diff --git a/LICENSE b/LICENSE
index 66284d31a..394db19e4 100644
--- a/LICENSE
+++ b/LICENSE
@@ -1,7 +1,6 @@
 BSD 3-Clause License
 
-Copyright (c) 2020 Tailscale & AUTHORS.
-All rights reserved.
+Copyright (c) 2020 Tailscale Inc & AUTHORS.
 
 Redistribution and use in source and binary forms, with or without
 modification, are permitted provided that the following conditions are met:
diff --git a/cmd/addlicense/main.go b/cmd/addlicense/main.go
index 856bc8b86..a8fd9dd4a 100644
--- a/cmd/addlicense/main.go
+++ b/cmd/addlicense/main.go
@@ -14,26 +14,24 @@ import (
 )
 
 var (
-	year = flag.Int("year", 0, "copyright year")
 	file = flag.String("file", "", "file to modify")
 )
 
 func usage() {
 	fmt.Fprintf(os.Stderr, `
-usage: addlicense -year YEAR -file FILE <subcommand args...>
+usage: addlicense -file FILE <subcommand args...>
 `[1:])
 
 	flag.PrintDefaults()
 	fmt.Fprintf(os.Stderr, `
-addlicense adds a Tailscale license to the beginning of file,
-using year as the copyright year.
+addlicense adds a Tailscale license to the beginning of file.
 
 It is intended for use with 'go generate', so it also runs a subcommand,
 which presumably creates the file.
 
 Sample usage:
 
-addlicense -year 2021 -file pull_strings.go stringer -type=pull
+addlicense -file pull_strings.go stringer -type=pull
 `[1:])
 	os.Exit(2)
 }
@@ -53,7 +51,7 @@ func main() {
 	check(err)
 	f, err := os.OpenFile(*file, os.O_TRUNC|os.O_WRONLY, 0644)
 	check(err)
-	_, err = fmt.Fprintf(f, license, *year)
+	_, err = fmt.Fprint(f, license)
 	check(err)
 	_, err = f.Write(b)
 	check(err)
@@ -69,8 +67,7 @@ func check(err error) {
 }
 
 var license = `
-// Copyright (c) %d Tailscale Inc & AUTHORS All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
 
 `[1:]
diff --git a/cmd/cloner/cloner.go b/cmd/cloner/cloner.go
index 37c8a30a5..11ee55078 100644
--- a/cmd/cloner/cloner.go
+++ b/cmd/cloner/cloner.go
@@ -79,7 +79,7 @@ func main() {
 		w("}")
 	}
 	cloneOutput := pkg.Name + "_clone.go"
-	if err := codegen.WritePackageFile("tailscale.com/cmd/cloner", pkg, cloneOutput, codegen.CopyrightYear("."), it, buf); err != nil {
+	if err := codegen.WritePackageFile("tailscale.com/cmd/cloner", pkg, cloneOutput, it, buf); err != nil {
 		log.Fatal(err)
 	}
 }
diff --git a/cmd/viewer/viewer.go b/cmd/viewer/viewer.go
index 058d107fc..0dc0b1dfb 100644
--- a/cmd/viewer/viewer.go
+++ b/cmd/viewer/viewer.go
@@ -383,7 +383,7 @@ func main() {
 		genView(buf, it, typ, pkg.Types)
 	}
 	out := pkg.Name + "_view.go"
-	if err := codegen.WritePackageFile("tailscale/cmd/viewer", pkg, out, codegen.CopyrightYear("."), it, buf); err != nil {
+	if err := codegen.WritePackageFile("tailscale/cmd/viewer", pkg, out, it, buf); err != nil {
 		log.Fatal(err)
 	}
 	if runCloner {
diff --git a/derp/derp_server.go b/derp/derp_server.go
index 1f1c22650..7714943cb 100644
--- a/derp/derp_server.go
+++ b/derp/derp_server.go
@@ -955,7 +955,7 @@ func (c *sclient) handleFrameSendPacket(ft frameType, fl uint32) error {
 // dropReason is why we dropped a DERP frame.
 type dropReason int
 
-//go:generate go run tailscale.com/cmd/addlicense -year 2021 -file dropreason_string.go go run golang.org/x/tools/cmd/stringer -type=dropReason -trimprefix=dropReason
+//go:generate go run tailscale.com/cmd/addlicense -file dropreason_string.go go run golang.org/x/tools/cmd/stringer -type=dropReason -trimprefix=dropReason
 
 const (
 	dropReasonUnknownDest      dropReason = iota // unknown destination pubkey
diff --git a/net/portmapper/pcp.go b/net/portmapper/pcp.go
index 455b7f471..c1d62b02b 100644
--- a/net/portmapper/pcp.go
+++ b/net/portmapper/pcp.go
@@ -17,7 +17,7 @@ import (
 // https://www.rfc-editor.org/rfc/pdfrfc/rfc6887.txt.pdf
 // https://tools.ietf.org/html/rfc6887
 
