diff --git a/src/cmd/api/main_test.go b/src/cmd/api/main_test.go
index b071ef5f99..10dbabb9b8 100644
--- a/src/cmd/api/main_test.go
+++ b/src/cmd/api/main_test.go
@@ -1019,7 +1019,7 @@ func (w *Walker) emitType(obj *types.TypeName) {
 
 func (w *Walker) emitStructType(name string, typ *types.Struct) {
 	typeStruct := fmt.Sprintf("type %s struct", name)
-	w.emitf(typeStruct)
+	w.emitf("%s", typeStruct)
 	defer w.pushScope(typeStruct)()
 
 	for i := 0; i < typ.NumFields(); i++ {
diff --git a/src/cmd/asm/internal/asm/parse.go b/src/cmd/asm/internal/asm/parse.go
index 7a52e54090..257311fed9 100644
--- a/src/cmd/asm/internal/asm/parse.go
+++ b/src/cmd/asm/internal/asm/parse.go
@@ -708,7 +708,7 @@ func (p *Parser) registerShift(name string, prefix rune) int64 {
 	if p.arch.Family == sys.ARM64 {
 		off, err := arch.ARM64RegisterShift(r1, op, count)
 		if err != nil {
-			p.errorf(err.Error())
+			p.errorf("%v", err)
 		}
 		return off
 	} else {
@@ -770,7 +770,7 @@ func (p *Parser) registerExtension(a *obj.Addr, name string, prefix rune) {
 	case sys.ARM64:
 		err := arch.ARM64RegisterExtension(a, ext, reg, num, isAmount, isIndex)
 		if err != nil {
-			p.errorf(err.Error())
+			p.errorf("%v", err)
 		}
 	default:
 		p.errorf("register extension not supported on this architecture")
@@ -1117,7 +1117,7 @@ ListLoop:
 			ext := tok.String()
 			curArrangement, err := arch.ARM64RegisterArrangement(reg, name, ext)
 			if err != nil {
-				p.errorf(err.Error())
+				p.errorf("%v", err)
 			}
 			if firstReg == -1 {
 				// only record the first register and arrangement
@@ -1164,7 +1164,7 @@ ListLoop:
 	case sys.ARM64:
 		offset, err := arch.ARM64RegisterListOffset(firstReg, regCnt, arrangement)
 		if err != nil {
-			p.errorf(err.Error())
+			p.errorf("%v", err)
 		}
 		a.Offset = offset
 	default:
diff --git a/src/cmd/cgo/internal/testerrors/argposition_test.go b/src/cmd/cgo/internal/testerrors/argposition_test.go
index b39cc3b3c8..714f9b45f8 100644
--- a/src/cmd/cgo/internal/testerrors/argposition_test.go
+++ b/src/cmd/cgo/internal/testerrors/argposition_test.go
@@ -58,7 +58,7 @@ func (v *Visitor) Visit(node ast.Node) ast.Visitor {
 			}
 
 			if !gotMatch {
-				v.t.Errorf(errorMessage.String())
+				v.t.Error(errorMessage.String())
 			}
 		}
 	}
diff --git a/src/cmd/compile/internal/inline/inlheur/callsite.go b/src/cmd/compile/internal/inline/inlheur/callsite.go
index f457dd439b..abe19cfdd2 100644
--- a/src/cmd/compile/internal/inline/inlheur/callsite.go
+++ b/src/cmd/compile/internal/inline/inlheur/callsite.go
@@ -100,7 +100,7 @@ func fmtFullPos(p src.XPos) string {
 	var sb strings.Builder
 	sep := ""
 	base.Ctxt.AllPos(p, func(pos src.Pos) {
-		fmt.Fprintf(&sb, sep)
+		sb.WriteString(sep)
 		sep = "|"
 		file := filepath.Base(pos.Filename())
 		fmt.Fprintf(&sb, "%s:%d:%d", file, pos.Line(), pos.Col())
diff --git a/src/cmd/compile/internal/ir/reassign_consistency_check.go b/src/cmd/compile/internal/ir/reassign_consistency_check.go
index 06a6c88962..24bbfdfd44 100644
--- a/src/cmd/compile/internal/ir/reassign_consistency_check.go
+++ b/src/cmd/compile/internal/ir/reassign_consistency_check.go
@@ -37,7 +37,7 @@ func fmtFullPos(p src.XPos) string {
 	var sb strings.Builder
 	sep := ""
 	base.Ctxt.AllPos(p, func(pos src.Pos) {
-		fmt.Fprintf(&sb, sep)
+		sb.WriteString(sep)
 		sep = "|"
 		file := filepath.Base(pos.Filename())
 		fmt.Fprintf(&sb, "%s:%d:%d", file, pos.Line(), pos.Col())
diff --git a/src/cmd/compile/internal/liveness/mergelocals.go b/src/cmd/compile/internal/liveness/mergelocals.go
index 25c2c4b3d6..d0675128b8 100644
--- a/src/cmd/compile/internal/liveness/mergelocals.go
+++ b/src/cmd/compile/internal/liveness/mergelocals.go
@@ -1003,7 +1003,7 @@ func fmtFullPos(p src.XPos) string {
 	var sb strings.Builder
 	sep := ""
 	base.Ctxt.AllPos(p, func(pos src.Pos) {
-		fmt.Fprintf(&sb, sep)
+		sb.WriteString(sep)
 		sep = "|"
 		file := filepath.Base(pos.Filename())
 		fmt.Fprintf(&sb, "%s:%d:%d", file, pos.Line(), pos.Col())
diff --git a/src/cmd/compile/internal/liveness/plive.go b/src/cmd/compile/internal/liveness/plive.go
index 6d6b126e4b..a38ea776f9 100644
--- a/src/cmd/compile/internal/liveness/plive.go
+++ b/src/cmd/compile/internal/liveness/plive.go
@@ -1148,7 +1148,7 @@ func (lv *liveness) showlive(v *ssa.Value, live bitvec.BitVec) {
 		s += " " + v
 	}
 
