diff --git a/internal/fetch/latest_test.go b/internal/fetch/latest_test.go
index ab7560c..a4c6113 100644
--- a/internal/fetch/latest_test.go
+++ b/internal/fetch/latest_test.go
@@ -30,7 +30,7 @@
 	}{
 		{"example.com/basic", "v1.1.0", "v1.1.0"},
 		{"example.com/retractions", "v1.2.0", "v1.0.0"},
-		{"std", "v1.14.6", "v1.14.6"},
+		{"std", "v1.21.0", "v1.21.0"},
 	} {
 		got, err := LatestModuleVersions(context.Background(), test.modulePath, prox, nil)
 		if err != nil {
diff --git a/internal/frontend/versions.go b/internal/frontend/versions.go
index 454e242..3ede9e9 100644
--- a/internal/frontend/versions.go
+++ b/internal/frontend/versions.go
@@ -396,10 +396,10 @@
 func linkVersion(modulePath, requestedVersion, resolvedVersion string) string {
 	if modulePath == stdlib.ModulePath {
 		if strings.HasPrefix(resolvedVersion, "go") {
-			return resolvedVersion
+			return resolvedVersion // already a go version
 		}
 		if stdlib.SupportedBranches[requestedVersion] {
-			return requestedVersion
+			return requestedVersion // branch, not version
 		}
 		return goTagForVersion(resolvedVersion)
 	}
diff --git a/internal/frontend/versions_test.go b/internal/frontend/versions_test.go
index 1ed90a5..31efad6 100644
--- a/internal/frontend/versions_test.go
+++ b/internal/frontend/versions_test.go
@@ -34,14 +34,18 @@
 	return m
 }
 
-func versionSummaries(path string, versions []string, linkify func(path, version string) string) []*VersionSummary {
+func versionSummaries(path string, versions []string, isStdlib bool, linkify func(path, version string) string) []*VersionSummary {
 	vs := make([]*VersionSummary, len(versions))
 	for i, version := range versions {
+		semver := version
+		if isStdlib {
+			semver = stdlib.VersionForTag(version)
+		}
 		vs[i] = &VersionSummary{
 			Version:    version,
 			Link:       linkify(path, version),
 			CommitTime: absoluteTime(sample.CommitTime),
-			IsMinor:    isMinor(version),
+			IsMinor:    isMinor(semver),
 		}
 	}
 	return vs
@@ -80,10 +84,10 @@
 			true),
 		Documentation: []*internal.Documentation{sample.Doc},
 	}
-	makeList := func(pkgPath, modulePath, major string, versions []string, incompatible bool) *VersionList {
+	makeList := func(pkgPath, modulePath, major string, versions []string, isStdlib, incompatible bool) *VersionList {
 		return &VersionList{
 			VersionListKey: VersionListKey{ModulePath: modulePath, Major: major, Incompatible: incompatible},
-			Versions: versionSummaries(pkgPath, versions, func(path, version string) string {
+			Versions: versionSummaries(pkgPath, versions, isStdlib, func(path, version string) string {
 				return constructUnitURL(pkgPath, modulePath, version)
 			}),
 		}
@@ -114,6 +118,12 @@
 		t.Fatal(err)
 	}
 
+	// Named bool values, for readability of call sites below.
+	const (
+		stdlib, notStdlib        = true, false
+		compatible, incompatible = false, true
+	)
+
 	for _, tc := range []struct {
 		name        string
 		pkg         *internal.Unit
@@ -124,12 +134,25 @@
 			name: "want stdlib versions",
 			pkg:  nethttpPkg,
 			modules: []*internal.Module{
+				sampleModule("std", "v1.22.0-rc.1", version.TypePseudo, nethttpPkg),
+				sampleModule("std", "v1.21.0", version.TypeRelease, nethttpPkg),
+				sampleModule("std", "v1.20.0", version.TypeRelease, nethttpPkg),
 				sampleModule("std", "v1.12.5", version.TypeRelease, nethttpPkg),
 				sampleModule("std", "v1.11.6", version.TypeRelease, nethttpPkg),
 			},
 			wantDetails: &VersionsDetails{
 				ThisModule: []*VersionList{
-					makeList("net/http", "std", "go1", []string{"go1.12.5", "go1.11.6"}, false),
+					makeList(
+						"net/http", "std", "go1",
+						[]string{
+							"go1.22rc1",
+							"go1.21.0",
+							"go1.20",
+							"go1.12.5",
+							"go1.11.6",
+						},
+						stdlib, compatible,
+					),
 				},
 			},
 		},
@@ -149,7 +172,7 @@
 			wantDetails: &VersionsDetails{
 				ThisModule: []*VersionList{
 					func() *VersionList {
-						vl := makeList(v1Path, modulePath1, "v1", []string{"v1.3.0", "v1.2.3", "v1.2.1"}, false)
+						vl := makeList(v1Path, modulePath1, "v1", []string{"v1.3.0", "v1.2.3", "v1.2.1"}, notStdlib, compatible)
 						vl.Versions[2].Vulns = []vuln.Vuln{{
 							ID:      vulnEntry.ID,
 							Details: vulnEntry.Summary,
@@ -158,7 +181,7 @@
 					}(),
 				},
 				IncompatibleModules: []*VersionList{
-					makeList(v1Path, modulePath1, "v2", []string{"v2.1.0+incompatible"}, true),
+					makeList(v1Path, modulePath1, "v2", []string{"v2.1.0+incompatible"}, notStdlib, incompatible),
 				},
 				OtherModules: []string{"test.com", modulePath2},
 			},
@@ -176,7 +199,7 @@
 			},
 			wantDetails: &VersionsDetails{
 				ThisModule: []*VersionList{
-					makeList(v2Path, modulePath2, "v2", []string{"v2.2.1-alpha.1", "v2.0.0"}, false),
+					makeList(v2Path, modulePath2, "v2", []string{"v2.2.1-alpha.1", "v2.0.0"}, notStdlib, compatible),
 				},
 				OtherModules: []string{modulePath1},
 			},
diff --git a/internal/stdlib/gorepo.go b/internal/stdlib/gorepo.go
index 6bb2077..09ee8ca 100644
--- a/internal/stdlib/gorepo.go
+++ b/internal/stdlib/gorepo.go
@@ -161,6 +161,7 @@
 	"refs/tags/go1.13",
 	"refs/tags/go1.13beta1",
 	"refs/tags/go1.14.6",
+	"refs/tags/go1.21.0",
 	"refs/heads/dev.fuzz",
 	"refs/heads/master",
 	// other tags
diff --git a/internal/stdlib/stdlib.go b/internal/stdlib/stdlib.go
index b7fa93b..b11a0a8 100644
--- a/internal/stdlib/stdlib.go
+++ b/internal/stdlib/stdlib.go
@@ -101,6 +101,9 @@
 // TagForVersion returns the Go standard library repository tag corresponding
 // to semver. The Go tags differ from standard semantic versions in a few ways,
 // such as beginning with "go" instead of "v".
+//
+// Starting with go1.21.0, the first patch release of major go versions include
+// the .0 suffix. Previously, the .0 suffix was elided (golang/go#57631).
 func TagForVersion(v string) (_ string, err error) {
 	defer derrors.Wrap(&err, "TagForVersion(%q)", v)
 
