diff --git a/CHANGES.md b/CHANGES.md
index ad094cea..ab4e81bc 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -14,6 +14,10 @@
 
 * Kithe derivatves store created at in shrine metadata for derivative, as UTC iso8601 string https://github.com/sciencehistory/kithe/pull/190
 
+* `Attacher.define_derivative` block can now take an optional `add_metadata` keyword arg with a hash that can be mutated to set metadata on derivative. https://github.com/sciencehistory/kithe/pull/193  https://github.com/sciencehistory/kithe/blob/master/guides/derivatives.md#specifying-metadata-for-defined-derivatives
+
+* Built-in derivative transformers will supply some creation tooling metadata if given the `add_metadata` argument. If you are using these, you might have to change the signatures on your `define_derivative` calls to take advantage of new functionality. https://github.com/sciencehistory/kithe/pull/193  https://github.com/sciencehistory/kithe/blob/master/guides/derivatives.md#kithe-provided-derivative-creation-tools
+
 ### Fixed
 
 * Use up-to-date vips CLI thumbnail recommendations, without deprecated options Should be no change to thumbnails generated, just differnet form of args. https://github.com/sciencehistory/kithe/pull/192  https://github.com/sciencehistory/kithe/pull/194
diff --git a/app/derivative_transformers/kithe/ffmpeg_extract_jpg.rb b/app/derivative_transformers/kithe/ffmpeg_extract_jpg.rb
index f9d92623..a64c3da3 100644
--- a/app/derivative_transformers/kithe/ffmpeg_extract_jpg.rb
+++ b/app/derivative_transformers/kithe/ffmpeg_extract_jpg.rb
@@ -8,6 +8,10 @@ module Kithe
   # @example tempfile = FfmpegExtractJpg.new.call(url)
   # @example tempfile = FfmpegExtractJpg.new(start_seconds: 60).call(shrine_uploaded_file)
   # @example tempfile = FfmpegExtractJpg.new(start_seconds: 10, width_pixels: 420).call(shrine_uploaded_file)
+  #
+  # @example you can also provide a Hash which will be mutated with metadata relevant to
+  # the derivative created, ffmpeg version and args:
+  #     @example tempfile = FfmpegExtractJpg.new(start_seconds: 10, width_pixels: 420).call(shrine_uploaded_file, add_metadata: my_hash)
   class FfmpegExtractJpg
     class_attribute :ffmpeg_command, default: "ffmpeg"
     attr_reader :start_seconds, :frame_sample_size, :width_pixels
@@ -43,19 +47,19 @@ def initialize(start_seconds: 0, frame_sample_size: false, width_pixels: nil)
     #   Most efficient is if we have a remote URL to give ffmpeg, one way or another!
     #
     # @returns [Tempfile] jpg extracted from movie
-    def call(input_arg)
+    def call(input_arg, add_metadata:nil)
       if input_arg.kind_of?(Shrine::UploadedFile)
         if input_arg.respond_to?(:url) && input_arg.url&.start_with?(/https?\:/)
-          _call(input_arg.url)
+          _call(input_arg.url, add_metadata: add_metadata)
         else
           Shrine.with_file(input_arg) do |local_file|
-            _call(local_file.path)
+            _call(local_file.path, add_metadata: add_metadata)
           end
         end
       elsif input_arg.respond_to?(:path)
-        _call(input_arg.path)
+        _call(input_arg.path, add_metadata: add_metadata)
       else
-        _call(input_arg.to_s)
+        _call(input_arg.to_s, add_metadata: add_metadata)
       end
     end
 
@@ -67,14 +71,26 @@ def call(input_arg)
     # @param ffmpeg_source_arg [String] filepath or URL. ffmpeg can take urls, which
     # can be very efficient.
     #
+    # @param add_metadata [Hash], optional, if provided will be filled out with metadata
+    # relevant to the derivative created -- ffmpeg version and args.
+    #
     # @returns Tempfile pointing to a thumbnail
-    def _call(ffmpeg_source_arg)
+    def _call(ffmpeg_source_arg, add_metadata: nil)
       tempfile = Tempfile.new(['temp_deriv', ".jpg"])
 
       ffmpeg_args = produce_ffmpeg_args(input_arg: ffmpeg_source_arg, output_path: tempfile.path)
 
