diff --git a/.gitattributes b/.gitattributes
index 0790ec8e..55209809 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -7,3 +7,4 @@
 # example, we want to allow a .txt file to contain a CRLF line ending
 *.go    text eol=lf
 *.txt   text eol=lf
+*.txtar text eol=lf
diff --git a/cmd/testscript/README.md b/cmd/testscript/README.md
index 1ebc7b55..daf9930f 100644
--- a/cmd/testscript/README.md
+++ b/cmd/testscript/README.md
@@ -37,7 +37,7 @@ script, and does not remove that directory when testscript exits.
 Examples
 ========
 
-The following example, fruit.txt, shows a simple reproduction that includes
+The following example, fruit.txtar, shows a simple reproduction that includes
 .gomodproxy supporting files:
 
     go get -m fruit.com
@@ -58,7 +58,7 @@ The following example, fruit.txt, shows a simple reproduction that includes
 
     const Name = "Apple"
 
-Running testscript -v fruit.txt we get:
+Running testscript -v fruit.txtar we get:
 
     ...
     > go get -m fruit.com
@@ -76,7 +76,7 @@ Running testscript -v fruit.txt we get:
     PASS
 
 
-The following example, goimports.txt, shows a simple reproduction involving
+The following example, goimports.txtar, shows a simple reproduction involving
 goimports:
 
     go install golang.org/x/tools/cmd/goimports
@@ -95,7 +95,7 @@ goimports:
 
     const Pi = math.Pi
 
-Running testscript -v goimports.txt we get:
+Running testscript -v goimports.txtar we get:
 
     ...
     > go install golang.org/x/tools/cmd/goimports
diff --git a/cmd/testscript/help.go b/cmd/testscript/help.go
index 4f0511af..d4808b02 100644
--- a/cmd/testscript/help.go
+++ b/cmd/testscript/help.go
@@ -48,7 +48,7 @@ script, and does not remove that directory when testscript exits.
 Examples
 ========
 
-The following example, fruit.txt, shows a simple reproduction that includes
+The following example, fruit.txtar, shows a simple reproduction that includes
 .gomodproxy supporting files:
 
     go get -m fruit.com
@@ -69,7 +69,7 @@ The following example, fruit.txt, shows a simple reproduction that includes
 
     const Name = "Apple"
 
-Running testscript -v fruit.txt we get:
+Running testscript -v fruit.txtar we get:
 
     ...
     > go get -m fruit.com
@@ -87,7 +87,7 @@ Running testscript -v fruit.txt we get:
     PASS
 
 
-The following example, goimports.txt, shows a simple reproduction involving
+The following example, goimports.txtar, shows a simple reproduction involving
 goimports:
 
     go install golang.org/x/tools/cmd/goimports
@@ -106,7 +106,7 @@ goimports:
 
     const Pi = math.Pi
 
-Running testscript -v goimports.txt we get:
+Running testscript -v goimports.txtar we get:
 
     ...
     > go install golang.org/x/tools/cmd/goimports
diff --git a/cmd/testscript/main.go b/cmd/testscript/main.go
index c38ea6a0..7908db53 100644
--- a/cmd/testscript/main.go
+++ b/cmd/testscript/main.go
@@ -196,7 +196,7 @@ func (tr *testRunner) run(runDir, filename string) error {
 		return fmt.Errorf("failed to write .gomodproxy files: %v", err)
 	}
 
-	scriptFile := filepath.Join(runDir, "script.txt")
+	scriptFile := filepath.Join(runDir, "script.txtar")
 
