diff --git a/config.go b/config.go
index 51036cb..e01e6e6 100644
--- a/config.go
+++ b/config.go
@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"log"
+	"net/url"
 	"os"
 
 	"slices"
@@ -12,7 +13,8 @@ import (
 )
 
 type Config struct {
-	Data Data
+	Data   Data
+	Output url.URL
 }
 
 type Data struct {
@@ -35,6 +37,9 @@ func newConfig() (Config, error) {
 	}
 	result.Data.Weight.Floor = 12
 	result.Data.Weight.Range = 20
+	result.Output = url.URL{Scheme: "file", Path: "/tmp/f"}
+	result.Data.Title = os.Getenv("TITLE")
+	result.Data.Subtitle = os.Getenv("SUBTITLE")
 
 	if js := os.Getenv("POINTS_JSON"); js == "" {
 	} else if err := json.Unmarshal([]byte(js), &result.Data.Points); err != nil {
@@ -74,8 +79,12 @@ func newConfig() (Config, error) {
 		return result, fmt.Errorf("found negative weight floor %d", result.Data.Weight.Floor)
 	}
 
-	result.Data.Title = os.Getenv("TITLE")
-	result.Data.Subtitle = os.Getenv("SUBTITLE")
+	if s := os.Getenv("OUTPUT"); s == "" {
+	} else if u, err := url.Parse(s); err != nil {
+		return result, fmt.Errorf("failed to parse $OUTPUT (%s): %w", s, err)
+	} else {
+		result.Output = *u
+	}
 
 	return result, nil
 }
diff --git a/main.go b/main.go
index 11e5b55..8c4e097 100644
--- a/main.go
+++ b/main.go
@@ -1,7 +1,9 @@
 package main
 
 import (
+	"bytes"
 	"context"
+	"fmt"
 	"log"
 	"os"
 	"os/signal"
@@ -50,12 +52,15 @@ func run(ctx context.Context) error {
 	}))
 	scatter.SetXAxis(xs).
 		AddSeries(y, ys)
-	f, _ := os.Create("/tmp/f")
-	defer f.Close()
-	if err := scatter.Render(f); err != nil {
+
+	buff := bytes.NewBuffer(nil)
+	if err := scatter.Render(buff); err != nil {
 		return err
 	}
 
-	log.Println("firefox /tmp/f")
-	return nil
+	switch config.Output.Scheme {
+	case "file":
+		return os.WriteFile(config.Output.Path, buff.Bytes(), os.ModePerm)
+	}
+	return fmt.Errorf("not impl output scheme: %s", config.Output.Scheme)
 }