diff --git a/cmd/browsers.go b/cmd/browsers.go
index f3de63c..3539dba 100644
--- a/cmd/browsers.go
+++ b/cmd/browsers.go
@@ -1940,7 +1940,7 @@ func (b BrowsersCmd) ExtensionsUpload(ctx context.Context, in BrowsersExtensions
 		tempZipPath := filepath.Join(os.TempDir(), fmt.Sprintf("kernel-ext-%s.zip", extName))
 
 		pterm.Info.Printf("Zipping %s as %s...\n", extPath, extName)
-		if err := util.ZipDirectory(extPath, tempZipPath); err != nil {
+		if err := util.ZipDirectory(extPath, tempZipPath, nil); err != nil {
 			pterm.Error.Printf("Failed to zip %s: %v\n", extPath, err)
 			return nil
 		}
diff --git a/cmd/deploy.go b/cmd/deploy.go
index 72301b8..e826eb0 100644
--- a/cmd/deploy.go
+++ b/cmd/deploy.go
@@ -236,7 +236,7 @@ func runDeploy(cmd *cobra.Command, args []string) (err error) {
 	}
 	tmpFile := filepath.Join(os.TempDir(), fmt.Sprintf("kernel_%d.zip", time.Now().UnixNano()))
 	logger.Debug("compressing files", logger.Args("sourceDir", sourceDir, "tmpFile", tmpFile))
-	if err := util.ZipDirectory(sourceDir, tmpFile); err != nil {
+	if err := util.ZipDirectory(sourceDir, tmpFile, nil); err != nil {
 		if spinner != nil {
 			spinner.Fail("Failed to compress files")
 		}
diff --git a/cmd/extensions.go b/cmd/extensions.go
index 9b063b5..ca7e211 100644
--- a/cmd/extensions.go
+++ b/cmd/extensions.go
@@ -18,6 +18,29 @@ import (
 	"github.com/spf13/cobra"
 )
 
+const (
+	MaxExtensionSizeBytes = 50 * 1024 * 1024 // 50MB
+)
+
+// defaultExtensionExclusions contains patterns for files that are not needed
+// when zipping Chrome extensions
+var defaultExtensionExclusions = util.ZipOptions{
+	ExcludeDirectories: []string{
+		"node_modules",
+		".git",
+		"__tests__",
+		"coverage",
+	},
+	ExcludeFilenamePatterns: []string{
+		"*.test.js",
+		"*.test.ts",
+		"*.spec.js",
+		"*.spec.ts",
+		"*.log",
+		"*.swp",
+	},
+}
+
 // ExtensionsService defines the subset of the Kernel SDK extension client that we use.
 type ExtensionsService interface {
 	List(ctx context.Context, opts ...option.RequestOption) (res *[]kernel.ExtensionListResponse, err error)
@@ -294,26 +317,57 @@ func (e ExtensionsCmd) Upload(ctx context.Context, in ExtensionsUploadInput) err
 		return fmt.Errorf("directory %s does not exist", absDir)
 	}
 
+	// Pre-flight size check
+	if in.Output != "json" {
+		pterm.Info.Println("Analyzing extension directory...")
+	}
+
 	tmpFile := filepath.Join(os.TempDir(), fmt.Sprintf("kernel_ext_%d.zip", time.Now().UnixNano()))
+
 	if in.Output != "json" {
 		pterm.Info.Println("Zipping extension directory...")
 	}
-	if err := util.ZipDirectory(absDir, tmpFile); err != nil {
+
+	if err := util.ZipDirectory(absDir, tmpFile, &defaultExtensionExclusions); err != nil {
 		pterm.Error.Println("Failed to zip directory")
 		return err
 	}
 	defer os.Remove(tmpFile)
 
+	fileInfo, err := os.Stat(tmpFile)
+	if err != nil {
+		return fmt.Errorf("failed to stat zip: %w", err)
+	}
+
+	if in.Output != "json" {
+		pterm.Success.Printf("Created bundle: %s\n", util.FormatBytes(fileInfo.Size()))
+	}
+
+	if fileInfo.Size() > MaxExtensionSizeBytes {
+		pterm.Error.Printf("Extension bundle is too large: %s (max: 50MB)\n",
+			util.FormatBytes(fileInfo.Size()))
+		pterm.Info.Println("\nSuggestions to reduce size:")
+		pterm.Info.Println("  1. Ensure you're building the extension for production")
+		pterm.Info.Println("  2. Remove unnecessary assets (large images, videos)")
+		pterm.Info.Println("  3. Check manifest.json references only needed files")
+		return fmt.Errorf("bundle exceeds maximum size")
+	}
+
 	f, err := os.Open(tmpFile)
 	if err != nil {
 		return fmt.Errorf("failed to open temp zip: %w", err)
 	}
 	defer f.Close()
 
