diff --git a/git-codereview/branch_test.go b/git-codereview/branch_test.go
index d5b8a43..438ff39 100644
--- a/git-codereview/branch_test.go
+++ b/git-codereview/branch_test.go
@@ -14,17 +14,17 @@
 	gt := newGitTest(t)
 	defer gt.done()
 
-	t.Logf("on master")
-	checkCurrentBranch(t, "master", "origin/master", false, false, "", "")
+	t.Logf("on main")
+	checkCurrentBranch(t, "main", "origin/main", false, false, "", "")
 
 	t.Logf("on newbranch")
 	trun(t, gt.client, "git", "checkout", "--no-track", "-b", "newbranch")
-	checkCurrentBranch(t, "newbranch", "origin/master", true, false, "", "")
+	checkCurrentBranch(t, "newbranch", "origin/main", true, false, "", "")
 
 	t.Logf("making change")
 	write(t, gt.client+"/file", "i made a change", 0644)
 	trun(t, gt.client, "git", "commit", "-a", "-m", "My change line.\n\nChange-Id: I0123456789abcdef0123456789abcdef\n")
-	checkCurrentBranch(t, "newbranch", "origin/master", true, true, "I0123456789abcdef0123456789abcdef", "My change line.")
+	checkCurrentBranch(t, "newbranch", "origin/main", true, true, "I0123456789abcdef0123456789abcdef", "My change line.")
 
 	t.Logf("on dev.branch")
 	trun(t, gt.client, "git", "checkout", "-t", "-b", "dev.branch", "origin/dev.branch")
@@ -73,16 +73,16 @@
 	gt := newGitTest(t)
 	defer gt.done()
 
-	t.Logf("on master")
-	checkLocalBranches(t, "master")
+	t.Logf("on main")
+	checkLocalBranches(t, "main")
 
 	t.Logf("on dev branch")
 	trun(t, gt.client, "git", "checkout", "-b", "newbranch")
-	checkLocalBranches(t, "master", "newbranch")
+	checkLocalBranches(t, "main", "newbranch")
 
 	t.Logf("detached head mode")
 	trun(t, gt.client, "git", "checkout", "HEAD^0")
-	checkLocalBranches(t, "HEAD", "master", "newbranch")
+	checkLocalBranches(t, "HEAD", "main", "newbranch")
 }
 
 func checkLocalBranches(t *testing.T, want ...string) {
@@ -103,9 +103,9 @@
 
 	t.Logf("creating file paths that conflict with revision parameters")
 	mkdir(t, gt.client+"/origin")
-	write(t, gt.client+"/origin/master..work", "Uh-Oh! SpaghettiOs", 0644)
+	write(t, gt.client+"/origin/main..work", "Uh-Oh! SpaghettiOs", 0644)
 	mkdir(t, gt.client+"/work..origin")
-	write(t, gt.client+"/work..origin/master", "Be sure to drink your Ovaltine", 0644)
+	write(t, gt.client+"/work..origin/main", "Be sure to drink your Ovaltine", 0644)
 
 	b := CurrentBranch()
 	b.Submitted("I123456789")
@@ -159,12 +159,12 @@
 	gt := newGitTest(t)
 	defer gt.done()
 
-	// commit more work on master
+	// commit more work on main
 	write(t, gt.server+"/file", "more work", 0644)
 	trun(t, gt.server, "git", "commit", "-m", "work", "file")
 
 	// update client
-	trun(t, gt.client, "git", "checkout", "master")
+	trun(t, gt.client, "git", "checkout", "main")
 	trun(t, gt.client, "git", "pull")
 
 	hash := strings.TrimSpace(trun(t, gt.client, "git", "rev-parse", "HEAD"))
@@ -178,7 +178,7 @@
 	if bp != hash {
 		t.Logf("branches:\n%s", trun(t, gt.client, "git", "branch", "-a", "-v"))
 		t.Logf("log:\n%s", trun(t, gt.client, "git", "log", "--graph", "--decorate"))
-		t.Logf("log origin/master..HEAD:\n%s", trun(t, gt.client, "git", "log", "origin/master..HEAD"))
+		t.Logf("log origin/main..HEAD:\n%s", trun(t, gt.client, "git", "log", "origin/main..HEAD"))
 		t.Fatalf("branchpoint=%q, want %q", bp, hash)
 	}
 }
diff --git a/git-codereview/change_test.go b/git-codereview/change_test.go
index e9337dc..206ed82 100644
--- a/git-codereview/change_test.go
+++ b/git-codereview/change_test.go
@@ -14,28 +14,28 @@
 	gt := newGitTest(t)
 	defer gt.done()
 
