ class MediaFile::Video < MediaFile
   end
 
   def preview_frame
-    video.smart_video_preview
+    @preview_frame ||= video.smart_video_preview
   end
 
-  memoize :video, :preview_frame, :dimensions, :metadata, :duration, :has_audio?
+  memoize :video, :dimensions, :metadata, :duration, :has_audio?
 end
diff --git a/app/logical/post_replacement_processor.rb b/app/logical/post_replacement_processor.rb
index 3891f2256..3816b2e8d 100644
--- a/app/logical/post_replacement_processor.rb
+++ b/app/logical/post_replacement_processor.rb
@@ -53,6 +53,8 @@ class PostReplacementProcessor
   rescue Exception => exception
     replacement.errors.add(:base, exception.message)
     raise ActiveRecord::Rollback
+  ensure
+    media_file&.close
   end
 
   def rescale_notes(post)
diff --git a/app/logical/storage_manager/rclone.rb b/app/logical/storage_manager/rclone.rb
index de2ffc249..c9eb40d4f 100644
--- a/app/logical/storage_manager/rclone.rb
+++ b/app/logical/storage_manager/rclone.rb
@@ -27,7 +27,7 @@ class StorageManager::Rclone < StorageManager
   end
 
   def open(path)
-    file = Tempfile.new(binmode: true)
+    file = Danbooru::Tempfile.new(binmode: true)
     rclone "copyto", key(path), file.path
     file
   end
diff --git a/app/models/media_asset.rb b/app/models/media_asset.rb
index a09576efd..0e6682515 100644
--- a/app/models/media_asset.rb
+++ b/app/models/media_asset.rb
@@ -68,6 +68,8 @@ class MediaAsset < ApplicationRecord
       file = convert_file(original_file)
       storage_service.store(file, file_path)
       backup_storage_service.store(file, file_path)
+    ensure
+      file&.close
     end
 
     def trash_file!
diff --git a/app/models/upload_media_asset.rb b/app/models/upload_media_asset.rb
index a2e6dfb91..6da34154b 100644
--- a/app/models/upload_media_asset.rb
+++ b/app/models/upload_media_asset.rb
@@ -112,6 +112,8 @@ class UploadMediaAsset < ApplicationRecord
     update!(status: :active)
   rescue Exception => e
     update!(status: :failed, error: e.message)
+  ensure
+    media_file&.close
   end
 
   def update_upload_status
diff --git a/test/unit/storage_manager_test.rb b/test/unit/storage_manager_test.rb
index 1dfce4e9e..794cbaf82 100644
--- a/test/unit/storage_manager_test.rb
+++ b/test/unit/storage_manager_test.rb
@@ -2,7 +2,7 @@ require 'test_helper'
 
 class StorageManagerTest < ActiveSupport::TestCase
   def tempfile(data)
-    file = Tempfile.new
+    file = Danbooru::Tempfile.new
     file.write(data)
     file.flush
     file