       TTY::Command.new(printer: :null).run(*ffmpeg_args)
 
+      if add_metadata
+        add_metadata[:ffmpeg_command] = ffmpeg_args.join(" ")
+
+        `#{ffmpeg_command} -version` =~ /ffmpeg version (\d+\.\d+.*) Copyright/
+        if $1
+          add_metadata[:ffmpeg_version] = $1
+        end
+      end
+
       return tempfile
     rescue StandardError => e
       tempfile.unlink if tempfile
diff --git a/app/derivative_transformers/kithe/ffmpeg_transformer.rb b/app/derivative_transformers/kithe/ffmpeg_transformer.rb
index 6f170042..b198f6c1 100644
--- a/app/derivative_transformers/kithe/ffmpeg_transformer.rb
+++ b/app/derivative_transformers/kithe/ffmpeg_transformer.rb
@@ -39,13 +39,23 @@ def transform_arguments
     end
 
     # Will raise TTY::Command::ExitError if the ffmpeg returns non-null.
-    def call(original_file)
+    def call(original_file, add_metadata: nil)
       tempfile = Tempfile.new(['temp_deriv', ".#{@output_suffix}"])
       # -y tells ffmpeg to overwrite the abovementioned tempfile (still empty)
       # with the output of ffmpeg.
       ffmpeg_args =  [ffmpeg_command, "-y", "-i", original_file.path]
       ffmpeg_args += transform_arguments + [tempfile.path]
-      TTY::Command.new(printer: :null).run(*ffmpeg_args)
+      out, err = TTY::Command.new(printer: :null).run(*ffmpeg_args)
+
+      if add_metadata
+        add_metadata[:ffmpeg_command] = ffmpeg_args.join(" ")
+
+        `#{ffmpeg_command} -version` =~ /ffmpeg version (\d+\.\d+.*) Copyright/
+        if $1
+          add_metadata[:ffmpeg_version] = $1
+        end
+      end
+
       return tempfile
     end
   end
diff --git a/app/derivative_transformers/kithe/vips_cli_image_to_jpeg.rb b/app/derivative_transformers/kithe/vips_cli_image_to_jpeg.rb
index 2d4d101b..afddb638 100644
--- a/app/derivative_transformers/kithe/vips_cli_image_to_jpeg.rb
+++ b/app/derivative_transformers/kithe/vips_cli_image_to_jpeg.rb
@@ -19,8 +19,8 @@ module Kithe
   # built for use with kithe derivatives transformations, eg:
   #
   #     class Asset < KitheAsset
-  #       define_derivative(thumb) do |original_file|
-  #         Kithe::VipsCliImageToJpeg.new(max_width: 100, thumbnail_mode: true).call(original_file)
+  #       Attacher.define_derivative(:thumb) do |original_file, add_metadata:|
+  #         Kithe::VipsCliImageToJpeg.new(max_width: 100, thumbnail_mode: true).call(original_file, add_metadata: add_metadata)
   #       end
   #     end
   #
@@ -50,7 +50,7 @@ def initialize(max_width:nil, jpeg_q: 85, thumbnail_mode: false)
     end
 
     # Will raise TTY::Command::ExitError if the external Vips command returns non-null.
-    def call(original_file)
+    def call(original_file, add_metadata: nil)
       tempfile = Tempfile.new(["kithe_vips_cli_image_to_jpeg", ".jpg"])
 
       vips_args = []
@@ -62,7 +62,7 @@ def call(original_file)
         # really huge one million pixels so it should not come into play, and
         # we're constraining proportionally by width.
         # https://github.com/jcupitt/libvips/issues/781
-        vips_args.concat [vips_thumbnail_command, original_file.path]
+        vips_args.concat [vips_thumbnail_command, "--version", original_file.path]
         vips_args.concat maybe_profile_normalization_args
         vips_args.concat ["--size", "#{max_width}x65500"]
         vips_args.concat ["-o", "#{tempfile.path}#{vips_jpg_params}"]
@@ -75,7 +75,16 @@ def call(original_file)
         vips_args.concat ["#{tempfile.path}#{vips_jpg_params}"]
       end
 
