diff --git a/internal/api/api.go b/internal/api/api.go
index fc878cf..69e9472 100644
--- a/internal/api/api.go
+++ b/internal/api/api.go
@@ -85,6 +85,7 @@ func (s *Server) routes() []route {
 		{"POST /api/v1/move", authed, s.move},
 		{"POST /api/v1/folders", authed, s.mkdir},
 		{"POST /api/v1/assets", authed, s.uploadAsset},
+		{"POST /api/v1/assets/import", authed, s.importAsset},
 		{"GET /api/v1/raw/{path...}", authed, s.raw},
 		{"GET /api/v1/trash", authed, s.trashList},
 		{"POST /api/v1/trash/{id}/restore", authed, s.trashRestore},
diff --git a/internal/api/import.go b/internal/api/import.go
new file mode 100644
index 0000000..531037f
--- /dev/null
+++ b/internal/api/import.go
@@ -0,0 +1,229 @@
+package api
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"log/slog"
+	"net"
+	"net/http"
+	"net/netip"
+	"net/url"
+	"syscall"
+	"time"
+
+	"rawmark/internal/vault"
+)
+
+var (
+	errImageAddress = errors.New("图片地址必须是公网 HTTP 或 HTTPS 地址")
+	errImageType    = errors.New("仅支持导入 PNG、JPEG、GIF 和 WebP 图片")
+)
+
+var blockedImageNetworks = []netip.Prefix{
+	netip.MustParsePrefix("0.0.0.0/8"),
+	netip.MustParsePrefix("100.64.0.0/10"),
+	netip.MustParsePrefix("192.0.0.0/24"),
+	netip.MustParsePrefix("192.0.2.0/24"),
+	netip.MustParsePrefix("198.18.0.0/15"),
+	netip.MustParsePrefix("198.51.100.0/24"),
+	netip.MustParsePrefix("203.0.113.0/24"),
+	netip.MustParsePrefix("240.0.0.0/4"),
+	netip.MustParsePrefix("2001::/23"),
+	netip.MustParsePrefix("2001:db8::/32"),
+	netip.MustParsePrefix("2002::/16"),
+	netip.MustParsePrefix("3fff::/20"),
+}
+
+func publicImageIP(ip netip.Addr) bool {
+	ip = ip.Unmap()
+	if !ip.IsGlobalUnicast() || ip.IsPrivate() || ip.IsLoopback() || ip.IsLinkLocalUnicast() {
+		return false
+	}
+	// 不接受 IPv6 地址转换前缀，避免其中嵌入的 IPv4 地址访问内网。
+	if ip.Is6() && !netip.MustParsePrefix("2000::/3").Contains(ip) {
+		return false
+	}
+	for _, prefix := range blockedImageNetworks {
+		if prefix.Contains(ip) {
+			return false
+		}
+	}
+	return true
+}
+
+func checkImageURL(u *url.URL) error {
+	if (u.Scheme != "http" && u.Scheme != "https") || u.Hostname() == "" || u.User != nil {
+		return errImageAddress
+	}
+	return nil
+}
+
+var remoteImageClient = &http.Client{
+	Timeout: 10 * time.Second,
+	Transport: &http.Transport{
+		// 不使用环境代理，确保每个实际连接都经过目标地址校验。
+		DialContext: (&net.Dialer{
+			Timeout: 5 * time.Second,
+			ControlContext: func(_ context.Context, _, address string, _ syscall.RawConn) error {
+				host, _, err := net.SplitHostPort(address)
+				if err != nil {
+					return err
+				}
+				ip, err := netip.ParseAddr(host)
+				if err != nil || !publicImageIP(ip) {
+					return errImageAddress
+				}
+				local, err := net.InterfaceAddrs()
+				if err != nil {
+					return err
+				}
+				for _, addr := range local {
+					prefix, err := netip.ParsePrefix(addr.String())
+					if err != nil {
+						return err
+					}
+					if ip.Unmap() == prefix.Addr().Unmap() {
+						return errImageAddress
+					}
+				}
+				return nil
+			},
+		}).DialContext,
+		TLSHandshakeTimeout: 5 * time.Second,
+		IdleConnTimeout:     30 * time.Second,
+		ForceAttemptHTTP2:   true,
+	},
+	CheckRedirect: func(r *http.Request, via []*http.Request) error {
+		if len(via) >= 5 {
+			return errors.New("图片来源重定向次数过多")
+		}
+		r.Header.Del("Referer")
+		return checkImageURL(r.URL)
+	},
+}
+
+// readImageDownload 按实际文件签名确定类型，不信任来源的扩展名或 Content-Type。