-	base.WarnfAt(pos, s)
+	base.WarnfAt(pos, "%s", s)
 }
 
 func (lv *liveness) printbvec(printed bool, name string, live bitvec.BitVec) bool {
diff --git a/src/cmd/compile/internal/logopt/log_opts.go b/src/cmd/compile/internal/logopt/log_opts.go
index b731e55938..3e7d86aac5 100644
--- a/src/cmd/compile/internal/logopt/log_opts.go
+++ b/src/cmd/compile/internal/logopt/log_opts.go
@@ -309,7 +309,7 @@ func parseLogPath(destination string) (string, string) {
 func checkLogPath(destination string) string {
 	path, complaint := parseLogPath(destination)
 	if complaint != "" {
-		log.Fatalf(complaint)
+		log.Fatal(complaint)
 	}
 	err := os.MkdirAll(path, 0755)
 	if err != nil {
diff --git a/src/cmd/compile/internal/loopvar/loopvar_test.go b/src/cmd/compile/internal/loopvar/loopvar_test.go
index 64cfdb77d9..b19962f0fd 100644
--- a/src/cmd/compile/internal/loopvar/loopvar_test.go
+++ b/src/cmd/compile/internal/loopvar/loopvar_test.go
@@ -141,10 +141,10 @@ func TestLoopVarInlinesGo1_21(t *testing.T) {
 	c := f(root + "/c")
 	m := f(root)
 
-	t.Logf(a)
-	t.Logf(b)
-	t.Logf(c)
-	t.Logf(m)
+	t.Log(a)
+	t.Log(b)
+	t.Log(c)
+	t.Log(m)
 
 	if !strings.Contains(a, "f, af, bf, abf, cf sums = 100, 45, 100, 100, 100") {
 		t.Errorf("Did not see expected value of a")
@@ -200,7 +200,7 @@ func TestLoopVarHashes(t *testing.T) {
 
 	for _, arg := range []string{"v001100110110110010100100", "vx336ca4"} {
 		m := f(arg)
-		t.Logf(m)
+		t.Log(m)
 
 		mCount := countMatches(m, "loopvarhash triggered cmd/compile/internal/loopvar/testdata/inlines/main.go:27:6: .* 001100110110110010100100")
 		otherCount := strings.Count(m, "loopvarhash")
@@ -249,7 +249,7 @@ func TestLoopVarVersionEnableFlag(t *testing.T) {
 	b, err := cmd.CombinedOutput()
 	m := string(b)
 
-	t.Logf(m)
+	t.Log(m)
 
 	yCount := strings.Count(m, "opt.go:16:6: loop variable private now per-iteration, heap-allocated (loop inlined into ./opt.go:29)")
 	nCount := strings.Count(m, "shared")
@@ -288,7 +288,7 @@ func TestLoopVarVersionEnableGoBuild(t *testing.T) {
 	b, err := cmd.CombinedOutput()
 	m := string(b)
 
-	t.Logf(m)
+	t.Log(m)
 
 	yCount := strings.Count(m, "opt-122.go:18:6: loop variable private now per-iteration, heap-allocated (loop inlined into ./opt-122.go:31)")
 	nCount := strings.Count(m, "shared")
@@ -327,7 +327,7 @@ func TestLoopVarVersionDisableFlag(t *testing.T) {
 	b, err := cmd.CombinedOutput()
 	m := string(b)
 