-      TTY::Command.new(printer: :null).run(*vips_args)
+      out, err = TTY::Command.new(printer: :null).run(*vips_args)
+
+      if add_metadata
+        add_metadata[:vips_command] = vips_args.join(" ")
+
+        out =~ /vips[ \-](\d+\.\d+\.\d+.*$)/
+        if $1
+          add_metadata[:vips_version] = $1
+        end
+      end
 
       return tempfile
     end
diff --git a/app/models/kithe/asset/derivative_definition.rb b/app/models/kithe/asset/derivative_definition.rb
index b9bc96aa..66b4e274 100644
--- a/app/models/kithe/asset/derivative_definition.rb
+++ b/app/models/kithe/asset/derivative_definition.rb
@@ -9,12 +9,32 @@ def initialize(key:, proc:, content_type: nil, default_create: true)
     @proc = proc
   end
 
+  # @return [Hash] add_metadata hash of metadata to add to derivative on storage
   def call(original_file:,attacher:)
+    add_metadata = {}
+    kwargs = {}
+
     if proc_accepts_keyword?(:attacher)
-      proc.call(original_file, attacher: attacher)
+      kwargs[:attacher] = attacher
+    end
+
+    if proc_accepts_keyword?(:add_metadata)
+      kwargs[:add_metadata] = add_metadata
+    end
+
+    return_val = if kwargs.present?
+      proc.call(original_file, **kwargs)
     else
       proc.call(original_file)
     end
+
+    # Save in context to later write to actual stored derivative metadata
+    if add_metadata.present?
+      attacher.context[:add_metadata] ||= {}
+      attacher.context[:add_metadata][key] = add_metadata
+    end
+
+    return_val
   end
 
   # Do content-type restrictions defined for this definition match a given asset?
diff --git a/guides/derivatives.md b/guides/derivatives.md
index 895825e3..3866fefc 100644
--- a/guides/derivatives.md
+++ b/guides/derivatives.md
@@ -103,6 +103,19 @@ class Asset < Kithe::Asset
 end
 ```
 
+### Specifying metadata for defined derivatives
+
+You can also optionally provide an `add_metadata` keyword arg to your block. It will be given a mutable hash that you can mutate to specify JSON-compatible metadata that will be stored with the derivative.
+
+```ruby
+class MyAssetUploader < Kithe::AssetUploader
+  Attacher.define_derivative(:thumb_small) do |original_file, add_metadata:|
+    add_metadata[:my_key] = "my value"
+
+    anything_that_returns_io_like_object(original_file)
+  end
+end
+```
 
 ### Kithe-provided derivative-creation tools
 
@@ -115,8 +128,8 @@ Which can create a resized JPG from an image input, using a shell out to the `vi
 
 ```ruby
 class Asset < Kithe::Asset
-  define_derivative(:download_small) do |original_file|
-    Kithe::VipsCliImageToJpeg.new(max_width: 500).call(original_file)
+  define_derivative(:download_small) do |original_file, add_metadata:|
+    Kithe::VipsCliImageToJpeg.new(max_width: 500).call(original_file, add_metadata: add_metadata)
   end
 end
 ```
@@ -125,8 +138,8 @@ If you pass `thumbnail_mode: true` when instantiating Kithe::VipsCliImageToJpeg,
 