@@ -122,7 +125,9 @@
 	prerelease := semver.Prerelease(goVersion)
 	versionWithoutPrerelease := strings.TrimSuffix(goVersion, prerelease)
 	patch := strings.TrimPrefix(versionWithoutPrerelease, semver.MajorMinor(goVersion)+".")
-	if patch == "0" {
+	if patch == "0" && (semver.Compare(v, "v1.21.0") < 0 || prerelease != "") {
+		// Starting with go1.21.0, the first patch version includes .0.
+		// Prereleases do not include .0 (we don't do prereleases for other patch releases).
 		versionWithoutPrerelease = strings.TrimSuffix(versionWithoutPrerelease, ".0")
 	}
 	goVersion = fmt.Sprintf("go%s", strings.TrimPrefix(versionWithoutPrerelease, "v"))
@@ -251,10 +256,11 @@
 	return plumbing.NewTagReferenceName(tag), nil
 }
 
-// Versions returns all the versions of Go that are relevant to the discovery
-// site. These are all release versions (tags of the forms "goN.N" and
-// "goN.N.N", where N is a number) and beta or rc versions (tags of the forms
-// "goN.NbetaN" and "goN.N.NbetaN", and similarly for "rc" replacing "beta").
+// Versions returns all the semantic versions of Go that are relevant to the
+// discovery site. These are all release versions (derived from tags of the
+// forms "goN.N" and "goN.N.N", where N is a number) and beta or rc versions
+// (derived from tags of the forms "goN.NbetaN" and "goN.N.NbetaN", and
+// similarly for "rc" replacing "beta").
 func Versions() (_ []string, err error) {
 	defer derrors.Wrap(&err, "stdlib.Versions()")
 
diff --git a/internal/stdlib/stdlib_test.go b/internal/stdlib/stdlib_test.go
index 8841b0a..7425150 100644
--- a/internal/stdlib/stdlib_test.go
+++ b/internal/stdlib/stdlib_test.go
@@ -64,6 +64,26 @@
 			want:    "go1.13",
 		},
 		{
+			name:    "version v1.20.0-rc.2",
+			version: "v1.20.0-rc.2",
+			want:    "go1.20rc2",
+		},
+		{
+			name:    "version v1.20.0",
+			version: "v1.20.0",
+			want:    "go1.20",
+		},
+		{
+			name:    "version v1.21.0-rc.2",
+			version: "v1.21.0-rc.2",
+			want:    "go1.21rc2",
+		},
+		{
+			name:    "version v1.21.0",
+			version: "v1.21.0",
+			want:    "go1.21.0",
+		},
+		{
 			name:    "master branch",
 			version: "master",
 			want:    "master",
@@ -96,7 +116,7 @@
 				return
 			}
 			if got != test.want {
-				t.Errorf("TagForVersion(%q) = %q, %v, wanted %q, %v", test.version, got, err, test.want, nil)
+				t.Fatalf("TagForVersion(%q) = %q, %v, wanted %q, %v", test.version, got, err, test.want, nil)
 			}
 		})
 	}
@@ -236,7 +256,7 @@
 	}{
 		{
 			requestedVersion: "latest",
-			want:             "v1.14.6",
+			want:             "v1.21.0",
 		},
 		{
 			requestedVersion: "master",
@@ -279,7 +299,8 @@
 	otherWants := append([]string{"v1.17.6"}, commonWants...)
 	t.Run("test", func(t *testing.T) {
 		defer WithTestData()()
-		testVersions(commonWants)
+		testWants := append([]string{"v1.21.0"}, commonWants...)
+		testVersions(testWants)
 	})
 	t.Run("local", func(t *testing.T) {
 		if *repoPath == "" {
@@ -316,6 +337,8 @@
 		{"go1.0", ""},
 		{"weekly.2012-02-14", ""},
 		{"latest", "latest"},
+		{"go1.21.0", "v1.21.0"},
+		{"go1.21", "v1.21.0"},
 	} {
 		got := VersionForTag(test.in)
 		if got != test.want {