-//go:generate go run tailscale.com/cmd/addlicense -year 2021 -file pcpresultcode_string.go go run golang.org/x/tools/cmd/stringer -type=pcpResultCode -trimprefix=pcpCode
+//go:generate go run tailscale.com/cmd/addlicense -file pcpresultcode_string.go go run golang.org/x/tools/cmd/stringer -type=pcpResultCode -trimprefix=pcpCode
 
 type pcpResultCode uint8
 
diff --git a/net/portmapper/portmapper.go b/net/portmapper/portmapper.go
index 2e3fdacf1..8cb565b68 100644
--- a/net/portmapper/portmapper.go
+++ b/net/portmapper/portmapper.go
@@ -586,7 +586,7 @@ func (c *Client) createOrGetMapping(ctx context.Context) (external netip.AddrPor
 	}
 }
 
-//go:generate go run tailscale.com/cmd/addlicense -year 2021 -file pmpresultcode_string.go go run golang.org/x/tools/cmd/stringer -type=pmpResultCode -trimprefix=pmpCode
+//go:generate go run tailscale.com/cmd/addlicense -file pmpresultcode_string.go go run golang.org/x/tools/cmd/stringer -type=pmpResultCode -trimprefix=pmpCode
 
 type pmpResultCode uint16
 
diff --git a/scripts/check_license_headers.sh b/scripts/check_license_headers.sh
index 8b9cbbc30..89a243b63 100755
--- a/scripts/check_license_headers.sh
+++ b/scripts/check_license_headers.sh
@@ -9,17 +9,14 @@
 check_file() {
     got=$1
 
-    for year in `seq 2019 2023`; do
-        want=$(cat <<EOF
-// Copyright (c) $year Tailscale Inc & AUTHORS All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
+    want=$(cat <<EOF
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
 EOF
-        )
-        if [ "$got" = "$want" ]; then
-            return 0
-        fi
-    done
+    )
+    if [ "$got" = "$want" ]; then
+        return 0
+    fi
     return 1
 }
 
@@ -50,7 +47,7 @@ for file in $(find $1 -name '*.go' -not -path '*/.git/*'); do
             # Generated syscall wrappers
         ;;
         *)
-            header="$(head -3 $file)"
+            header="$(head -2 $file)"
             if ! check_file "$header"; then
                 fail=1
                 echo "${file#$1/} doesn't have the right copyright header:"
diff --git a/tstest/integration/gen_deps.go b/tstest/integration/gen_deps.go
index d31f175d6..23bb95ee5 100644
--- a/tstest/integration/gen_deps.go
+++ b/tstest/integration/gen_deps.go
@@ -35,9 +35,8 @@ func generate(goos string) {
 		log.Fatal(err)
 	}
 	var out bytes.Buffer
-	out.WriteString(`// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
+	out.WriteString(`// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
 
 // Code generated by gen_deps.go; DO NOT EDIT.
 
diff --git a/tstest/integration/vms/gen/test_codegen.go b/tstest/integration/vms/gen/test_codegen.go
index a7bc596c9..4fc108c73 100644
--- a/tstest/integration/vms/gen/test_codegen.go
+++ b/tstest/integration/vms/gen/test_codegen.go
@@ -7,10 +7,8 @@ package main
 
 import (
 	_ "embed"
-	"fmt"
 	"log"
 	"os"
-	"time"
 
 	"github.com/dave/jennifer/jen"
 	"github.com/iancoleman/strcase"
@@ -41,9 +39,8 @@ func main() {
 	}
 	defer fout.Close()
 
-	fmt.Fprintf(fout, "// Copyright (c) %d Tailscale Inc & AUTHORS All rights reserved.\n", time.Now().Year())
-	fout.WriteString("// Use of this source code is governed by a BSD-style\n")
-	fout.WriteString("// license that can be found in the LICENSE file.\n")
+	fout.WriteString("// Copyright (c) Tailscale Inc & AUTHORS\n")
+	fout.WriteString("// SPDX-License-Identifier: BSD-3-Clause\n")
 	fout.WriteString("\n")
 	fout.WriteString("// +build linux\n\n")
 
diff --git a/util/codegen/codegen.go b/util/codegen/codegen.go
index f35450810..364a9b69e 100644
--- a/util/codegen/codegen.go
+++ b/util/codegen/codegen.go
@@ -5,7 +5,6 @@
 package codegen
 
 import (
-	"bufio"
 	"bytes"
 	"fmt"
 	"go/ast"
@@ -13,16 +12,12 @@ import (
 	"go/types"
 	"io"
 	"os"
-	"path/filepath"
 	"reflect"
-	"regexp"
-	"strconv"
 	"strings"
 