 	if err := ioutil.WriteFile(scriptFile, txtar.Format(&script), 0666); err != nil {
 		return fmt.Errorf("failed to write script for %v: %v", renderFilename(filename), err)
diff --git a/cmd/testscript/testdata/work.txt b/cmd/testscript/testdata/work.txt
index 42b4135a..021705cb 100644
--- a/cmd/testscript/testdata/work.txt
+++ b/cmd/testscript/testdata/work.txt
@@ -12,8 +12,8 @@ testscript -v -work file.txt dir/file.txt
 stderr '^temporary work directory: \Q'$WORK'\E[/\\]\.tmp[/\\]'
 stderr '^temporary work directory for file.txt: \Q'$WORK'\E[/\\]\.tmp[/\\]'
 stderr '^temporary work directory for dir[/\\]file.txt: \Q'$WORK'\E[/\\]\.tmp[/\\]'
-expandone $WORK/.tmp/testscript*/file.txt/script.txt
-expandone $WORK/.tmp/testscript*/file.txt1/script.txt
+expandone $WORK/.tmp/testscript*/file.txt/script.txtar
+expandone $WORK/.tmp/testscript*/file.txt1/script.txtar
 
 -- file.txt --
 >exec true
diff --git a/cmd/txtar-addmod/addmod.go b/cmd/txtar-addmod/addmod.go
index 663f1ab0..d9404650 100644
--- a/cmd/txtar-addmod/addmod.go
+++ b/cmd/txtar-addmod/addmod.go
@@ -202,7 +202,7 @@ func main1() int {
 				break
 			}
 		} else {
-			if err := ioutil.WriteFile(filepath.Join(targetDir, modDir+".txt"), data, 0666); err != nil {
+			if err := ioutil.WriteFile(filepath.Join(targetDir, modDir+".txtar"), data, 0666); err != nil {
 				log.Printf("%s: %v", arg, err)
 				exitCode = 1
 				continue
diff --git a/cmd/txtar-addmod/testdata/encode.txt b/cmd/txtar-addmod/testdata/encode.txt
index 7c1e4dab..78de04c3 100644
--- a/cmd/txtar-addmod/testdata/encode.txt
+++ b/cmd/txtar-addmod/testdata/encode.txt
@@ -2,4 +2,4 @@ mkdir $WORK/out
 txtar-addmod $WORK/out github.com/shurcooL/httpfs@v0.0.0-20171119174359-809beceb2371
 ! stdout .+
 ! stderr .+
-exists $WORK/out/github.com_shurcoo!l_httpfs_v0.0.0-20171119174359-809beceb2371.txt
+exists $WORK/out/github.com_shurcoo!l_httpfs_v0.0.0-20171119174359-809beceb2371.txtar
diff --git a/cmd/txtar-addmod/testdata/txtar-addmod-self.txt b/cmd/txtar-addmod/testdata/txtar-addmod-self.txt
index 6ed22105..fcacd91e 100644
--- a/cmd/txtar-addmod/testdata/txtar-addmod-self.txt
+++ b/cmd/txtar-addmod/testdata/txtar-addmod-self.txt
@@ -2,8 +2,8 @@ mkdir $WORK/out
 txtar-addmod $WORK/out github.com/gobin-testrepos/simple-main
 ! stdout .+
 ! stderr .+
-exists $WORK/out/github.com_gobin-testrepos_simple-main_v1.0.0.txt
-! grep foobar $WORK/out/github.com_gobin-testrepos_simple-main_v1.0.0.txt
+exists $WORK/out/github.com_gobin-testrepos_simple-main_v1.0.0.txtar
+! grep foobar $WORK/out/github.com_gobin-testrepos_simple-main_v1.0.0.txtar
 
 txtar-addmod -all $WORK/out github.com/gobin-testrepos/simple-main
-grep '-- foobar --' $WORK/out/github.com_gobin-testrepos_simple-main_v1.0.0.txt
+grep '-- foobar --' $WORK/out/github.com_gobin-testrepos_simple-main_v1.0.0.txtar
diff --git a/cmd/txtar-c/savedir.go b/cmd/txtar-c/savedir.go
index 027871dd..07f0ab27 100644
--- a/cmd/txtar-c/savedir.go
+++ b/cmd/txtar-c/savedir.go
@@ -6,7 +6,7 @@
 //
 // Usage:
 //
-//	txtar-c /path/to/dir >saved.txt
+//	txtar-c /path/to/dir >saved.txtar
 //
 // See https://godoc.org/github.com/rogpeppe/go-internal/txtar for details of the format
 // and how to parse a txtar file.
@@ -30,7 +30,7 @@ import (
 var flag = stdflag.NewFlagSet(os.Args[0], stdflag.ContinueOnError)
 