-	t.Logf("master -> master")
-	testMain(t, "change", "master")
-	testRan(t, "git checkout -q master")
+	t.Logf("main -> main")
+	testMain(t, "change", "main")
+	testRan(t, "git checkout -q main")
 
 	testCommitMsg = "foo: my commit msg"
-	t.Logf("master -> work")
+	t.Logf("main -> work")
 	testMain(t, "change", "work")
 	testRan(t, "git checkout -q -b work",
-		"git branch -q --set-upstream-to origin/master")
+		"git branch -q --set-upstream-to origin/main")
 
-	t.Logf("work -> master")
-	testMain(t, "change", "master")
-	testRan(t, "git checkout -q master")
+	t.Logf("work -> main")
+	testMain(t, "change", "main")
+	testRan(t, "git checkout -q main")
 
-	t.Logf("master -> work with staged changes")
+	t.Logf("main -> work with staged changes")
 	write(t, gt.client+"/file", "new content", 0644)
 	trun(t, gt.client, "git", "add", "file")
 	testMain(t, "change", "work")
 	testRan(t, "git checkout -q work",
 		"git commit -q --allow-empty -m foo: my commit msg")
 
-	t.Logf("master -> dev.branch")
+	t.Logf("main -> dev.branch")
 	testMain(t, "change", "dev.branch")
 	testRan(t, "git checkout -q -t -b dev.branch origin/dev.branch")
 }
@@ -52,13 +52,13 @@
 	gt := newGitTest(t)
 	defer gt.done()
 
-	// commit to master (mistake)
+	// commit to main (mistake)
 	write(t, gt.client+"/file", "new content", 0644)
 	trun(t, gt.client, "git", "add", "file")
 	trun(t, gt.client, "git", "commit", "-m", "msg")
 
 	testMainDied(t, "change", "work")
-	testPrintedStderr(t, "bad repo state: branch master is ahead of origin/master")
+	testPrintedStderr(t, "bad repo state: branch main is ahead of origin/main")
 }
 
 func TestMessageRE(t *testing.T) {
@@ -117,7 +117,7 @@
 	// Ensure that 'change' with a CL accepts we have gerrit. Test address is injected by newGerritServer.
 	write(t, gt.server+"/codereview.cfg", "gerrit: on", 0644)
 	trun(t, gt.server, "git", "add", "codereview.cfg")
-	trun(t, gt.server, "git", "commit", "-m", "codereview.cfg on master")
+	trun(t, gt.server, "git", "commit", "-m", "codereview.cfg on main")
 	trun(t, gt.client, "git", "pull")
 	defer srv.done()
 
@@ -140,7 +140,7 @@
 	}})
 
 	checkChangeCL := func(arg, ref, hash string) {
-		testMain(t, "change", "master")
+		testMain(t, "change", "main")
 		testMain(t, "change", arg)
 		testRan(t,
 			fmt.Sprintf("git fetch -q origin %s", ref),
diff --git a/git-codereview/gofmt_test.go b/git-codereview/gofmt_test.go
index 0bd6aa9..81f82a4 100644
--- a/git-codereview/gofmt_test.go
+++ b/git-codereview/gofmt_test.go
@@ -255,33 +255,33 @@
 	gt := newGitTest(t)
 	defer gt.done()
 
-	// merge dev.branch into master
+	// merge dev.branch into main
 	write(t, gt.server+"/file", "more work", 0644)
 	trun(t, gt.server, "git", "commit", "-m", "work", "file")
 	trun(t, gt.server, "git", "merge", "-m", "merge", "dev.branch")
 
-	// add bad go file on master
+	// add bad go file on main
 	write(t, gt.server+"/bad.go", "package {\n", 0644)
 	trun(t, gt.server, "git", "add", "bad.go")
 	trun(t, gt.server, "git", "commit", "-m", "bad go")
 