+func readImageDownload(body io.Reader) ([]byte, string, error) {
+	data, err := io.ReadAll(io.LimitReader(body, maxAssetBytes+1))
+	if err != nil {
+		return nil, "", err
+	}
+	if int64(len(data)) > maxAssetBytes {
+		return nil, "", vault.ErrTooLarge
+	}
+	var ext string
+	switch http.DetectContentType(data) {
+	case "image/png":
+		ext = ".png"
+	case "image/jpeg":
+		ext = ".jpg"
+	case "image/gif":
+		ext = ".gif"
+	case "image/webp":
+		ext = ".webp"
+	default:
+		return nil, "", errImageType
+	}
+	return data, ext, nil
+}
+
+func (s *Server) importAsset(w http.ResponseWriter, r *http.Request) {
+	var body struct{ URL string }
+	if !readJSON(w, r, &body) {
+		return
+	}
+	u, err := url.Parse(body.URL)
+	if err != nil || checkImageURL(u) != nil {
+		writeError(w, 400, errImageAddress.Error())
+		return
+	}
+	note := r.URL.Query().Get("note")
+	if !vault.IsNote(note) {
+		writeError(w, 400, "所属笔记路径无效")
+		return
+	}
+	if _, err := s.vault.Stat(note); err != nil {
+		vaultError(w, r, err)
+		return
+	}
+	for attempt := 0; attempt < 2; attempt++ {
+		if attempt > 0 {
+			timer := time.NewTimer(time.Second)
+			select {
+			case <-r.Context().Done():
+				timer.Stop()
+				return
+			case <-timer.C:
+			}
+		}
+		req, err := http.NewRequestWithContext(r.Context(), http.MethodGet, u.String(), nil)
+		if err != nil {
+			writeError(w, 400, errImageAddress.Error())
+			return
+		}
+		res, err := remoteImageClient.Do(req)
+		if err != nil {
+			var timeout net.Error
+			if attempt == 0 && errors.As(err, &timeout) && timeout.Timeout() && r.Context().Err() == nil {
+				continue
+			}
+			if errors.Is(err, errImageAddress) {
+				writeError(w, 400, errImageAddress.Error())
+				return
+			}
+			// url.Error 含完整来源 URL，其中可能有临时签名，日志只保留底层原因。
+			var urlError *url.Error
+			if errors.As(err, &urlError) {
+				err = urlError.Err
+			}
+			slog.Error("下载图片失败", "err", err)
+			writeError(w, 502, "下载图片失败")
+			return
+		}
+		if res.StatusCode < 200 || res.StatusCode >= 300 {
+			res.Body.Close()
+			if attempt == 0 && (res.StatusCode == 429 || res.StatusCode >= 500 && res.StatusCode < 600) {
+				continue
+			}
+			writeError(w, 502, fmt.Sprintf("图片来源返回 HTTP %d", res.StatusCode))
+			return
+		}
+		data, ext, err := readImageDownload(res.Body)
+		res.Body.Close()
+		if err != nil {
+			var timeout net.Error
+			if attempt == 0 && errors.As(err, &timeout) && timeout.Timeout() && r.Context().Err() == nil {
+				continue
+			}
+			if errors.Is(err, vault.ErrTooLarge) {
+				vaultError(w, r, err)
+			} else if errors.Is(err, errImageType) {
+				writeError(w, 422, err.Error())
+			} else {
+				slog.Error("读取下载图片失败", "err", err)
+				writeError(w, 502, "读取下载图片失败")
+			}
+			return
+		}
+		// 下载期间笔记可能被外部程序移动或删除；不能在旧路径下创建孤立资源。
+		info, err := s.vault.Stat(note)
+		if err != nil {
+			vaultError(w, r, err)
+			return
+		}
+		if info.IsDir() {
+			writeError(w, 400, "所属路径必须是笔记文件")
+			return
+		}
+		link, err := s.vault.SaveAsset(note, "image"+ext, bytes.NewReader(data), maxAssetBytes)
+		if err != nil {
+			vaultError(w, r, err)
+			return
+		}
+		writeJSON(w, 200, map[string]string{"link": link})
+		return
+	}
+}
diff --git a/internal/api/import_test.go b/internal/api/import_test.go
new file mode 100644
index 0000000..606ac56
--- /dev/null
+++ b/internal/api/import_test.go
@@ -0,0 +1,142 @@
+package api
+
+import (
+	"bytes"
+	"context"
+	"encoding/base64"
