diff --git a/pmtiles/write.go b/pmtiles/write.go
new file mode 100644
index 0000000..af9935a
--- /dev/null
+++ b/pmtiles/write.go
@@ -0,0 +1,45 @@
+package pmtiles
+
+import (
+	"fmt"
+	"log"
+	"os"
+)
+
+func Write(logger *log.Logger, inputArchive string, newHeaderJsonFile string, newMetadataFile string) error {
+
+	if newMetadataFile == "" {
+		if newHeaderJsonFile == "" {
+			return fmt.Errorf("No data to write.")
+		}
+
+		// we can write the header in-place without writing the whole file.
+	}
+
+ 	file, err := os.OpenFile(inputArchive, os.O_RDWR, 0666)
+
+	buf := make([]byte, 127)
+	_, err = file.Read(buf)
+	if err != nil {
+		return err
+	}
+	originalHeader, _ := deserializeHeader(buf)
+
+	// modify the header
+
+	buf = serializeHeader(originalHeader)
+	_, err = file.WriteAt(buf, 0)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+
+// write metadata:
+// always writes in this order:
+// copy the header
+// copy the root directory
+// write the new the metadata
+// copy the leaf directories
+// copy the tile data
diff --git a/pmtiles/write_test.go b/pmtiles/write_test.go
new file mode 100644
index 0000000..adf2fe3
--- /dev/null
+++ b/pmtiles/write_test.go
@@ -0,0 +1,29 @@
+package pmtiles
+
+import (
+	// "log"
+	"os"
+	"io"
+	"io/ioutil"
+	"path/filepath"
+	"testing"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestWriteHeader(t *testing.T) {
+	// logger := log.New(os.Stdout, "", log.Ldate|log.Ltime|log.Lshortfile)
+
+	tempDir, _ := ioutil.TempDir("", "testing")
+	defer os.RemoveAll(tempDir)
+	src, _ := os.Open("fixtures/test_fixture_1.pmtiles")
+	defer src.Close()
+	dest, _ := os.Create(filepath.Join(tempDir, "test.pmtiles"))
+	defer dest.Close()
+	_, _ = io.Copy(dest, src)
+
+	assert.Nil(t, nil)
+
+	// var input map[string]interface{}
+	// json.Unmarshal(b.Bytes(), &input)
+	// assert.Equal(t, "tippecanoe v2.5.0", input["generator"])
+}