+	if in.Output != "json" {
+		pterm.Info.Println("Uploading extension...")
+	}
+
 	params := kernel.ExtensionUploadParams{File: f}
 	if in.Name != "" {
 		params.Name = kernel.Opt(in.Name)
 	}
+
 	item, err := e.extensions.Upload(ctx, params)
 	if err != nil {
 		return util.CleanedUpSdkError{Err: err}
diff --git a/pkg/util/format.go b/pkg/util/format.go
index 7f64590..6682655 100644
--- a/pkg/util/format.go
+++ b/pkg/util/format.go
@@ -1,6 +1,9 @@
 package util
 
-import "strings"
+import (
+	"fmt"
+	"strings"
+)
 
 // OrDash returns the string if non-empty, otherwise returns "-".
 func OrDash(s string) string {
@@ -29,3 +32,17 @@ func JoinOrDash(items ...string) string {
 	}
 	return strings.Join(items, ", ")
 }
+
+// FormatBytes formats bytes in a human-readable format
+func FormatBytes(bytes int64) string {
+	const unit = 1024
+	if bytes < unit {
+		return fmt.Sprintf("%d B", bytes)
+	}
+	div, exp := int64(unit), 0
+	for n := bytes / unit; n >= unit; n /= unit {
+		div *= unit
+		exp++
+	}
+	return fmt.Sprintf("%.1f %cB", float64(bytes)/float64(div), "KMGTPE"[exp])
+}
diff --git a/pkg/util/zip.go b/pkg/util/zip.go
index 468721d..111bca0 100644
--- a/pkg/util/zip.go
+++ b/pkg/util/zip.go
@@ -11,8 +11,16 @@ import (
 	"github.com/boyter/gocodewalker"
 )
 
+// ZipOptions which directories and files to exclude from the zip
+type ZipOptions struct {
+	// ExcludeDirectories: exact directory names to exclude (case-sensitive)
+	ExcludeDirectories []string
+	// ExcludeFilenamePatterns: glob patterns for filename exclusion (e.g., "*.test.js")
+	ExcludeFilenamePatterns []string
+}
+
 // ZipDirectory compresses the given source directory into the destination file path.
-func ZipDirectory(srcDir, destZip string) error {
+func ZipDirectory(srcDir, destZip string, opts *ZipOptions) error {
 	zipFile, err := os.Create(destZip)
 	if err != nil {
 		return err
@@ -28,9 +36,16 @@ func ZipDirectory(srcDir, destZip string) error {
 	// Include hidden files (to match previous behaviour) but still respect .gitignore rules
 	walker.IncludeHidden = true
 
-	// Start walking in a separate goroutine so we can process files as they arrive
+	// Apply directory exclusions to walker
+	if opts != nil {
+		walker.ExcludeDirectory = append(walker.ExcludeDirectory, opts.ExcludeDirectories...)
+	}
+
+	defer walker.Terminate()
+
+	errChan := make(chan error, 1)
 	go func() {
-		_ = walker.Start()
+		errChan <- walker.Start()
 	}()
 
 	// Track directories we've already added to the zip archive so we don't duplicate entries
@@ -44,6 +59,22 @@ func ZipDirectory(srcDir, destZip string) error {
 		}
 		relPath = filepath.ToSlash(relPath)
 
+		// Check against pattern-based exclusions if provided
+		if opts != nil && len(opts.ExcludeFilenamePatterns) > 0 {
+			filename := filepath.Base(f.Location)
+			shouldExclude := false
+			for _, pattern := range opts.ExcludeFilenamePatterns {
+				matched, err := filepath.Match(pattern, filename)
+				if err == nil && matched {
+					shouldExclude = true
+					break
+				}
+			}
+			if shouldExclude {
+				continue
+			}
+		}
+
 		// Ensure parent directories exist in the archive
 		if dir := filepath.Dir(relPath); dir != "." && dir != "" {
 			// Walk up the directory tree ensuring each level exists
@@ -115,6 +146,10 @@ func ZipDirectory(srcDir, destZip string) error {
 		}
 	}
 
+	if err := <-errChan; err != nil {
+		return fmt.Errorf("directory walk failed: %w", err)
+	}
+
 	return nil
 }
 
