diff --git a/cmd/root.go b/cmd/root.go
index 1cf2d18..7a6e4a7 100644
--- a/cmd/root.go
+++ b/cmd/root.go
@@ -6,6 +6,7 @@ import (
 	"github.com/remove-bg/go/processor"
 	"github.com/spf13/cobra"
 	"os"
+	"strings"
 )
 
 const defaultLargeBatchSize = 50
@@ -50,7 +51,7 @@ var RootCmd = &cobra.Command{
 				Channels:        imageChannels,
 				BgColor:         bgColor,
 				BgImageFile:     bgImageFile,
-				Format:          imageFormat,
+				Format:          strings.ToLower(imageFormat),
 				ExtraApiOptions: extraApiOptions,
 			},
 		}
diff --git a/processor/processor.go b/processor/processor.go
index b81f76b..f3a2b76 100644
--- a/processor/processor.go
+++ b/processor/processor.go
@@ -64,6 +64,8 @@ func (p Processor) Process(rawInputPaths []string, settings Settings) {
 		return
 	}
 
+	settings.ImageSettings.upgradePngToZipFormat()
+
 	totalImages := len(inputPaths)
 
 	for index, inputPath := range inputPaths {
@@ -85,6 +87,17 @@ func (p Processor) Process(rawInputPaths []string, settings Settings) {
 	}
 }
 
+const FormatPng = "png"
+const FormatZip = "zip"
+const MimeZip = "application/zip"
+
+func (is *ImageSettings) upgradePngToZipFormat() {
+	// Save network bandwidth by requesting ZIP format (output will still be a PNG)
+	if is.Format == FormatPng {
+		is.Format = FormatZip
+	}
+}
+
 func (p Processor) processFile(inputPath string, outputPath string, imageSettings ImageSettings) error {
 	params := imageSettingsToParams(imageSettings)
 	processedBytes, contentType, err := p.Client.RemoveFromFile(inputPath, p.APIKey, params)
@@ -92,7 +105,7 @@ func (p Processor) processFile(inputPath string, outputPath string, imageSetting
 		return err
 	}
 
-	if strings.Contains(contentType, "application/zip") {
+	if strings.Contains(contentType, MimeZip) {
 		return p.processCompositeFile(outputPath, processedBytes)
 	} else {
 		return p.Storage.Write(outputPath, processedBytes)
diff --git a/processor/processor_test.go b/processor/processor_test.go
index b2b71a8..482972b 100644
--- a/processor/processor_test.go
+++ b/processor/processor_test.go
@@ -11,8 +11,7 @@ import (
 	"github.com/remove-bg/go/storage/storagefakes"
 )
 
-const zipMime = "application/zip"
-const pngMime = "image/png"
+const mimePng = "image/png"
 
 var _ = Describe("Processor", func() {
 	var (
@@ -67,8 +66,8 @@ var _ = Describe("Processor", func() {
 	})
 
 	It("coordinates the HTTP request and writing the result", func() {
-		fakeClient.RemoveFromFileReturnsOnCall(0, []byte("Processed1"), pngMime, nil)
-		fakeClient.RemoveFromFileReturnsOnCall(1, []byte("Processed2"), pngMime, nil)
+		fakeClient.RemoveFromFileReturnsOnCall(0, []byte("Processed1"), mimePng, nil)
+		fakeClient.RemoveFromFileReturnsOnCall(1, []byte("Processed2"), mimePng, nil)
 
 		inputPaths := []string{"dir/image1.jpg", "dir/image2.jpg"}
 
@@ -88,15 +87,49 @@ var _ = Describe("Processor", func() {
 		Expect(writerArg2).To(Equal([]byte("Processed1")))
 	})
 
-	Context("zip format result", func() {
+	Context("zip format requested", func() {
 		It("delegates to the compositor", func() {
 			fakeCompositor.ProcessReturns(nil)
-			fakeClient.RemoveFromFileReturnsOnCall(0, []byte("Zip1"), zipMime, nil)
-			fakeClient.RemoveFromFileReturnsOnCall(1, []byte("Zip2"), zipMime, nil)
+			fakeClient.RemoveFromFileReturnsOnCall(0, []byte("Zip1"), processor.MimeZip, nil)
+			fakeClient.RemoveFromFileReturnsOnCall(1, []byte("Zip2"), processor.MimeZip, nil)
 
 			inputPaths := []string{"dir/image1.jpg", "dir/image2.jpg"}
 			testSettings.OutputDirectory = "out-dir"
-			testSettings.ImageSettings.Format = "zip"
+			testSettings.ImageSettings.Format = processor.FormatZip
+
+			subject.Process(inputPaths, testSettings)
+
+			Expect(fakeCompositor.ProcessCallCount()).To(Equal(2))
+
+			zipFileName, outputPath := fakeCompositor.ProcessArgsForCall(0)
+			Expect(zipFileName).To(ContainSubstring(".zip"))
+			Expect(outputPath).To(Equal("out-dir/image1.png"))
+		})
+	})
+
+	Context("png format requested", func() {
+		BeforeEach(func() {
+			fakeCompositor.ProcessReturns(nil)
+			fakeClient.RemoveFromFileReturnsOnCall(0, []byte("Zip1"), processor.MimeZip, nil)
+			fakeClient.RemoveFromFileReturnsOnCall(1, []byte("Zip2"), processor.MimeZip, nil)
+		})
+
+		It("upgrades the format to zip behind the scenes", func() {
+			inputPaths := []string{"dir/image1.jpg", "dir/image2.jpg"}
+			testSettings.OutputDirectory = "out-dir"
+			testSettings.ImageSettings.Format = processor.FormatPng
+
+			subject.Process(inputPaths, testSettings)
+
+			Expect(fakeClient.RemoveFromFileCallCount()).To(Equal(2))
+			_, _, params := fakeClient.RemoveFromFileArgsForCall(0)
+			Expect(params["format"]).To(Equal(processor.FormatZip))
+		})
+
+		It("delegates to the compositor", func() {
+			inputPaths := []string{"dir/image1.jpg", "dir/image2.jpg"}
+			testSettings.OutputDirectory = "out-dir"
+			testSettings.ImageSettings.Format = processor.FormatPng
 
