diff --git a/main.go b/main.go
index 839600e..90a0445 100644
--- a/main.go
+++ b/main.go
@@ -20,6 +20,7 @@ import (
 	"bytes"
 	"flag"
 	"fmt"
+	"html/template"
 	"io/ioutil"
 	"log"
 	"os"
@@ -44,9 +45,10 @@ Flags:
 `
 
 var (
-	holder  = flag.String("c", "Google LLC", "copyright holder")
-	license = flag.String("l", "apache", "license type: apache, bsd, mit")
-	year    = flag.Int("y", time.Now().Year(), "year")
+	holder   = flag.String("c", "Google LLC", "copyright holder")
+	license  = flag.String("l", "apache", "license type: apache, bsd, mit")
+	licensef = flag.String("f", "", "license file")
+	year     = flag.Int("y", time.Now().Year(), "year")
 )
 
 func main() {
@@ -65,6 +67,26 @@ func main() {
 		Holder: *holder,
 	}
 
+	var t *template.Template
+	if *licensef != "" {
+		d, err := ioutil.ReadFile(*licensef)
+		if err != nil {
+			log.Printf("license file: %v", err)
+			os.Exit(1)
+		}
+		t, err = template.New("").Parse(string(d))
+		if err != nil {
+			log.Printf("license file: %v", err)
+			os.Exit(1)
+		}
+	} else {
+		t = licenseTemplate[*license]
+		if t == nil {
+			log.Printf("unknown license: %s", *license)
+			os.Exit(1)
+		}
+	}
+
 	// process at most 1000 files in parallel
 	ch := make(chan *file, 1000)
 	done := make(chan struct{})
@@ -73,7 +95,7 @@ func main() {
 		for f := range ch {
 			wg.Add(1)
 			go func(f *file) {
-				err := addLicense(f.path, f.mode, *license, data)
+				err := addLicense(f.path, f.mode, t, data)
 				if err != nil {
 					log.Printf("%s: %v", f.path, err)
 				}
@@ -110,30 +132,30 @@ func walk(ch chan<- *file, start string) {
 	})
 }
 
-func addLicense(path string, fmode os.FileMode, typ string, data *copyrightData) error {
+func addLicense(path string, fmode os.FileMode, tmpl *template.Template, data *copyrightData) error {
 	var lic []byte
 	var err error
 	switch filepath.Ext(path) {
 	default:
 		return nil
 	case ".c", ".h":
-		lic, err = prefix(typ, data, "/*", " * ", " */")
+		lic, err = prefix(tmpl, data, "/*", " * ", " */")
 	case ".js", ".jsx", ".tsx", ".css", ".tf":
-		lic, err = prefix(typ, data, "/**", " * ", " */")
+		lic, err = prefix(tmpl, data, "/**", " * ", " */")
 	case ".cc", ".cpp", ".cs", ".go", ".hh", ".hpp", ".java", ".m", ".mm", ".proto", ".rs", ".scala", ".swift", ".dart":
-		lic, err = prefix(typ, data, "", "// ", "")
+		lic, err = prefix(tmpl, data, "", "// ", "")
 	case ".py", ".sh", ".yaml", ".yml":
-		lic, err = prefix(typ, data, "", "# ", "")
+		lic, err = prefix(tmpl, data, "", "# ", "")
 	case ".el", ".lisp":
-		lic, err = prefix(typ, data, "", ";; ", "")
+		lic, err = prefix(tmpl, data, "", ";; ", "")
 	case ".erl":
-		lic, err = prefix(typ, data, "", "% ", "")
+		lic, err = prefix(tmpl, data, "", "% ", "")
 	case ".hs", ".sql":
-		lic, err = prefix(typ, data, "", "-- ", "")
+		lic, err = prefix(tmpl, data, "", "-- ", "")
 	case ".html", ".xml":
-		lic, err = prefix(typ, data, "<!--", " ", "-->")
+		lic, err = prefix(tmpl, data, "<!--", " ", "-->")
 	case ".php":
-		lic, err = prefix(typ, data, "<?php", "// ", "?>")
+		lic, err = prefix(tmpl, data, "<?php", "// ", "?>")
 	}
 	if err != nil || lic == nil {
 		return err
diff --git a/tmpl.go b/tmpl.go
index 6119c1c..6ac2fbc 100644
--- a/tmpl.go
+++ b/tmpl.go
@@ -36,14 +36,9 @@ type copyrightData struct {
 	Holder string
 }
 
-// prefix will execute a license template l with data d
+// prefix will execute a license template t with data d
 // and prefix the result with top, middle and bottom.
-func prefix(l string, d *copyrightData, top, mid, bot string) ([]byte, error) {
-	t := licenseTemplate[l]
-	if t == nil {
-		return nil, fmt.Errorf("unknown license: %s", l)
-	}
-
+func prefix(t *template.Template, d *copyrightData, top, mid, bot string) ([]byte, error) {
 	var buf bytes.Buffer
 	if err := t.Execute(&buf, d); err != nil {
 		return nil, err