 	// update client
-	trun(t, gt.client, "git", "checkout", "master")
+	trun(t, gt.client, "git", "checkout", "main")
 	trun(t, gt.client, "git", "pull")
 	testMain(t, "change", "dev.branch")
 	trun(t, gt.client, "git", "pull")
 
-	// merge master into dev.branch, fast forward merge
-	trun(t, gt.client, "git", "merge", "--ff-only", "master")
+	// merge main into dev.branch, fast forward merge
+	trun(t, gt.client, "git", "merge", "--ff-only", "main")
 
 	// verify that now client is in a state where just the tag is changing; there's no new commit.
-	masterHash := strings.TrimSpace(trun(t, gt.server, "git", "rev-parse", "master"))
+	mainHash := strings.TrimSpace(trun(t, gt.server, "git", "rev-parse", "main"))
 	devHash := strings.TrimSpace(trun(t, gt.client, "git", "rev-parse", "HEAD"))
 
-	if masterHash != devHash {
+	if mainHash != devHash {
 		t.Logf("branches:\n%s", trun(t, gt.client, "git", "branch", "-a", "-v"))
 		t.Logf("log:\n%s", trun(t, gt.client, "git", "log", "--graph", "--decorate"))
-		t.Fatalf("setup wrong - got different commit hashes on master and dev branch")
+		t.Fatalf("setup wrong - got different commit hashes on main and dev branch")
 	}
 
 	// check that gofmt finds nothing to do, ignoring the bad (but committed) file1.go.
diff --git a/git-codereview/hook_test.go b/git-codereview/hook_test.go
index e9dc1c3..d4ffbc4 100644
--- a/git-codereview/hook_test.go
+++ b/git-codereview/hook_test.go
@@ -210,10 +210,10 @@
 	}
 
 	// Master has no prefix.
-	testMain(t, "change", "master")
+	testMain(t, "change", "main")
 	checkPrefix("Test message.\n")
 
-	// Work branch from master has no prefix.
+	// Work branch from main has no prefix.
 	testMain(t, "change", "work")
 	checkPrefix("Test message.\n")
 }
diff --git a/git-codereview/mail_test.go b/git-codereview/mail_test.go
index c655b54..b754d3b 100644
--- a/git-codereview/mail_test.go
+++ b/git-codereview/mail_test.go
@@ -26,7 +26,7 @@
 
 	testMain(t, "mail")
 	testRan(t,
-		"git push -q origin HEAD:refs/for/master",
+		"git push -q origin HEAD:refs/for/main",
 		"git tag -f work.mailed "+h)
 }
 
@@ -153,14 +153,14 @@
 	h := CurrentBranch().Pending()[1].ShortHash
 	testMain(t, "mail", "HEAD^")
 	testRan(t,
-		"git push -q origin "+h+":refs/for/master",
+		"git push -q origin "+h+":refs/for/main",
 		"git tag -f work.mailed "+h)
 
 	// Mail HEAD.
 	h = CurrentBranch().Pending()[0].ShortHash
 	testMain(t, "mail", "HEAD")
 	testRan(t,
-		"git push -q origin HEAD:refs/for/master",
+		"git push -q origin HEAD:refs/for/main",
 		"git tag -f work.mailed "+h)
 }
 
@@ -203,17 +203,17 @@
 
 	testMain(t, "mail")
 	testRan(t,
-		"git push -q origin HEAD:refs/for/master",
+		"git push -q origin HEAD:refs/for/main",
 		"git tag -f work.mailed "+h)
 
 	testMain(t, "mail", "-r", "r1")
 	testRan(t,
-		"git push -q origin HEAD:refs/for/master%r=r1@golang.org",
+		"git push -q origin HEAD:refs/for/main%r=r1@golang.org",
 		"git tag -f work.mailed "+h)
 
 	testMain(t, "mail", "-r", "other,anon", "-cc", "r1,full@email.com")
 	testRan(t,
-		"git push -q origin HEAD:refs/for/master%r=other@golang.org,r=anon@golang.org,cc=r1@golang.org,cc=full@email.com",
+		"git push -q origin HEAD:refs/for/main%r=other@golang.org,r=anon@golang.org,cc=r1@golang.org,cc=full@email.com",
 		"git tag -f work.mailed "+h)
 
 	testMainDied(t, "mail", "-r", "other", "-r", "anon,r1,missing")
@@ -229,7 +229,7 @@
 
 	testMain(t, "mail", "-wip")
 	testRan(t,
-		"git push -q origin HEAD:refs/for/master%wip",
+		"git push -q origin HEAD:refs/for/main%wip",
 		"git tag -f work.mailed "+h)
 }
 