diff --git a/pkg/util/zip_test.go b/pkg/util/zip_test.go
new file mode 100644
index 0000000..6fbeb37
--- /dev/null
+++ b/pkg/util/zip_test.go
@@ -0,0 +1,178 @@
+package util
+
+import (
+	"archive/zip"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestZipDirectory(t *testing.T) {
+	tmpDir, err := os.MkdirTemp("", "zip-test-*")
+	if err != nil {
+		t.Fatalf("Failed to create temp dir: %v", err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	files := map[string]string{
+		"manifest.json":           `{"name": "test", "version": "1.0"}`,
+		"background.js":           "console.log('background');",
+		"content.js":              "console.log('content');",
+		"icons/icon.png":          "fake-png-data",
+		"node_modules/dep/foo.js": "should be excluded",
+		"test.test.js":            "should be excluded",
+	}
+
+	for path, content := range files {
+		fullPath := filepath.Join(tmpDir, path)
+		dir := filepath.Dir(fullPath)
+		if err := os.MkdirAll(dir, 0755); err != nil {
+			t.Fatalf("Failed to create directory %s: %v", dir, err)
+		}
+		if err := os.WriteFile(fullPath, []byte(content), 0644); err != nil {
+			t.Fatalf("Failed to write file %s: %v", fullPath, err)
+		}
+	}
+
+	tmpZip, err := os.CreateTemp("", "test-zip-*.zip")
+	if err != nil {
+		t.Fatalf("Failed to create temp zip: %v", err)
+	}
+	tmpZip.Close()
+	defer os.Remove(tmpZip.Name())
+
+	// Test with exclusions
+	t.Run("with exclusions", func(t *testing.T) {
+		opts := &ZipOptions{
+			ExcludeDirectories:      []string{"node_modules"},
+			ExcludeFilenamePatterns: []string{"*.test.js"},
+		}
+		if err := ZipDirectory(tmpDir, tmpZip.Name(), opts); err != nil {
+			t.Fatalf("ZipDirectory failed: %v", err)
+		}
+
+		// Verify the zip contents
+		r, err := zip.OpenReader(tmpZip.Name())
+		if err != nil {
+			t.Fatalf("Failed to open zip: %v", err)
+		}
+		defer r.Close()
+
+		expectedFiles := map[string]bool{
+			"manifest.json":  false,
+			"background.js":  false,
+			"content.js":     false,
+			"icons/":         false,
+			"icons/icon.png": false,
+		}
+
+		for _, f := range r.File {
+			if f.FileInfo().IsDir() {
+				expectedFiles[f.Name] = true
+			} else {
+				if _, ok := expectedFiles[f.Name]; ok {
+					expectedFiles[f.Name] = true
+				} else {
+					t.Errorf("Unexpected file found in zip: %s", f.Name)
+				}
+			}
+		}
+
+		for name, found := range expectedFiles {
+			if !found && name != "icons/" {
+				t.Errorf("Expected file not found in zip: %s", name)
+			}
+		}
+	})
+
+	// Test without exclusions (nil opts)
+	t.Run("without exclusions", func(t *testing.T) {
+		tmpZip2, err := os.CreateTemp("", "test-zip-no-exclude-*.zip")
+		if err != nil {
+			t.Fatalf("Failed to create temp zip: %v", err)
+		}
+		tmpZip2.Close()
+		defer os.Remove(tmpZip2.Name())
+
+		if err := ZipDirectory(tmpDir, tmpZip2.Name(), nil); err != nil {
+			t.Fatalf("ZipDirectory failed: %v", err)
+		}
+
+		// Verify all files are included (no exclusions)
+		r, err := zip.OpenReader(tmpZip2.Name())
+		if err != nil {
+			t.Fatalf("Failed to open zip: %v", err)
+		}
+		defer r.Close()
+
+		fileCount := 0
+		for _, f := range r.File {
+			if !f.FileInfo().IsDir() {
+				fileCount++
+			}
+		}
+		if fileCount <= 4 {
+			t.Errorf("Expected more than 4 files when exclusions are disabled, got %d", fileCount)
+		}
+	})
+}
+
+func TestUnzip(t *testing.T) {
+	tmpZip, err := os.CreateTemp("", "test-unzip-*.zip")
+	if err != nil {
+		t.Fatalf("Failed to create temp zip: %v", err)
+	}
+	tmpZip.Close()
+	defer os.Remove(tmpZip.Name())
+
+	zw, err := os.Create(tmpZip.Name())
+	if err != nil {
+		t.Fatalf("Failed to open zip for writing: %v", err)
+	}
+	zipWriter := zip.NewWriter(zw)
+
+	testFiles := map[string]string{
+		"file1.txt":        "content of file 1",
+		"subdir/file2.txt": "content of file 2",
+	}
+
+	if _, err := zipWriter.Create("subdir/"); err != nil {
+		t.Fatalf("Failed to create dir entry: %v", err)
+	}
+
+	for name, content := range testFiles {
+		w, err := zipWriter.Create(name)
+		if err != nil {
+			t.Fatalf("Failed to create zip entry %s: %v", name, err)
+		}
+		if _, err := w.Write([]byte(content)); err != nil {
+			t.Fatalf("Failed to write zip entry %s: %v", name, err)
+		}
+	}
+	zipWriter.Close()
+	zw.Close()
+
+	// Unzip to temp directory
+	destDir, err := os.MkdirTemp("", "test-unzip-dest-*")
+	if err != nil {
+		t.Fatalf("Failed to create dest dir: %v", err)
+	}
+	defer os.RemoveAll(destDir)
+
+	if err := Unzip(tmpZip.Name(), destDir); err != nil {
+		t.Fatalf("Unzip failed: %v", err)
+	}
+
+	// Verify extracted files
+	for name, expectedContent := range testFiles {
+		path := filepath.Join(destDir, name)
+		content, err := os.ReadFile(path)
+		if err != nil {
+			t.Errorf("Failed to read extracted file %s: %v", name, err)
+			continue
+		}
+		if string(content) != expectedContent {
+			t.Errorf("File %s: expected %q, got %q", name, expectedContent, string(content))
+		}
+	}
+}