-	t.Logf(m) // expect error
+	t.Log(m) // expect error
 
 	yCount := strings.Count(m, "opt.go:16:6: loop variable private now per-iteration, heap-allocated (loop inlined into ./opt.go:29)")
 	nCount := strings.Count(m, "shared")
@@ -366,7 +366,7 @@ func TestLoopVarVersionDisableGoBuild(t *testing.T) {
 	b, err := cmd.CombinedOutput()
 	m := string(b)
 
-	t.Logf(m) // expect error
+	t.Log(m) // expect error
 
 	yCount := strings.Count(m, "opt-121.go:18:6: loop variable private now per-iteration, heap-allocated (loop inlined into ./opt-121.go:31)")
 	nCount := strings.Count(m, "shared")
diff --git a/src/cmd/compile/internal/ssa/lca_test.go b/src/cmd/compile/internal/ssa/lca_test.go
index 8c8920c740..423627de18 100644
--- a/src/cmd/compile/internal/ssa/lca_test.go
+++ b/src/cmd/compile/internal/ssa/lca_test.go
@@ -11,7 +11,7 @@ func testLCAgen(t *testing.T, bg blockGen, size int) {
 	fun := c.Fun("entry", bg(size)...)
 	CheckFunc(fun.f)
 	if size == 4 {
-		t.Logf(fun.f.String())
+		t.Log(fun.f.String())
 	}
 	lca1 := makeLCArange(fun.f)
 	lca2 := makeLCAeasy(fun.f)
diff --git a/src/cmd/compile/internal/syntax/branches.go b/src/cmd/compile/internal/syntax/branches.go
index 3d7ffed374..8b360176e8 100644
--- a/src/cmd/compile/internal/syntax/branches.go
+++ b/src/cmd/compile/internal/syntax/branches.go
@@ -29,9 +29,9 @@ func checkBranches(body *BlockStmt, errh ErrorHandler) {
 		name := fwd.Label.Value
 		if l := ls.labels[name]; l != nil {
 			l.used = true // avoid "defined and not used" error
-			ls.err(fwd.Label.Pos(), "goto %s jumps into block starting at %s", name, l.parent.start)
+			ls.errf(fwd.Label.Pos(), "goto %s jumps into block starting at %s", name, l.parent.start)
 		} else {
-			ls.err(fwd.Label.Pos(), "label %s not defined", name)
+			ls.errf(fwd.Label.Pos(), "label %s not defined", name)
 		}
 	}
 
@@ -39,7 +39,7 @@ func checkBranches(body *BlockStmt, errh ErrorHandler) {
 	for _, l := range ls.labels {
 		if !l.used {
 			l := l.lstmt.Label
-			ls.err(l.Pos(), "label %s defined and not used", l.Value)
+			ls.errf(l.Pos(), "label %s defined and not used", l.Value)
 		}
 	}
 }
@@ -61,7 +61,7 @@ type block struct {
 	lstmt  *LabeledStmt // labeled statement associated with this block, or nil
 }
 
-func (ls *labelScope) err(pos Pos, format string, args ...interface{}) {
+func (ls *labelScope) errf(pos Pos, format string, args ...interface{}) {
 	ls.errh(Error{pos, fmt.Sprintf(format, args...)})
 }
 