@@ -253,7 +253,7 @@
 
 	testMain(t, "mail", "-topic", "test-topic")
 	testRan(t,
-		"git push -q origin HEAD:refs/for/master%topic=test-topic",
+		"git push -q origin HEAD:refs/for/main%topic=test-topic",
 		"git tag -f work.mailed "+h)
 }
 
@@ -274,11 +274,11 @@
 
 	testMain(t, "mail", "-hashtag", "test1,test2")
 	testRan(t,
-		"git push -q origin HEAD:refs/for/master%hashtag=test1,hashtag=test2",
+		"git push -q origin HEAD:refs/for/main%hashtag=test1,hashtag=test2",
 		"git tag -f work.mailed "+h)
 	testMain(t, "mail", "-hashtag", "")
 	testRan(t,
-		"git push -q origin HEAD:refs/for/master",
+		"git push -q origin HEAD:refs/for/main",
 		"git tag -f work.mailed "+h)
 
 	testMainDied(t, "mail", "-hashtag", "test1,,test3")
@@ -299,7 +299,7 @@
 
 	testMain(t, "change", "work")
 	testRan(t, "git checkout -q -b work",
-		"git branch -q --set-upstream-to origin/master")
+		"git branch -q --set-upstream-to origin/main")
 
 	t.Logf("creating empty change")
 	testCommitMsg = "foo: this commit will be empty"
diff --git a/git-codereview/pending.go b/git-codereview/pending.go
index bd8d508..e17a905 100644
--- a/git-codereview/pending.go
+++ b/git-codereview/pending.go
@@ -247,7 +247,7 @@
 		if n := b.CommitsBehind(); n > 0 {
 			tags = append(tags, fmt.Sprintf("%d behind", n))
 		}
-		if b.OriginBranch() != "origin/master" {
+		if br := b.OriginBranch(); br != "origin/master" && br != "origin/main" {
 			tags = append(tags, "tracking "+strings.TrimPrefix(b.OriginBranch(), "origin/"))
 		}
 		if len(tags) > 0 {
diff --git a/git-codereview/pending_test.go b/git-codereview/pending_test.go
index ee5e947..ccb2f76 100644
--- a/git-codereview/pending_test.go
+++ b/git-codereview/pending_test.go
@@ -22,7 +22,7 @@
 	defer gt.done()
 
 	testPending(t, `
-		master (current branch)
+		main (current branch)
 
 	`)
 }
@@ -69,13 +69,13 @@
 	trun(t, gt.server, "git", "commit", "-a", "-m", "v3")
 
 	trun(t, gt.client, "git", "fetch")
-	trun(t, gt.client, "git", "checkout", "-b", "work3ignored", "-t", "origin/master")
+	trun(t, gt.client, "git", "checkout", "-b", "work3ignored", "-t", "origin/main")
 
 	write(t, gt.server+"/file", "v4", 0644)
 	trun(t, gt.server, "git", "commit", "-a", "-m", "v4")
 
 	trun(t, gt.client, "git", "fetch")
-	trun(t, gt.client, "git", "checkout", "-b", "work2", "-t", "origin/master")
+	trun(t, gt.client, "git", "checkout", "-b", "work2", "-t", "origin/main")
 	write(t, gt.client+"/file", "modify", 0644)
 	write(t, gt.client+"/file1", "new", 0644)
 	trun(t, gt.client, "git", "add", "file", "file1")
@@ -159,14 +159,14 @@
 	gt.enableGerrit(t)
 	defer gt.done()
 
-	trun(t, gt.client, "git", "checkout", "master")
+	trun(t, gt.client, "git", "checkout", "main")
 	write(t, gt.client+"/file", "v3", 0644)
 	trun(t, gt.client, "git", "commit", "-a", "-m", "v3")
 
 	testPending(t, `
-		master REVHASH..REVHASH (current branch)
-			ERROR: Branch contains 1 commit not on origin/master.
-				Do not commit directly to master branch.
+		main REVHASH..REVHASH (current branch)
+			ERROR: Branch contains 1 commit not on origin/main.
+				Do not commit directly to main branch.
 		