 func usage() {
-	fmt.Fprintf(os.Stderr, "usage: txtar-c dir >saved.txt\n")
+	fmt.Fprintf(os.Stderr, "usage: txtar-c dir >saved.txtar\n")
 	flag.PrintDefaults()
 }
 
diff --git a/goproxytest/proxy.go b/goproxytest/proxy.go
index b4e82be8..05587603 100644
--- a/goproxytest/proxy.go
+++ b/goproxytest/proxy.go
@@ -7,9 +7,9 @@ Package goproxytest serves Go modules from a proxy server designed to run on
 localhost during tests, both to make tests avoid requiring specific network
 servers and also to make them significantly faster.
 
-Each module archive is either a file named path_vers.txt or a directory named
-path_vers, where slashes in path have been replaced with underscores. The
-archive or directory must contain two files ".info" and ".mod", to be served as
+Each module archive is either a file named path_vers.txtar or path_vers.txt, or
+a directory named path_vers, where slashes in path have been replaced with underscores.
+The archive or directory must contain two files ".info" and ".mod", to be served as
 the info and mod files in the proxy protocol (see
 https://research.swtch.com/vgo-module).  The remaining files are served as the
 content of the module zip file.  The path@vers prefix required of files in the
@@ -96,10 +96,15 @@ func (srv *Server) readModList() error {
 	}
 	for _, info := range infos {
 		name := info.Name()
-		if !strings.HasSuffix(name, ".txt") && !info.IsDir() {
+		switch {
+		case strings.HasSuffix(name, ".txt"):
+			name = strings.TrimSuffix(name, ".txt")
+		case strings.HasSuffix(name, ".txtar"):
+			name = strings.TrimSuffix(name, ".txtar")
+		case info.IsDir():
+		default:
 			continue
 		}
-		name = strings.TrimSuffix(name, ".txt")
 		i := strings.LastIndex(name, "_v")
 		if i < 0 {
 			continue
@@ -281,13 +286,17 @@ func (srv *Server) readArchive(path, vers string) *txtar.Archive {
 	}
 
 	prefix := strings.Replace(enc, "/", "_", -1)
-	name := filepath.Join(srv.dir, prefix+"_"+encVers+".txt")
+	name := filepath.Join(srv.dir, prefix+"_"+encVers)
+	txtName := name + ".txt"
+	txtarName := name + ".txtar"
 	a := srv.archiveCache.Do(name, func() interface{} {
-		a, err := txtar.ParseFile(name)
+		a, err := txtar.ParseFile(txtarName)
 		if os.IsNotExist(err) {
-			// we fallback to trying a directory
-			name = strings.TrimSuffix(name, ".txt")
-
+			// fall back to trying with the .txt extension
+			a, err = txtar.ParseFile(txtName)
+		}
+		if os.IsNotExist(err) {
+			// fall back to trying a directory
 			a = new(txtar.Archive)
 
 			err = filepath.Walk(name, func(path string, info os.FileInfo, err error) error {
diff --git a/testscript/doc.go b/testscript/doc.go
index ba91db36..10ae6ace 100644
--- a/testscript/doc.go
+++ b/testscript/doc.go
@@ -14,10 +14,10 @@ To invoke the tests, call testscript.Run. For example:
 		})
 	}
 
-A testscript directory holds test scripts *.txt run during 'go test'.
+A testscript directory holds test scripts with extension txtar or txt run during 'go test'.
 Each script defines a subtest; the exact set of allowable commands in a
 script are defined by the parameters passed to the Run function.
-To run a specific script foo.txt
+To run a specific script foo.txtar or foo.txt, run
 
 	go test cmd/go -run=TestName/^foo$
 
@@ -68,7 +68,7 @@ systems, ".exe" on Windows.
 The script's supporting files are unpacked relative to $WORK
 and then the script begins execution in that
 directory as well. Thus the example above runs in $WORK
-with $WORK/hello.txt containing the listed contents.
+with $WORK/hello.txtar containing the listed contents.
 