@@ -75,7 +75,7 @@ func (ls *labelScope) declare(b *block, s *LabeledStmt) *label {
 		labels = make(map[string]*label)
 		ls.labels = labels
 	} else if alt := labels[name]; alt != nil {
-		ls.err(s.Label.Pos(), "label %s already defined at %s", name, alt.lstmt.Label.Pos().String())
+		ls.errf(s.Label.Pos(), "label %s already defined at %s", name, alt.lstmt.Label.Pos().String())
 		return alt
 	}
 	l := &label{b, s, false}
@@ -188,7 +188,7 @@ func (ls *labelScope) blockBranches(parent *block, ctxt targets, lstmt *LabeledS
 						fwd.Target = s
 						l.used = true
 						if jumpsOverVarDecl(fwd) {
-							ls.err(
+							ls.errf(
 								fwd.Label.Pos(),
 								"goto %s jumps over declaration of %s at %s",
 								name, String(varName), varPos,
@@ -215,13 +215,13 @@ func (ls *labelScope) blockBranches(parent *block, ctxt targets, lstmt *LabeledS
 					if t := ctxt.breaks; t != nil {
 						s.Target = t
 					} else {
-						ls.err(s.Pos(), "break is not in a loop, switch, or select")
+						ls.errf(s.Pos(), "break is not in a loop, switch, or select")
 					}
 				case _Continue:
 					if t := ctxt.continues; t != nil {
 						s.Target = t
 					} else {
-						ls.err(s.Pos(), "continue is not in a loop")
+						ls.errf(s.Pos(), "continue is not in a loop")
 					}
 				case _Fallthrough:
 					msg := "fallthrough statement out of place"
@@ -237,7 +237,7 @@ func (ls *labelScope) blockBranches(parent *block, ctxt targets, lstmt *LabeledS
 							break // fallthrough ok
 						}
 					}
-					ls.err(s.Pos(), msg)
+					ls.errf(s.Pos(), "%s", msg)
 				case _Goto:
 					fallthrough // should always have a label
 				default:
@@ -258,10 +258,10 @@ func (ls *labelScope) blockBranches(parent *block, ctxt targets, lstmt *LabeledS
 					case *SwitchStmt, *SelectStmt, *ForStmt:
 						s.Target = t
 					default:
-						ls.err(s.Label.Pos(), "invalid break label %s", name)
+						ls.errf(s.Label.Pos(), "invalid break label %s", name)
 					}
 				} else {
-					ls.err(s.Label.Pos(), "break label not defined: %s", name)
+					ls.errf(s.Label.Pos(), "break label not defined: %s", name)
 				}
 
 			case _Continue:
@@ -271,10 +271,10 @@ func (ls *labelScope) blockBranches(parent *block, ctxt targets, lstmt *LabeledS
 					if t, ok := t.Stmt.(*ForStmt); ok {
 						s.Target = t
 					} else {
-						ls.err(s.Label.Pos(), "invalid continue label %s", name)
+						ls.errf(s.Label.Pos(), "invalid continue label %s", name)
 					}
 				} else {
-					ls.err(s.Label.Pos(), "continue label not defined: %s", name)
+					ls.errf(s.Label.Pos(), "continue label not defined: %s", name)
 				}
 
 			case _Goto:
diff --git a/src/cmd/compile/internal/test/mergelocals_test.go b/src/cmd/compile/internal/test/mergelocals_test.go
index 843044d084..77389fa7b7 100644
--- a/src/cmd/compile/internal/test/mergelocals_test.go
+++ b/src/cmd/compile/internal/test/mergelocals_test.go
@@ -161,7 +161,7 @@ func TestMergeLocalsIntegration(t *testing.T) {
 		fields := strings.Fields(line)
 		wantFields := 9
 		if len(fields) != wantFields {
-			t.Logf(string(out))
+			t.Log(string(out))
 			t.Fatalf("bad trace output line, wanted %d fields got %d: %s",
 				wantFields, len(fields), line)
 		}
@@ -173,7 +173,7 @@ func TestMergeLocalsIntegration(t *testing.T) {
 	wantvnum := 8
 	gotvnum := len(vars)
 	if wantvnum != gotvnum {
-		t.Logf(string(out))
+		t.Log(string(out))
 		t.Fatalf("expected trace output on %d vars got %d\n", wantvnum, gotvnum)
 	}
 
diff --git a/src/cmd/compile/internal/test/ssa_test.go b/src/cmd/compile/internal/test/ssa_test.go
index 7f2faa1140..7d213fceca 100644
--- a/src/cmd/compile/internal/test/ssa_test.go
+++ b/src/cmd/compile/internal/test/ssa_test.go
@@ -36,7 +36,7 @@ func runGenTest(t *testing.T, filename, tmpname string, ev ...string) {
 	rungo := filepath.Join(t.TempDir(), "run.go")
 	ok := os.WriteFile(rungo, stdout.Bytes(), 0600)
 	if ok != nil {
-		t.Fatalf("Failed to create temporary file " + rungo)
+		t.Fatalf("Failed to create temporary file %s", rungo)
 	}
 
 	stdout.Reset()
diff --git a/src/cmd/compile/internal/test/testdata/addressed_test.go b/src/cmd/compile/internal/test/testdata/addressed_test.go
index 4cc9ac4d5b..3d315c3a55 100644
--- a/src/cmd/compile/internal/test/testdata/addressed_test.go
+++ b/src/cmd/compile/internal/test/testdata/addressed_test.go
@@ -12,7 +12,7 @@ import (
 var output string
 
 func mypanic(t *testing.T, s string) {
-	t.Fatalf(s + "\n" + output)
+	t.Fatal(s + "\n" + output)
 