 			subject.Process(inputPaths, testSettings)
 
@@ -110,7 +143,7 @@ var _ = Describe("Processor", func() {
 
 	Describe("image options", func() {
 		It("passes non-empty image options to the client", func() {
-			fakeClient.RemoveFromFileReturnsOnCall(0, []byte("Processed1"), pngMime, nil)
+			fakeClient.RemoveFromFileReturnsOnCall(0, []byte("Processed1"), mimePng, nil)
 			inputPaths := []string{"dir/image1.jpg"}
 
 			testSettings.ImageSettings = processor.ImageSettings{
@@ -122,15 +155,6 @@ var _ = Describe("Processor", func() {
 				Format:      "format-value",
 			}
 
-			testSettings.ImageSettings = processor.ImageSettings{
-				Size:        "size-value",
-				Type:        "type-value",
-				Channels:    "channels-value",
-				BgColor:     "bg-color-value",
-				BgImageFile: "bg-image-file-value",
-				Format:      "format-value",
-			}
-
 			subject.Process(inputPaths, testSettings)
 
 			Expect(fakeClient.RemoveFromFileCallCount()).To(Equal(1))
@@ -145,7 +169,7 @@ var _ = Describe("Processor", func() {
 		})
 
 		It("parses any extra API options into params", func() {
-			fakeClient.RemoveFromFileReturnsOnCall(0, []byte("Processed1"), pngMime, nil)
+			fakeClient.RemoveFromFileReturnsOnCall(0, []byte("Processed1"), mimePng, nil)
 			inputPaths := []string{"dir/image1.jpg"}
 
 			testSettings.ImageSettings = processor.ImageSettings{
@@ -167,7 +191,7 @@ var _ = Describe("Processor", func() {
 	Context("client error", func() {
 		It("keeps processing images", func() {
 			fakeClient.RemoveFromFileReturnsOnCall(0, nil, "", errors.New("boom"))
-			fakeClient.RemoveFromFileReturnsOnCall(1, []byte("Processed2"), pngMime, nil)
+			fakeClient.RemoveFromFileReturnsOnCall(1, []byte("Processed2"), mimePng, nil)
 			inputPaths := []string{"dir/image1.jpg", "dir/image2.jpg"}
 
 			subject.Process(inputPaths, testSettings)
@@ -184,7 +208,7 @@ var _ = Describe("Processor", func() {
 		It("passes the error details to the notifier", func() {
 			err := errors.New("boom")
 			fakeClient.RemoveFromFileReturnsOnCall(0, nil, "", err)
-			fakeClient.RemoveFromFileReturnsOnCall(1, []byte("Processed2"), pngMime, nil)
+			fakeClient.RemoveFromFileReturnsOnCall(1, []byte("Processed2"), mimePng, nil)
 			inputPaths := []string{"dir/image1.jpg", "dir/image2.jpg"}
 
 			subject.Process(inputPaths, testSettings)
@@ -202,8 +226,8 @@ var _ = Describe("Processor", func() {
 
 	Context("writer error", func() {
 		It("keeps processing images", func() {
-			fakeClient.RemoveFromFileReturnsOnCall(0, []byte("Processed1"), pngMime, nil)
-			fakeClient.RemoveFromFileReturnsOnCall(1, []byte("Processed2"), pngMime, nil)
+			fakeClient.RemoveFromFileReturnsOnCall(0, []byte("Processed1"), mimePng, nil)
+			fakeClient.RemoveFromFileReturnsOnCall(1, []byte("Processed2"), mimePng, nil)
 			fakeStorage.WriteReturnsOnCall(0, errors.New("boom"))
 			inputPaths := []string{"dir/image1.jpg", "dir/image2.jpg"}
 
@@ -216,8 +240,8 @@ var _ = Describe("Processor", func() {
 
 		It("passes the error details to the notifier", func() {
 			err := errors.New("boom")
-			fakeClient.RemoveFromFileReturnsOnCall(0, []byte("Processed1"), pngMime, nil)
-			fakeClient.RemoveFromFileReturnsOnCall(1, []byte("Processed2"), pngMime, nil)
+			fakeClient.RemoveFromFileReturnsOnCall(0, []byte("Processed1"), mimePng, nil)
+			fakeClient.RemoveFromFileReturnsOnCall(1, []byte("Processed2"), mimePng, nil)
 			fakeStorage.WriteReturnsOnCall(0, err)
 			inputPaths := []string{"dir/image1.jpg", "dir/image2.jpg"}