+	"encoding/json"
+	"errors"
+	"io"
+	"net"
+	"net/http"
+	"net/http/httptest"
+	"net/netip"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"rawmark/internal/vault"
+)
+
+func TestImportImageAddressBoundary(t *testing.T) {
+	for _, address := range []string{"127.0.0.1", "10.0.0.1", "172.16.0.1", "192.168.0.1", "169.254.169.254", "100.100.100.200", "0.1.2.3", "198.18.0.1", "224.0.0.1", "240.0.0.1", "::", "::1", "::ffff:127.0.0.1", "fc00::1", "fe80::1", "64:ff9b::7f00:1", "2002:7f00:1::", "2001::1", "2001:db8::1", "3fff::1"} {
+		if publicImageIP(netip.MustParseAddr(address)) {
+			t.Errorf("不应接受内网或特殊用途地址 %s", address)
+		}
+	}
+	for _, address := range []string{"1.1.1.1", "8.8.8.8", "2606:4700:4700::1111"} {
+		if !publicImageIP(netip.MustParseAddr(address)) {
+			t.Errorf("应接受公网地址 %s", address)
+		}
+	}
+	f := newFixture(t)
+	f.write("n.md", "正文")
+	for _, source := range []string{"file:///etc/passwd", "ftp://example.com/a.png", "https://user:password@example.com/a.png", "http://127.0.0.1/a.png", "http://[::1]/a.png", "http://localhost/a.png"} {
+		body, err := json.Marshal(map[string]string{"url": source})
+		if err != nil {
+			t.Fatal(err)
+		}
+		if code := f.status(f.admin, "POST", "/api/v1/assets/import?note=n.md", string(body), nil); code != 400 {
+			t.Fatalf("应拒绝非公网图片来源，得到 %d", code)
+		}
+	}
+	if code := f.status(newClient(), "POST", "/api/v1/assets/import?note=n.md", `{"url":"https://example.com/a.png"}`, nil); code != 401 {
+		t.Fatalf("未登录不允许下载: %d", code)
+	}
+}
+
+func TestImportImageDownloadAndRedirects(t *testing.T) {
+	png, err := base64.StdEncoding.DecodeString("iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAQAAAC1HAwCAAAAC0lEQVR42mP8/x8AAwMCAO+aT6sAAAAASUVORK5CYII=")
+	if err != nil {
+		t.Fatal(err)
+	}
+	attempts := map[string]int{}
+	var ownerRoot string
+	source := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		attempts[r.URL.Path]++
+		if r.Header.Get("Cookie") != "" || r.Header.Get("Authorization") != "" || r.Header.Get("Referer") != "" {
+			t.Error("下载请求泄露了凭据或来源")
+		}
+		switch r.URL.Path {
+		case "/private":
+			http.Redirect(w, r, "http://127.0.0.1/private.png", http.StatusFound)
+		case "/scheme":
+			http.Redirect(w, r, "file:///etc/passwd", http.StatusFound)
+		case "/redirect":
+			http.Redirect(w, r, "/image", http.StatusFound)
+		case "/loop":
+			http.Redirect(w, r, "/loop", http.StatusFound)
+		case "/retry":
+			if attempts[r.URL.Path] == 1 {
+				w.WriteHeader(503)
+				return
+			}
+			w.Write(png)
+		case "/failed":
+			w.WriteHeader(429)
+		case "/missing":
+			w.WriteHeader(404)
+		case "/renamed":
+			if err := os.Rename(filepath.Join(ownerRoot, "moving.md"), filepath.Join(ownerRoot, "moved.md")); err != nil {
+				t.Error(err)
+			}
+			w.Write(png)
+		case "/html":
+			w.Header().Set("Content-Type", "image/png")
+			io.WriteString(w, "<script>not an image</script>")
+		default:
+			w.Header().Set("Content-Type", "text/plain")
+			w.Write(png)
+		}
+	}))
+	defer source.Close()
+	original := remoteImageClient
+	transport := original.Transport.(*http.Transport).Clone()
+	dial := transport.DialContext
+	transport.DialContext = func(ctx context.Context, network, address string) (net.Conn, error) {
+		// 只把固定的测试来源映射到本地真实 HTTP 服务，其他目标仍走生产地址校验。
+		if address == "images.example:80" {
+			return (&net.Dialer{}).DialContext(ctx, network, source.Listener.Addr().String())
+		}