 		+ REVHASH
 			v3
@@ -177,9 +177,9 @@
 	`)
 
 	testPendingArgs(t, []string{"-s"}, `
-		master REVHASH..REVHASH (current branch)
-			ERROR: Branch contains 1 commit not on origin/master.
-				Do not commit directly to master branch.
+		main REVHASH..REVHASH (current branch)
+			ERROR: Branch contains 1 commit not on origin/main.
+				Do not commit directly to main branch.
 		+ REVHASH v3
 
 	`)
@@ -446,7 +446,7 @@
 
 func testPendingReply(srv *gerritServer, id, rev, status string) {
 	srv.setJSON(id, `{
-		"id": "proj~master~`+id+`",
+		"id": "proj~main~`+id+`",
 		"project": "proj",
 		"current_revision": "`+rev+`",
 		"status": "`+status+`",
diff --git a/git-codereview/submit_test.go b/git-codereview/submit_test.go
index 3f893ec..fbe2cb3 100644
--- a/git-codereview/submit_test.go
+++ b/git-codereview/submit_test.go
@@ -94,9 +94,9 @@
 	t.Logf("> submit with unexpected status")
 	const newJSON = `{"status": "NEW", "labels": {"Code-Review": {"approved": {}}}}`
 	srv.setJSON(id, newJSON)
-	srv.setReply("/a/changes/proj~master~I123456789/submit", gerritReply{body: ")]}'\n" + newJSON})
+	srv.setReply("/a/changes/proj~main~I123456789/submit", gerritReply{body: ")]}'\n" + newJSON})
 	testMainDied(t, "submit")
-	testRan(t, "git push -q origin HEAD:refs/for/master")
+	testRan(t, "git push -q origin HEAD:refs/for/main")
 	testPrintedStderr(t, "submit error: unexpected post-submit Gerrit change status \"NEW\"")
 }
 
@@ -109,15 +109,15 @@
 	gt.work(t)
 
 	setJSON := func(json string) {
-		srv.setReply("/a/changes/proj~master~I123456789", gerritReply{body: ")]}'\n" + json})
+		srv.setReply("/a/changes/proj~main~I123456789", gerritReply{body: ")]}'\n" + json})
 	}
 
 	t.Log("> submit with timeout")
 	const submittedJSON = `{"status": "SUBMITTED", "mergeable": true, "labels": {"Code-Review": {"approved": {}}}}`
 	setJSON(submittedJSON)
-	srv.setReply("/a/changes/proj~master~I123456789/submit", gerritReply{body: ")]}'\n" + submittedJSON})
+	srv.setReply("/a/changes/proj~main~I123456789/submit", gerritReply{body: ")]}'\n" + submittedJSON})
 	testMainDied(t, "submit")
-	testRan(t, "git push -q origin HEAD:refs/for/master")
+	testRan(t, "git push -q origin HEAD:refs/for/main")
 	testPrintedStderr(t, "cannot submit: timed out waiting for change to be submitted by Gerrit")
 }
 
@@ -144,7 +144,7 @@
 	)
 	submitted := false
 	npoll := 0
-	srv.setReply("/a/changes/proj~master~I123456789", gerritReply{f: func() gerritReply {
+	srv.setReply("/a/changes/proj~main~I123456789", gerritReply{f: func() gerritReply {
 		if !submitted {
 			return gerritReply{body: ")]}'\n" + newJSON}
 		}
@@ -153,7 +153,7 @@
 		}
 		return gerritReply{body: ")]}'\n" + mergedJSON}
 	}})
-	srv.setReply("/a/changes/proj~master~I123456789/submit", gerritReply{f: func() gerritReply {
+	srv.setReply("/a/changes/proj~main~I123456789/submit", gerritReply{f: func() gerritReply {
 		if submitted {
 			return gerritReply{status: 409}
 		}
@@ -235,20 +235,20 @@
 		Labels:          map[string]*GerritLabel{"Code-Review": &GerritLabel{Approved: new(GerritAccount)}},
 	}
 
