diff --git a/app/collector.go b/app/collector.go
index 51cce7092..659fe242a 100644
--- a/app/collector.go
+++ b/app/collector.go
@@ -1,9 +1,7 @@
 package app
 
 import (
-	"compress/gzip"
 	"fmt"
-	"io/ioutil"
 	"os"
 	"path/filepath"
 	"strconv"
@@ -11,7 +9,6 @@ import (
 	"sync"
 	"time"
 
-	"github.com/ugorji/go/codec"
 	"golang.org/x/net/context"
 
 	"github.com/weaveworks/common/mtime"
@@ -234,7 +231,7 @@ func NewFileCollector(path string, window time.Duration) (Collector, error) {
 			}
 			timestamps = append(timestamps, t)
 
-			rpt, err := readReport(p)
+			rpt, err := report.MakeFromFile(p)
 			if err != nil {
 				return err
 			}
@@ -267,49 +264,6 @@ func timestampFromFilepath(path string) (time.Time, error) {
 	return time.Unix(0, nanosecondsSinceEpoch), nil
 }
 
-func readReport(path string) (rpt report.Report, _ error) {
-	f, err := os.Open(path)
-	if err != nil {
-		return rpt, err
-	}
-	defer f.Close()
-
-	var (
-		handle  codec.Handle
-		gzipped bool
-	)
-	fileType := filepath.Ext(path)
-	if fileType == ".gz" {
-		gzipped = true
-		fileType = filepath.Ext(strings.TrimSuffix(path, fileType))
-	}
-	switch fileType {
-	case ".json":
-		handle = &codec.JsonHandle{}
-	case ".msgpack":
-		handle = &codec.MsgpackHandle{}
-	default:
-		return rpt, fmt.Errorf("Unsupported file extension: %v", fileType)
-	}
-
-	var buf []byte
-	if gzipped {
-		r, err := gzip.NewReader(f)
-		if err != nil {
-			return rpt, err
-		}
-		buf, err = ioutil.ReadAll(r)
-	} else {
-		buf, err = ioutil.ReadAll(f)
-	}
-	if err != nil {
-		return rpt, err
-	}
-	err = rpt.ReadBytes(buf, handle)
-
-	return rpt, err
-}
-
 func replay(a Adder, timestamps []time.Time, reports []report.Report) {
 	// calculate delays between report n and n+1
 	l := len(timestamps)
diff --git a/extras/copyreport/Makefile b/extras/copyreport/Makefile
new file mode 100644
index 000000000..70334ba49
--- /dev/null
+++ b/extras/copyreport/Makefile
@@ -0,0 +1,19 @@
+.PHONY: all vet lint build test clean
+
+all: build test vet lint
+
+vet:
+	go vet ./...
+
+lint:
+	golint .
+
+build:
+	go build
+
+test:
+	go test
+
+clean:
+	go clean
+
diff --git a/extras/copyreport/main.go b/extras/copyreport/main.go
new file mode 100644
index 000000000..07e47d067
--- /dev/null
+++ b/extras/copyreport/main.go
@@ -0,0 +1,26 @@
+// Copy a report, decoding and re-encoding it.
+package main
+
+import (
+	"compress/gzip"
+	"flag"
+	"log"
+
+	"github.com/weaveworks/scope/report"
+)
+
+func main() {
+	flag.Parse()
+
+	if len(flag.Args()) != 2 {
+		log.Fatal("usage: copyreport src.(json|msgpack)[.gz] dst.(json|msgpack)[.gz]")
+	}
+
+	rpt, err := report.MakeFromFile(flag.Arg(0))
+	if err != nil {
+		log.Fatal(err)
+	}
+	if err = rpt.WriteToFile(flag.Arg(1), gzip.DefaultCompression); err != nil {
+		log.Fatal(err)
+	}
+}
diff --git a/report/marshal.go b/report/marshal.go
index f5e2e776a..36c7d2d0d 100644
--- a/report/marshal.go
+++ b/report/marshal.go
@@ -1,10 +1,15 @@
 package report
 
 import (
+	"bufio"
 	"bytes"
 	"compress/gzip"
+	"fmt"
 	"io"
 	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strings"
 
 	log "github.com/Sirupsen/logrus"
 	"github.com/ugorji/go/codec"
@@ -118,3 +123,89 @@ func MakeFromBytes(buf []byte) (*Report, error) {
 	}
 	return &rep, nil
 }
+
+// MakeFromFile construct a Report from a file, with the encoding
+// determined by the extension (".msgpack" or ".json", with an
+// optional ".gz").
+func MakeFromFile(path string) (rpt Report, _ error) {
+	f, err := os.Open(path)
+	if err != nil {
+		return rpt, err
+	}
+	defer f.Close()
+
+	handle, gzipped, err := handlerFromFileType(path)
+	if err != nil {
+		return rpt, err
+	}
+
+	var buf []byte
+	if gzipped {
+		r, err := gzip.NewReader(f)
+		if err != nil {
+			return rpt, err
+		}
+		buf, err = ioutil.ReadAll(r)
+	} else {
+		buf, err = ioutil.ReadAll(f)
+	}
+	if err != nil {
+		return rpt, err
+	}
+	err = rpt.ReadBytes(buf, handle)
+
+	return rpt, err
+}
+
+// WriteToFile writes a Report to a file. The encoding is determined
+// by the file extension (".msgpack" or ".json", with an optional
+// ".gz").
+func (rep *Report) WriteToFile(path string, compressionLevel int) error {
+	f, err := os.Create(path)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	handle, gzipped, err := handlerFromFileType(path)
+	if err != nil {
+		return err
+	}
+
+	var w io.Writer
+	bufwriter := bufio.NewWriter(f)
+	defer bufwriter.Flush()
+	w = bufwriter
+	if gzipped {
+		gzwriter, err := gzip.NewWriterLevel(w, compressionLevel)
+		if err != nil {
+			return err
+		}
+		defer gzwriter.Close()
+		w = gzwriter
+	}
+
+	if err = codec.NewEncoder(w, handle).Encode(rep); err != nil {
+		return err
+	}
+
+	return nil
+
+}
+
+func handlerFromFileType(path string) (codec.Handle, bool, error) {
+	fileType := filepath.Ext(path)
+	gzipped := false
+	if fileType == ".gz" {
+		gzipped = true
+		fileType = filepath.Ext(strings.TrimSuffix(path, fileType))
+	}
+	switch fileType {
+	case ".json":
+		return &codec.JsonHandle{}, gzipped, nil
+	case ".msgpack":
+		return &codec.MsgpackHandle{}, gzipped, nil
+	default:
+		return nil, false, fmt.Errorf("Unsupported file extension: %v", fileType)
+	}
+}