+		return dial(ctx, network, address)
+	}
+	client := *original
+	client.Transport = transport
+	remoteImageClient = &client
+	t.Cleanup(func() { transport.CloseIdleConnections(); remoteImageClient = original })
+	f := newFixture(t)
+	ownerRoot = f.root
+	f.write("n.md", "正文")
+	for _, route := range []string{"/image", "/redirect", "/retry"} {
+		body := `{"url":"http://images.example` + route + `"}`
+		result := decode[map[string]string](t, f.do(f.admin, "POST", "/api/v1/assets/import?note=n.md", body, nil))
+		data, err := os.ReadFile(filepath.Join(f.root, filepath.FromSlash(result["link"])))
+		if err != nil || !bytes.Equal(data, png) || !strings.HasSuffix(result["link"], ".png") {
+			t.Fatalf("导入内容、类型或路径不符: %v", err)
+		}
+	}
+	for route, expected := range map[string]int{"/private": 400, "/scheme": 400, "/loop": 502, "/html": 422, "/missing": 502, "/failed": 502} {
+		body := `{"url":"http://images.example` + route + `"}`
+		if code := f.status(f.admin, "POST", "/api/v1/assets/import?note=n.md", body, nil); code != expected {
+			t.Errorf("%s 应返回 %d，得到 %d", route, expected, code)
+		}
+	}
+	if attempts["/retry"] != 2 || attempts["/failed"] != 2 || attempts["/missing"] != 1 || attempts["/loop"] != 5 {
+		t.Fatalf("重试或重定向没有遵守上限: %v", attempts)
+	}
+	f.write("moving.md", "正文")
+	if code := f.status(f.admin, "POST", "/api/v1/assets/import?note=moving.md", `{"url":"http://images.example/renamed"}`, nil); code != 404 {
+		t.Fatalf("下载期间移动的笔记不应写入旧路径: %d", code)
+	}
+	if _, err := os.Stat(filepath.Join(f.root, "moving.assets")); !os.IsNotExist(err) {
+		t.Fatalf("不应在旧位置创建资源: %v", err)
+	}
+}
+
+func TestReadImageDownloadSizeLimit(t *testing.T) {
+	_, _, err := readImageDownload(bytes.NewReader(make([]byte, maxAssetBytes+1)))
+	if !errors.Is(err, vault.ErrTooLarge) {
+		t.Fatalf("超限图片应被拒绝: %v", err)
+	}
+}
diff --git a/internal/api/openapi.json b/internal/api/openapi.json
index aeaa556..08719cb 100644
--- a/internal/api/openapi.json
+++ b/internal/api/openapi.json
@@ -790,6 +790,111 @@
         }
       }
     },
+    "/assets/import": {
+      "post": {
+        "summary": "下载公网图片到笔记的 .assets 目录",
+        "tags": [
+          "图片"
+        ],
+        "description": "仅接受公网 HTTP/HTTPS 地址，实际连接及重定向均校验；不携带登录凭据或使用环境代理。重定向链最多 5 个请求、2 次下载尝试，单次超时 10 秒；仅超时、429 和 5xx 重试。支持 PNG/JPEG/GIF/WebP，按文件签名识别，最大 50 MB。",
+        "parameters": [
+          {
+            "name": "note",
+            "in": "query",
+            "required": true,
+            "schema": {
+              "type": "string"
+            }
+          }
+        ],
+        "requestBody": {
+          "required": true,
+          "content": {
+            "application/json": {
+              "schema": {
+                "type": "object",
+                "required": [
+                  "url"
+                ],
+                "properties": {
+                  "url": {
+                    "type": "string",
+                    "format": "uri"
+                  }
+                }
+              }
+            }
+          }
+        },
+        "responses": {
+          "200": {
+            "description": "相对笔记所在目录的图片链接",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "type": "object",
+                  "properties": {
+                    "link": {
+                      "type": "string"
+                    }
+                  }
+                }
+              }
+            }