 The lines at the top of the script are a sequence of commands to be
 executed by a small script engine in the testscript package (not the system
diff --git a/testscript/testdata/testscript_update_script.txt b/testscript/testdata/testscript_update_script.txt
index b53e42fb..fe8e2a95 100644
--- a/testscript/testdata/testscript_update_script.txt
+++ b/testscript/testdata/testscript_update_script.txt
@@ -1,7 +1,13 @@
+# Check that we support both txt and txtar extensions.
+
 unquote scripts/testscript.txt
 unquote testscript-new.txt
+
+cp scripts/testscript.txt scripts/testscript2.txtar
+
 testscript -update scripts
 cmp scripts/testscript.txt testscript-new.txt
+cmp scripts/testscript2.txtar testscript-new.txt
 
 -- scripts/testscript.txt --
 >fprintargs stdout right
diff --git a/testscript/testscript.go b/testscript/testscript.go
index af752e3f..1bbd7ce1 100644
--- a/testscript/testscript.go
+++ b/testscript/testscript.go
@@ -108,8 +108,8 @@ func (e *Env) T() T {
 // Params holds parameters for a call to Run.
 type Params struct {
 	// Dir holds the name of the directory holding the scripts.
-	// All files in the directory with a .txt suffix will be considered
-	// as test scripts. By default the current directory is used.
+	// All files in the directory with a .txtar or .txt suffix will be
+	// considered as test scripts. By default the current directory is used.
 	// Dir is interpreted relative to the current test directory.
 	Dir string
 
@@ -158,7 +158,7 @@ type Params struct {
 }
 
 // RunDir runs the tests in the given directory. All files in dir with a ".txt"
-// are considered to be test files.
+// or ".txtar" extension are considered to be test files.
 func Run(t *testing.T, p Params) {
 	RunT(tshim{t}, p)
 }
@@ -200,13 +200,20 @@ func (t tshim) Verbose() bool {
 // RunT is like Run but uses an interface type instead of the concrete *testing.T
 // type to make it possible to use testscript functionality outside of go test.
 func RunT(t T, p Params) {
-	glob := filepath.Join(p.Dir, "*.txt")
-	files, err := filepath.Glob(glob)
+	entries, err := os.ReadDir(p.Dir)
 	if err != nil {
 		t.Fatal(err)
 	}
+	var files []string
+	for _, entry := range entries {
+		name := entry.Name()
+		if strings.HasSuffix(name, ".txtar") || strings.HasSuffix(name, ".txt") {
+			files = append(files, filepath.Join(p.Dir, name))
+		}
+	}
+
 	if len(files) == 0 {
-		t.Fatal(fmt.Sprintf("no scripts found matching glob: %v", glob))
+		t.Fatal(fmt.Sprintf("no txtar nor txt scripts found in dir %s", p.Dir))
 	}
 	testTempDir := p.WorkdirRoot
 	if testTempDir == "" {
diff --git a/testscript/testscript_test.go b/testscript/testscript_test.go
index 186b2218..fd7b2f29 100644
--- a/testscript/testscript_test.go
+++ b/testscript/testscript_test.go
@@ -312,7 +312,7 @@ func TestBadDir(t *testing.T) {
 	if got := len(ft.failMsgs); got != wantCount {
 		t.Fatalf("expected %v fail message; got %v", wantCount, got)
 	}
-	wantMsg := regexp.MustCompile(`no scripts found matching glob: thiswillnevermatch[/\\]\*\.txt`)
+	wantMsg := regexp.MustCompile(`open thiswillnevermatch: no such file or directory`)
 	if got := ft.failMsgs[0]; !wantMsg.MatchString(got) {
 		t.Fatalf("expected msg to match `%v`; got:\n%v", wantMsg, got)
 	}