 	"golang.org/x/tools/go/packages"
 	"golang.org/x/tools/imports"
 	"tailscale.com/util/mak"
-	"tailscale.com/util/must"
 )
 
 // LoadTypes returns all named types in pkgName, keyed by their type name.
@@ -57,9 +52,8 @@ func HasNoClone(structTag string) bool {
 	return false
 }
 
-const copyrightHeader = `// Copyright (c) %d Tailscale Inc & AUTHORS All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
+const copyrightHeader = `// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
 
 `
 
@@ -109,18 +103,16 @@ func (it *ImportTracker) Write(w io.Writer) {
 	fmt.Fprintf(w, ")\n\n")
 }
 
-func writeHeader(w io.Writer, tool, pkg string, copyrightYear int) {
-	if copyrightYear != 0 {
-		fmt.Fprintf(w, copyrightHeader, copyrightYear)
-	}
+func writeHeader(w io.Writer, tool, pkg string) {
+	fmt.Fprint(w, copyrightHeader)
 	fmt.Fprintf(w, genAndPackageHeader, tool, pkg)
 }
 
 // WritePackageFile adds a file with the provided imports and contents to package.
 // The tool param is used to identify the tool that generated package file.
-func WritePackageFile(tool string, pkg *packages.Package, path string, copyrightYear int, it *ImportTracker, contents *bytes.Buffer) error {
+func WritePackageFile(tool string, pkg *packages.Package, path string, it *ImportTracker, contents *bytes.Buffer) error {
 	buf := new(bytes.Buffer)
-	writeHeader(buf, tool, pkg.Name, copyrightYear)
+	writeHeader(buf, tool, pkg.Name)
 	it.Write(buf)
 	if _, err := buf.Write(contents.Bytes()); err != nil {
 		return err
@@ -271,51 +263,3 @@ func IsViewType(typ types.Type) bool {
 	}
 	return t.Field(0).Name() == "ж"
 }
-
-// CopyrightYear reports the greatest copyright year in non-generated *.go files
-// in the current directory, for use in the copyright line of generated code.
-//
-// It panics on I/O error, as it's assumed this is only being used by "go
-// generate" or GitHub actions.
-//
-// TODO(bradfitz,dgentry): determine what heuristic to use for all this: latest
-// year, earliest, none? don't list years at all? IANAL. Get advice of others.
-// For now we just want to unbreak the tree. See Issue 6865.
-func CopyrightYear(dir string) (year int) {
-	files, err := os.ReadDir(dir)
-	if err != nil {
-		panic(err)
-	}
-	rxYear := regexp.MustCompile(`^// Copyright \(c\) (20\d{2}) `)
-	rxGenerated := regexp.MustCompile(`^// Code generated .* DO NOT EDIT\.$`)
-Files:
-	for _, f := range files {
-		name := f.Name()
-		if !f.Type().IsRegular() ||
-			strings.HasPrefix(name, ".") || // includes emacs noise
-			!strings.HasSuffix(name, ".go") ||
-			strings.HasSuffix(name, "_clone.go") ||
-			strings.HasSuffix(name, "_view.go") ||
-			strings.HasSuffix(name, "_test.go") {
-			continue
-		}
-		src, err := os.ReadFile(filepath.Join(dir, name))
-		if err != nil {
-			panic(err)
-		}
-		bs := bufio.NewScanner(bytes.NewReader(src))
-		for bs.Scan() {
-			line := bs.Bytes()
-			if m := rxYear.FindSubmatch(line); m != nil {
-				if y := must.Get(strconv.Atoi(string(m[1]))); y > year {
-					year = y
-				}
-				continue
-			}
-			if rxGenerated.Match(line) {
-				continue Files
-			}
-		}
-	}
-	return year
-}
diff --git a/wgengine/magicsock/magicsock.go b/wgengine/magicsock/magicsock.go
index 5fb428f71..da756150a 100644
--- a/wgengine/magicsock/magicsock.go
+++ b/wgengine/magicsock/magicsock.go
@@ -4061,7 +4061,7 @@ func (de *endpoint) sendDiscoPing(ep netip.AddrPort, discoKey key.DiscoPublic, t
 // discoPingPurpose is the reason why a discovery ping message was sent.
 type discoPingPurpose int
 
-//go:generate go run tailscale.com/cmd/addlicense -year 2020 -file discopingpurpose_string.go go run golang.org/x/tools/cmd/stringer -type=discoPingPurpose -trimprefix=ping
+//go:generate go run tailscale.com/cmd/addlicense -file discopingpurpose_string.go go run golang.org/x/tools/cmd/stringer -type=discoPingPurpose -trimprefix=ping
 const (
 	// pingDiscovery means that purpose of a ping was to see if a
 	// path was valid.