 ```ruby
 class Asset < Kithe::Asset
-  define_derivative(:thumb_small, content_type: "image") do |original_file|
-    Kithe::VipsCliImageToJpeg.new(max_width: 500, thumbnail_mode: true).call(original_file)
+  define_derivative(:thumb_small, content_type: "image") do |original_file, add_metadata:|
+    Kithe::VipsCliImageToJpeg.new(max_width: 500, thumbnail_mode: true).call(original_file, add_metadata: add_metadata)
   end
 end
 ```
@@ -138,18 +151,18 @@ Which creates audio files from any audio file original, using a shell out to the
 
 ```ruby
 # Create a stereo 128k mp3 derivative. output_suffix is the only mandatory argument.
-define_derivative('mp3', content_type: "audio") do |original_file|
-  Kithe::FfmpegTransformer.new(bitrate: '128k', output_suffix: 'mp3').call(original_file)
+define_derivative('mp3', content_type: "audio") do |original_file, add_metadata:|
+  Kithe::FfmpegTransformer.new(bitrate: '128k', output_suffix: 'mp3').call(original_file, add_metadata: add_metadata)
 end
 
 # A mono webm file at only 64k:
-define_derivative('webm', content_type: "audio") do |original_file|
-  Kithe::FfmpegTransformer.new(bitrate: '64k', force_mono: true, output_suffix: 'webm').call(original_file)
+define_derivative('webm', content_type: "audio") do |original_file, add_metadata:|
+  Kithe::FfmpegTransformer.new(bitrate: '64k', force_mono: true, output_suffix: 'webm').call(original_file, add_metadata: add_metadata)
 end
 
 # libopus is used by default for webm conversions, but you could specify another codec:
-define_derivative('webm', content_type: "audio") do |original_file|
-  Kithe::FfmpegTransformer.new(output_suffix: 'webm', audio_codec: 'libopencore-amrwb').call(original_file)
+define_derivative('webm', content_type: "audio") do |original_file, add_metadata:|
+  Kithe::FfmpegTransformer.new(output_suffix: 'webm', audio_codec: 'libopencore-amrwb').call(original_file, add_metadata: add_metadata)
 end
 ```
 
@@ -163,7 +176,7 @@ However, to take advantage of this feature, avoiding a download, you'd have to w
 complex code. Same if you want to produce multiple resolution thumbnails. This isn't yet fully documented, but be aware of the existence of this service.
 