 }
 
diff --git a/src/cmd/go/internal/load/pkg.go b/src/cmd/go/internal/load/pkg.go
index 433e951388..17bba88f79 100644
--- a/src/cmd/go/internal/load/pkg.go
+++ b/src/cmd/go/internal/load/pkg.go
@@ -1507,7 +1507,7 @@ func disallowInternal(ctx context.Context, srcDir string, importer *Package, imp
 	perr := &PackageError{
 		alwaysPrintStack: true,
 		ImportStack:      stk.Copy(),
-		Err:              ImportErrorf(p.ImportPath, "use of internal package "+p.ImportPath+" not allowed"),
+		Err:              ImportErrorf(p.ImportPath, "use of internal package %s not allowed", p.ImportPath),
 	}
 	return perr
 }
diff --git a/src/cmd/go/internal/modload/init.go b/src/cmd/go/internal/modload/init.go
index d1e9feab13..69b47ba27f 100644
--- a/src/cmd/go/internal/modload/init.go
+++ b/src/cmd/go/internal/modload/init.go
@@ -1504,7 +1504,7 @@ func setDefaultBuildMod() {
 					}
 				}
 			} else {
-				cfg.BuildModReason = fmt.Sprintf("Go version in " + versionSource + " is unspecified, so vendor directory was not used.")
+				cfg.BuildModReason = fmt.Sprintf("Go version in %s is unspecified, so vendor directory was not used.", versionSource)
 			}
 		}
 	}
diff --git a/src/cmd/internal/goobj/objfile_test.go b/src/cmd/internal/goobj/objfile_test.go
index 10e0564a59..f264aefa9c 100644
--- a/src/cmd/internal/goobj/objfile_test.go
+++ b/src/cmd/internal/goobj/objfile_test.go
@@ -104,11 +104,11 @@ func TestIssue41621LargeNumberOfRelocations(t *testing.T) {
 
 	// Emit testcase.
 	var w bytes.Buffer
-	fmt.Fprintf(&w, issue41621prolog)
+	w.WriteString(issue41621prolog)
 	for i := 0; i < 1048576+13; i++ {
 		fmt.Fprintf(&w, "\t\"%d\",\n", i)
 	}
-	fmt.Fprintf(&w, issue41621epilog)
+	w.WriteString(issue41621epilog)
 	err = os.WriteFile(tmpdir+"/large.go", w.Bytes(), 0666)
 	if err != nil {
 		t.Fatalf("can't write output: %v\n", err)
diff --git a/src/cmd/internal/objabi/flag.go b/src/cmd/internal/objabi/flag.go
index ee7d2fed49..b07a426612 100644
--- a/src/cmd/internal/objabi/flag.go
+++ b/src/cmd/internal/objabi/flag.go
@@ -354,7 +354,7 @@ func (f *DebugFlag) Set(debugstr string) error {
 			}
 			err := f.debugSSA(phase, flag, val, valstring)
 			if err != "" {
-				log.Fatalf(err)
+				log.Fatal(err)
 			}
 			// Setting this false for -d=ssa/... preserves old behavior
 			// of turning off concurrency for any debug flags.
diff --git a/src/cmd/link/internal/loader/loader_test.go b/src/cmd/link/internal/loader/loader_test.go
index eedcc9876b..541f42b7d1 100644
--- a/src/cmd/link/internal/loader/loader_test.go
+++ b/src/cmd/link/internal/loader/loader_test.go
@@ -355,7 +355,7 @@ func TestAddDataMethods(t *testing.T) {
 		name := fmt.Sprintf("new%d", k+1)
 		mi := ldr.LookupOrCreateSym(name, 0)
 		if mi == 0 {
-			t.Fatalf("LookupOrCreateSym failed for '" + name + "'")
+			t.Fatalf("LookupOrCreateSym failed for %q", name)
 		}
 		mi = tp.addDataFunc(ldr, mi, pmi)
 		if ldr.SymType(mi) != tp.expKind {
diff --git a/src/cmd/link/linkbig_test.go b/src/cmd/link/linkbig_test.go
index 45cb1b3ab6..ae9a38fa7b 100644
--- a/src/cmd/link/linkbig_test.go
+++ b/src/cmd/link/linkbig_test.go
@@ -46,7 +46,7 @@ func TestLargeText(t *testing.T) {
 		testname := fmt.Sprintf("bigfn%d", j)
 		fmt.Fprintf(&w, "TEXT ·%s(SB),$0\n", testname)
 		for i := 0; i < 2200000; i++ {
-			fmt.Fprintf(&w, inst)
+			w.WriteString(inst)
 		}
 		fmt.Fprintf(&w, "\tRET\n")
 		err := os.WriteFile(tmpdir+"/"+testname+".s", w.Bytes(), 0666)