-	srv.setReply("/a/changes/proj~master~I0000001", gerritReply{f: func() gerritReply {
+	srv.setReply("/a/changes/proj~main~I0000001", gerritReply{f: func() gerritReply {
 		return gerritReply{json: cl1}
 	}})
-	srv.setReply("/a/changes/proj~master~I0000001/submit", gerritReply{f: func() gerritReply {
+	srv.setReply("/a/changes/proj~main~I0000001/submit", gerritReply{f: func() gerritReply {
 		if cl1.Status != "NEW" {
 			return gerritReply{status: 409}
 		}
 		cl1.Status = "MERGED"
 		return gerritReply{json: cl1}
 	}})
-	srv.setReply("/a/changes/proj~master~I0000002", gerritReply{f: func() gerritReply {
+	srv.setReply("/a/changes/proj~main~I0000002", gerritReply{f: func() gerritReply {
 		return gerritReply{json: cl2}
 	}})
-	srv.setReply("/a/changes/proj~master~I0000002/submit", gerritReply{f: func() gerritReply {
+	srv.setReply("/a/changes/proj~main~I0000002/submit", gerritReply{f: func() gerritReply {
 		if cl2.Status != "NEW" {
 			return gerritReply{status: 409}
 		}
diff --git a/git-codereview/util_test.go b/git-codereview/util_test.go
index 8acdb66..90a5b93 100644
--- a/git-codereview/util_test.go
+++ b/git-codereview/util_test.go
@@ -83,7 +83,7 @@
 	t.Helper()
 	if gt.nwork == 0 {
 		trun(t, gt.client, "git", "checkout", "-b", "work")
-		trun(t, gt.client, "git", "branch", "--set-upstream-to", "origin/master")
+		trun(t, gt.client, "git", "branch", "--set-upstream-to", "origin/main")
 		trun(t, gt.client, "git", "tag", "work") // make sure commands do the right thing when there is a tag of the same name
 	}
 
@@ -142,22 +142,35 @@
 	server := tmpdir + "/git-origin"
 
 	mkdir(t, server)
-	write(t, server+"/file", "this is master", 0644)
+	write(t, server+"/file", "this is main", 0644)
 	write(t, server+"/.gitattributes", "* -text\n", 0644)
 	trun(t, server, "git", "init", ".")
 	trun(t, server, "git", "config", "user.name", "gopher")
 	trun(t, server, "git", "config", "user.email", "gopher@example.com")
 	trun(t, server, "git", "add", "file", ".gitattributes")
-	trun(t, server, "git", "commit", "-m", "on master")
+	trun(t, server, "git", "commit", "-m", "initial commit")
+
+	// Newer gits use a default branch name of main.
+	// Older ones used master.
+	// So the branch name now may be main or master.
+	// We would like to assume main for the tests.
+	// Newer gits would let us do
+	//	git init --initial-branch=main .
+	// above, but older gits don't have initial-branch.
+	// And we don't trust older gits to handle a no-op branch rename.
+	// So rename it to something different, and then to main.
+	// Then we'll be in a known state.
+	trun(t, server, "git", "branch", "-M", "certainly-not-main")
+	trun(t, server, "git", "branch", "-M", "main")
 
 	for _, name := range []string{"dev.branch", "release.branch"} {
-		trun(t, server, "git", "checkout", "master")
+		trun(t, server, "git", "checkout", "main")
 		trun(t, server, "git", "checkout", "-b", name)
 		write(t, server+"/file."+name, "this is "+name, 0644)
 		trun(t, server, "git", "add", "file."+name)
 		trun(t, server, "git", "commit", "-m", "on "+name)
 	}
-	trun(t, server, "git", "checkout", "master")
+	trun(t, server, "git", "checkout", "main")
 
 	client := tmpdir + "/git-client"
 	mkdir(t, client)
@@ -439,7 +452,7 @@
 }
 
 func (s *gerritServer) setJSON(id, json string) {
-	s.setReply("/a/changes/proj~master~"+id, gerritReply{body: ")]}'\n" + json})
+	s.setReply("/a/changes/proj~main~"+id, gerritReply{body: ")]}'\n" + json})
 }
 
 func (s *gerritServer) ServeHTTP(w http.ResponseWriter, req *http.Request) {