+          },
+          "400": {
+            "description": "来源地址或笔记路径无效，或目标不是公网",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/Error"
+                }
+              }
+            }
+          },
+          "404": {
+            "description": "所属笔记不存在",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/Error"
+                }
+              }
+            }
+          },
+          "413": {
+            "description": "图片超过 50 MB",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/Error"
+                }
+              }
+            }
+          },
+          "422": {
+            "description": "不支持的图片类型",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/Error"
+                }
+              }
+            }
+          },
+          "502": {
+            "description": "来源请求失败",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/Error"
+                }
+              }
+            }
+          }
+        }
+      }
+    },
     "/raw/{path}": {
       "parameters": [
         {
diff --git a/web/package-lock.json b/web/package-lock.json
index ae80e87..3778a5b 100644
--- a/web/package-lock.json
+++ b/web/package-lock.json
@@ -18,9 +18,11 @@
         "katex": "^0.18.11",
         "mermaid": "^12.2.0",
         "shiki": "^4.5.0",
+        "turndown": "^7.2.4",
         "vue": "^3.5.44"
       },
       "devDependencies": {
+        "@types/turndown": "^5.0.6",
         "@vitejs/plugin-vue": "^6.0.10",
         "commonmark-spec": "^0.31.2",
         "happy-dom": "^21.0.3",
@@ -398,6 +400,12 @@
         "node": ">=22.12.0"
       }
     },
+    "node_modules/@mixmark-io/domino": {
+      "version": "2.2.0",
+      "resolved": "https://registry.npmjs.org/@mixmark-io/domino/-/domino-2.2.0.tgz",
+      "integrity": "sha512-Y28PR25bHXUg88kCV7nivXrP2Nj2RueZ3/l/jdx6J9f8J4nsEGcgX0Qe6lt7Pa+J79+kPiJU3LguR6O/6zrLOw==",
+      "license": "BSD-2-Clause"
+    },
     "node_modules/@oxc-project/types": {
       "version": "0.154.0",
       "resolved": "https://registry.npmjs.org/@oxc-project/types/-/types-0.154.0.tgz",
@@ -1107,6 +1115,13 @@
       "license": "MIT",
       "optional": true
     },
+    "node_modules/@types/turndown": {
+      "version": "5.0.6",
+      "resolved": "https://registry.npmjs.org/@types/turndown/-/turndown-5.0.6.tgz",
+      "integrity": "sha512-ru00MoyeeouE5BX4gRL+6m/BsDfbRayOskWqUvh7CLGW+UXxHQItqALa38kKnOiZPqJrtzJUgAC2+F0rL1S4Pg==",
+      "dev": true,
+      "license": "MIT"
+    },
     "node_modules/@types/unist": {
       "version": "3.0.3",
       "resolved": "https://registry.npmjs.org/@types/unist/-/unist-3.0.3.tgz",
@@ -3099,6 +3114,19 @@
         "node": ">=6.10"
       }
     },
+    "node_modules/turndown": {
+      "version": "7.2.4",
+      "resolved": "https://registry.npmjs.org/turndown/-/turndown-7.2.4.tgz",
+      "integrity": "sha512-I8yFsfRzmzK0WV1pNNOA4A7y4RDfFxPRxb3t+e3ui14qSGOxGtiSP6GjeX+Y6CHb7HYaFj7ECUD7VE5kQMZWGQ==",
+      "license": "MIT",
+      "dependencies": {
+        "@mixmark-io/domino": "^2.2.0"
+      },
+      "engines": {
+        "node": ">=18",
+        "npm": ">=9"
+      }
+    },
     "node_modules/typescript": {
       "version": "6.0.3",
       "resolved": "https://registry.npmjs.org/typescript/-/typescript-6.0.3.tgz",
diff --git a/web/package.json b/web/package.json
index 16b1712..82fcce9 100644
--- a/web/package.json
+++ b/web/package.json
