diff --git a/json_editor.go b/json_editor.go
new file mode 100644
index 0000000..eb66d78
--- /dev/null
+++ b/json_editor.go
@@ -0,0 +1,146 @@
+package mujica
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"log/slog"
+	"strings"
+
+	"github.com/egoist/mygo/ui"
+
+	"mujicaui/icons"
+	"mujicaui/internal"
+	"mujicaui/theme"
+)
+
+// JsonEditorOptions configure a JsonEditor.
+type JsonEditorOptions struct {
+	// Label names the editor; empty uses "JSON".
+	Label string
+	// MinHeight and MaxHeight bound the text; zero means 160 and 400.
+	MinHeight, MaxHeight float32
+	Disabled             bool
+}
+
+// JsonEditorResult reports this frame's events and the parse state.
+type JsonEditorResult struct {
+	Element *ui.Element
+	Changed bool
+	// Valid reports *text parses as one JSON value.
+	Valid bool
+	// Line and Column locate a parse error, 1-based; 0 when valid.
+	Line, Column int
+}
+
+type jsonEditorCheck struct {
+	src          string
+	err          string
+	line, column int
+}
+
+// JsonEditor edits JSON text, formats it and points at the line and column of a parse error.
+func JsonEditor(c *ui.Context, text *string, opts JsonEditorOptions) JsonEditorResult {
+	if text == nil || opts.MinHeight < 0 || opts.MaxHeight < 0 {
+		panic("mujica: JsonEditor needs text and non-negative heights")
+	}
+	label := opts.Label
+	if label == "" {
+		label = msg(c, "json_editor.label")
+	}
+	minH, maxH := opts.MinHeight, opts.MaxHeight
+	if minH == 0 {
+		minH = 160
+	}
+	if maxH == 0 {
+		maxH = 400
+	}
+	k := Tokens(c)
+	u := Density(c).Unit()
+	var r JsonEditorResult
+	r.Element = ui.Column(c).Shrink(0).Gap(u * 2).Disabled(opts.Disabled)
+	chk := ui.Local(r.Element, "mujica.jsoneditor", func() jsonEditorCheck { return jsonEditorCheck{src: "\x00"} })
+	locked := r.Element.IsDisabled()
+	r.Element.Children(func() {
+		jsonEditorValidate(chk, *text)
+		ui.Row(c).Gap(u * 2).AlignItems(ui.Center).Children(func() {
+			ui.Text(c, label).FontWeight(600).Grow(1)
+			if Button(c, msg(c, "json_editor.format"), ButtonOptions{Variant: Secondary, Disabled: locked || chk.err != ""}).Clicked() && !locked {
+				var b bytes.Buffer
+				if json.Indent(&b, []byte(*text), "", "  ") == nil && b.String() != *text {
+					*text, r.Changed = b.String(), true
+					slog.Debug("mujica: json_editor format")
+				}
+			}
+		})
+		in := TextArea(c, text, TextAreaOptions{Label: label, MinHeight: minH, MaxHeight: maxH, Disabled: locked, Error: chk.err})
+		in.Input.Font(theme.MonoFont).FontSize(FontSize(c, codeSize))
+		r.Changed = r.Changed || in.Changed()
+		jsonEditorValidate(chk, *text)
+		if chk.err != "" {
+			lines := strings.Split(*text, "\n")
+			if chk.line >= 1 && chk.line <= len(lines) {
+				jsonEditorExcerpt(c, lines[chk.line-1], chk.line, chk.column)
+			}
+			return
+		}
+		ui.Row(c).Gap(u).AlignItems(ui.Center).Role(ui.RoleStatus).Children(func() {
+			ui.Icon(c, icons.Must("circle-check")).Size(14, 14).TextColor(k.Success)
+			ui.Text(c, msg(c, "json_editor.valid")).TextColor(k.Success).FontSize(FontSize(c, theme.CaptionSize+1))
+		})
+	})
+	r.Valid, r.Line, r.Column = chk.err == "", chk.line, chk.column
+	return r
+}
+
+// jsonEditorValidate parses text once per change and locates any error.
+func jsonEditorValidate(chk *jsonEditorCheck, text string) {
+	if chk.src == text {
+		return
+	}
+	chk.src, chk.err, chk.line, chk.column = text, "", 0, 0
+	dec := json.NewDecoder(strings.NewReader(text))
+	var v any
+	err := dec.Decode(&v)
+	offset := dec.InputOffset()
+	if err == nil && dec.More() {
+		err = errors.New("unexpected data after the value")
+	}
+	if err == nil {
+		return
+	}
+	var syn *json.SyntaxError
+	var typ *json.UnmarshalTypeError
+	switch {
+	case errors.As(err, &syn):
+		offset = syn.Offset
+	case errors.As(err, &typ):
+		offset = typ.Offset
+	case strings.TrimSpace(text) == "":
+		err, offset = errors.New("empty document"), 0
+	default:
+		offset = int64(len(text))
+	}
+	before := text[:min(int(offset), len(text))]
+	chk.line = strings.Count(before, "\n") + 1
+	chk.column = len([]rune(before[strings.LastIndex(before, "\n")+1:]))
+	chk.column = max(chk.column, 1)
+	chk.err = fmt.Sprintf("%d:%d %v", chk.line, chk.column, err)
+}
+
+// jsonEditorExcerpt shows the error line with a caret under the column.