 ```ruby
-image_tmp_file = Kithe::FfmpegExtractJpg.new(start_seconds: start_seconds).call(original)
+image_tmp_file = Kithe::FfmpegExtractJpg.new(start_seconds: start_seconds).call(original, add_metadata: add_metadata)
 ```
 
 ## Manually triggering creaton of derivatives from definitions
diff --git a/lib/shrine/plugins/kithe_derivatives.rb b/lib/shrine/plugins/kithe_derivatives.rb
index 9c2c91a1..5c5a5145 100644
--- a/lib/shrine/plugins/kithe_derivatives.rb
+++ b/lib/shrine/plugins/kithe_derivatives.rb
@@ -32,9 +32,13 @@ def self.load_dependencies(uploader, *)
 
       module InstanceMethods
 
-        # Override to fix "filename" metadata to be something reasonable, regardless
+        # 1. Override to fix "filename" metadata to be something reasonable, regardless
         # of what if anything was the filename of the IO being attached. shrine S3 will
-        # insist on setting a default content-disposition with this filename.
+        # insist on setting a default content-disposition with this filename, so we
+        # can use that.
+        #
+        # 2. Set any specified derivative metadata on derivative. Specified add_metadata
+        # found in context.
         def extract_metadata(io, derivative:nil, **context)
           result = super
 
@@ -43,9 +47,13 @@ def extract_metadata(io, derivative:nil, **context)
             result["filename"] = "#{context[:record].friendlier_id}_#{derivative}.#{extension}"
           end
 
-          # Add timestamp for derivatives please
+          # If derivative, add timestamp and any specified extra data
           if derivative
             result["created_at"] ||= Time.current.utc.iso8601.to_s
+
+            if (metadata = context.dig(:add_metadata, derivative)).present?
+              result.merge!(metadata.stringify_keys)
+            end
           end
 
           result
diff --git a/spec/derivative_transformers/ffmpeg_extract_jpg_spec.rb b/spec/derivative_transformers/ffmpeg_extract_jpg_spec.rb
index 7d61a9d0..52135b41 100644
--- a/spec/derivative_transformers/ffmpeg_extract_jpg_spec.rb
+++ b/spec/derivative_transformers/ffmpeg_extract_jpg_spec.rb
@@ -20,6 +20,16 @@
       expect(result).to be_kind_of(Tempfile)
       expect(Marcel::MimeType.for(StringIO.new(result.read))).to eq "image/jpeg"
     end
+
+    it "sets add_metadata" do
+      add_metadata = {}
+
+      extractor = Kithe::FfmpegExtractJpg.new(frame_sample_size: 300)
+      extractor.call(video_path, add_metadata: add_metadata)
+
+      expect(add_metadata[:ffmpeg_version]).to match /\d+\.\d+/
+      expect(add_metadata[:ffmpeg_command]).to match /ffmpeg -y -i .*\.jpg/
+    end
   end
 
   describe "from File" do
@@ -32,6 +42,15 @@
       expect(result).to be_kind_of(Tempfile)
       expect(Marcel::MimeType.for(StringIO.new(result.read))).to eq "image/jpeg"
     end
+
+    it "sets add_metadata" do
+      add_metadata = {}
+
+      Kithe::FfmpegExtractJpg.new.call(video_file, add_metadata: add_metadata)
+
+      expect(add_metadata[:ffmpeg_version]).to match /\d+\.\d+/
+      expect(add_metadata[:ffmpeg_command]).to match /ffmpeg -y -i .*\.jpg/
+    end
   end
 
   describe "from Shrine::UploadedFile without good url" do
@@ -52,6 +71,15 @@
       expect(result).to be_kind_of(Tempfile)
       expect(Marcel::MimeType.for(StringIO.new(result.read))).to eq "image/jpeg"
     end
+
+    it "sets add_metadata" do
+      add_metadata = {}
+
+      Kithe::FfmpegExtractJpg.new.call(uploaded_file_obj, add_metadata: add_metadata)
+
+      expect(add_metadata[:ffmpeg_version]).to match /\d+\.\d+/
+      expect(add_metadata[:ffmpeg_command]).to match /ffmpeg -y -i .*\.jpg/
+    end
   end
 
   describe "from Shrine::UploadedFile with good url" do
@@ -80,6 +108,19 @@
 
       result = Kithe::FfmpegExtractJpg.new.call(uploaded_file_obj)
     end
+
+    it "sets add_metadata" do
+      add_metadata = {}
+
+      expect_any_instance_of(TTY::Command).to receive(:run) do |instance, *args|
+        expect(args[0..3]).to eq ["ffmpeg", "-y", "-i", url]
+      end
+
+      Kithe::FfmpegExtractJpg.new.call(uploaded_file_obj, add_metadata: add_metadata)
+
+      expect(add_metadata[:ffmpeg_version]).to match /\d+\.\d+/