+func jsonEditorExcerpt(c *ui.Context, line string, n, col int) {
+	k := Tokens(c)
+	u := Density(c).Unit()
+	ui.Column(c).Padding(u*2, u*3).Radius(theme.ControlRadius).Background(k.Background).Border(theme.BorderWidth, k.Border).
+		Label(fmt.Sprintf(msg(c, "json_editor.at"), n, col)).Children(func() {
+		spans := []ui.Span{{Text: fmt.Sprintf("%4d | ", n), Color: k.TextMuted}}
+		toks, _ := internal.Highlight("json", line, false)
+		for _, t := range toks {
+			spans = append(spans, ui.Span{Text: t.Text, Color: codeTokenColor(k, t.Kind)})
+		}
+		ui.RichText(c, spans...).Font(theme.MonoFont).FontSize(FontSize(c, codeSize)).SingleLine()
+		codeMono(c, strings.Repeat(" ", 7+col-1)+"^").TextColor(k.Danger)
+	})
+}
diff --git a/json_editor_test.go b/json_editor_test.go
new file mode 100644
index 0000000..ebed49e
--- /dev/null
+++ b/json_editor_test.go
@@ -0,0 +1,75 @@
+package mujica
+
+import (
+	"testing"
+
+	"github.com/egoist/mygo/ui"
+)
+
+func jsonEditorTester(text *string, opts JsonEditorOptions, last *JsonEditorResult) *ui.Tester {
+	return ui.NewTester(func(c *ui.Context) {
+		Use(c, Settings{})
+		*last = JsonEditor(c, text, opts)
+	}, 600, 460)
+}
+
+func TestJsonEditorFormatAndValid(t *testing.T) {
+	text := `{"hall":"east","guests":[1,2]}`
+	var r JsonEditorResult
+	tt := jsonEditorTester(&text, JsonEditorOptions{}, &r)
+	if !r.Valid || !tt.HasText("Valid JSON") {
+		t.Fatalf("valid: %+v", r)
+	}
+	_ = tt.Click("Format")
+	if text != "{\n  \"hall\": \"east\",\n  \"guests\": [\n    1,\n    2\n  ]\n}" {
+		t.Fatalf("formatted %q", text)
+	}
+}
+
+func TestJsonEditorErrorLocation(t *testing.T) {
+	text := "{\n  \"hall\": \"east\",\n  \"guests\": [1, 2,]\n}"
+	var r JsonEditorResult
+	tt := jsonEditorTester(&text, JsonEditorOptions{}, &r)
+	if r.Valid || r.Line != 3 || r.Column != 19 {
+		t.Fatalf("location %+v", r)
+	}
+	if !tt.HasText("   3 | ") || !tt.HasText("                         ^") {
+		t.Fatalf("excerpt: %q", tt.Texts())
+	}
+	_ = tt.Click("Format") // disabled while invalid
+	if r.Changed {
+		t.Fatal("formatted invalid JSON")
+	}
+	text = "{} {}"
+	tt.Frame()
+	if r.Valid || r.Line != 1 {
+		t.Fatalf("trailing value: %+v", r)
+	}
+}
+
+func TestJsonEditorTypingAndDisabled(t *testing.T) {
+	text := ""
+	var r JsonEditorResult
+	tt := jsonEditorTester(&text, JsonEditorOptions{}, &r)
+	if r.Valid {
+		t.Fatal("empty text is valid")
+	}
+	tt.Key(0, ui.KeyTab) // Format is disabled while invalid
+	tt.Type(`[true]`)
+	if !r.Valid || text != "[true]" {
+		t.Fatalf("typed %q valid %v", text, r.Valid)
+	}
+	tt = jsonEditorTester(&text, JsonEditorOptions{Disabled: true}, &r)
+	tt.Key(0, ui.KeyTab)
+	tt.Type("x")
+	if text != "[true]" {
+		t.Fatalf("disabled edited: %q", text)
+	}
+}
+
+func TestJsonEditorSnapshot(t *testing.T) {
+	snapshot(t, "json_editor", 560, 360, func(c *ui.Context) {
+		text := "{\n  \"hall\": \"east wing\",\n  \"guests\": [1, 2,]\n}"
+		ui.Column(c).Padding(16).Children(func() { JsonEditor(c, &text, JsonEditorOptions{MinHeight: 120}) })
+	})
+}
diff --git a/messages_devtools.go b/messages_devtools.go
index abe4d0e..5a02788 100644
--- a/messages_devtools.go
+++ b/messages_devtools.go
@@ -82,6 +82,11 @@ func init() {
 		"json_viewer.copy":    {"Copy path", "复制路径"},
 		"json_viewer.items":   {"%s %d items %s", "%s %d 项 %s"},
 
+		"json_editor.label":  {"JSON", "JSON"},
+		"json_editor.format": {"Format", "格式化"},
+		"json_editor.valid":  {"Valid JSON", "JSON 有效"},
+		"json_editor.at":     {"Error at line %d, column %d", "错误位于第 %d 行第 %d 列"},
+
 		"alert_list.empty": {"No alerts", "没有告警"},
 	})
 }
diff --git a/testdata/snapshots/darwin/json_editor-dark.png b/testdata/snapshots/darwin/json_editor-dark.png
new file mode 100644
index 0000000..8c843a6
Binary files /dev/null and b/testdata/snapshots/darwin/json_editor-dark.png differ
diff --git a/testdata/snapshots/darwin/json_editor-light.png b/testdata/snapshots/darwin/json_editor-light.png
new file mode 100644
index 0000000..59b92e9
Binary files /dev/null and b/testdata/snapshots/darwin/json_editor-light.png differ