+      expect(add_metadata[:ffmpeg_command]).to match /ffmpeg -y -i .*\.jpg/
+    end
   end
 
 
@@ -95,5 +136,18 @@
 
       result = Kithe::FfmpegExtractJpg.new.call(url)
     end
+
+    it "sets add_metadata" do
+      add_metadata = {}
+
+      expect_any_instance_of(TTY::Command).to receive(:run) do |instance, *args|
+        expect(args[0..3]).to eq ["ffmpeg", "-y", "-i", url]
+      end
+
+      Kithe::FfmpegExtractJpg.new.call(url, add_metadata: add_metadata)
+
+      expect(add_metadata[:ffmpeg_version]).to match /\d+\.\d+/
+      expect(add_metadata[:ffmpeg_command]).to match /ffmpeg -y -i .*\.jpg/
+    end
   end
 end
diff --git a/spec/derivative_transformers/ffmpeg_transformer_spec.rb b/spec/derivative_transformers/ffmpeg_transformer_spec.rb
index c88ca38a..79769b7a 100644
--- a/spec/derivative_transformers/ffmpeg_transformer_spec.rb
+++ b/spec/derivative_transformers/ffmpeg_transformer_spec.rb
@@ -85,4 +85,16 @@
       output.close!
     end
   end
+
+  describe "ffmpeg command metadata" do
+    it "is provided when arg is given" do
+      add_metadata = {}
+
+      instance = described_class.new(output_suffix: 'mp3', force_mono: true, bitrate: '32k')
+      output = instance.call(input_file, add_metadata: add_metadata)
+
+      expect(add_metadata[:ffmpeg_version]).to match /\d+\.\d+/
+      expect(add_metadata[:ffmpeg_command]).to match /ffmpeg -y -i .*\.mp3/
+    end
+  end
 end
diff --git a/spec/derivative_transformers/vips_cli_image_to_jpeg_spec.rb b/spec/derivative_transformers/vips_cli_image_to_jpeg_spec.rb
index 5651b5d3..561fa683 100644
--- a/spec/derivative_transformers/vips_cli_image_to_jpeg_spec.rb
+++ b/spec/derivative_transformers/vips_cli_image_to_jpeg_spec.rb
@@ -26,6 +26,16 @@
 
         output.close!
       end
+
+      describe "with add_metadata" do
+        it "adds metadata" do
+          add_metadata = {}
+
+          Kithe::VipsCliImageToJpeg.new(thumbnail_mode: true, max_width: width).call(input_file, add_metadata: add_metadata)
+          expect(add_metadata[:vips_version]).to match /\d+\.\d+\.\d+/
+          expect(add_metadata[:vips_command]).to match /vipsthumbnail .*\.jpg\[Q=85,interlace,optimize_coding,keep=none\]/
+        end
+      end
     end
   end
 
@@ -53,6 +63,17 @@
 
         output.close!
       end
+
+      describe "with add_metadata" do
+        it "adds metadata" do
+          add_metadata = {}
+
+          Kithe::VipsCliImageToJpeg.new(thumbnail_mode: false, max_width: width).call(input_file, add_metadata: add_metadata)
+          expect(add_metadata[:vips_version]).to match /\d+\.\d+\.\d+/
+          expect(add_metadata[:vips_command]).to match /vipsthumbnail .*\.jpg\[Q=85,interlace,optimize_coding\]/
+        end
+      end
+
     end
   end
 end
diff --git a/spec/models/kithe/asset/asset_derivatives_spec.rb b/spec/models/kithe/asset/asset_derivatives_spec.rb
index 086a8b58..da151f27 100644
--- a/spec/models/kithe/asset/asset_derivatives_spec.rb
+++ b/spec/models/kithe/asset/asset_derivatives_spec.rb
@@ -171,5 +171,34 @@
         end
       end
     end
+
+    describe "with specified addiitonal metadata" do
+      temporary_class("CustomUploader2") do
+        call_fakeio = method(:fakeio) # weird closure issue
+        deriv_path = derivative_file_path
+        Class.new(Kithe::AssetUploader) do
+          self::Attacher.define_derivative(:fixed_with_metadata) do |io, add_metadata:|
+            add_metadata[:added_metadata] = "set value"
+            call_fakeio.(File.binread(deriv_path))
+          end
+        end
+      end
+
+      temporary_class("CustomAsset2") do
+        Class.new(Kithe::Asset) do
+          set_shrine_uploader(CustomUploader2)
+        end
+      end
+
+      it "automatically sets up derivative properly" do
+        asset = CustomAsset2.create!(title: "test", file: File.open(original_file_path))
+        # happened in BG job, so have to reload to see it.
+        asset.reload
+
+        derivative = asset.file_derivatives[:fixed_with_metadata]
+        expect(derivative).to be_present
+        expect(derivative.metadata["added_metadata"]).to eq "set value"
+      end
+    end
   end
 end