@@ -21,9 +21,11 @@
     "katex": "^0.18.11",
     "mermaid": "^12.2.0",
     "shiki": "^4.5.0",
+    "turndown": "^7.2.4",
     "vue": "^3.5.44"
   },
   "devDependencies": {
+    "@types/turndown": "^5.0.6",
     "@vitejs/plugin-vue": "^6.0.10",
     "commonmark-spec": "^0.31.2",
     "happy-dom": "^21.0.3",
diff --git a/web/src/app/Workspace.vue b/web/src/app/Workspace.vue
index 27c96f6..8afcfae 100644
--- a/web/src/app/Workspace.vue
+++ b/web/src/app/Workspace.vue
@@ -15,7 +15,7 @@ import { noteTitle } from './paths'
 import { SIDEBAR_WIDTH, settings, updateSettings } from './settings'
 import Sidebar from './Sidebar.vue'
 import TabBar from './TabBar.vue'
-import { activeTab, flushAll, startWorkspace, stopWorkspace, toast, ws } from './workspace'
+import { activeTab, flushAll, readyToReload, startWorkspace, stopWorkspace, toast, ws } from './workspace'
 
 const emit = defineEmits<{ logout: [] }>()
 const title = computed(() => (ws.active ? noteTitle(ws.active) : 'RawMark'))
@@ -43,6 +43,10 @@ function startResize(e: PointerEvent) {
 
 async function logout() {
   await flushAll()
+  if (!readyToReload()) {
+    toast('仍有未保存内容或正在处理粘贴、上传与文件操作，请完成后再退出')
+    return
+  }
   try {
     await api.logout()
   } catch {
diff --git a/web/src/app/api.ts b/web/src/app/api.ts
index c4250d9..4c3d72d 100644
--- a/web/src/app/api.ts
+++ b/web/src/app/api.ts
@@ -159,6 +159,9 @@ export const api = {
     return (await json<{ link: string }>(request('POST', '/api/v1/assets?note=' + encodeURIComponent(note), { body: form }))).link
   },
 
+  importImage: async (note: string, url: string): Promise<string> =>
+    (await json<{ link: string }>(request('POST', '/api/v1/assets/import?note=' + encodeURIComponent(note), { json: { url } }))).link,
+
   shares: async (path?: string) =>
     (await json<{ shares: Share[] }>(request('GET', '/api/v1/shares' + (path ? '?path=' + encodeURIComponent(path) : '')))).shares,
   // expiresIn 为有效时长（秒），0 为永久
diff --git a/web/src/app/workspace.test.ts b/web/src/app/workspace.test.ts
index 6ca742a..1de3954 100644
--- a/web/src/app/workspace.test.ts
+++ b/web/src/app/workspace.test.ts
@@ -6,7 +6,7 @@ import { api, ApiError } from './api'
 import { drafts, type Draft } from './drafts'
 import { connectEvents } from './events'
 import { pluginEvents } from '../plugins/registry'
-import { attachView, closeTab, editorStateOf, flush, keepLocalVersion, openNote, startWorkspace, stopWorkspace, ws } from './workspace'
+import { attachView, closeTab, editorStateOf, flush, keepLocalVersion, openNote, startWorkspace, stopWorkspace, storeViewState, ws } from './workspace'
 
 vi.mock('./events', () => ({ connectEvents: vi.fn(() => () => {}) }))
 
@@ -136,6 +136,32 @@ describe('保存与关闭', () => {
     await closeTab('race.md')
   })
 
+  it('网页图片导入期间切换标签，转换内容仍保存到原笔记', async () => {
+    const v = await edit('网页.md')
+    vi.spyOn(drafts, 'put').mockImplementation(async (draft) => draft.path)
+    const contents = new Map<string, string>()
+    vi.spyOn(api, 'writeFile').mockImplementation(async (path, content) => { contents.set(path, content); return 'r2' })
+    let finish!: (link: string) => void
+    vi.spyOn(api, 'importImage').mockImplementation(() => new Promise<string>((resolve) => { finish = resolve }))
+    const data = new DataTransfer()
+    data.setData('text/plain', '网页标题')
+    data.setData('text/html', '<h1>网页标题</h1><img src="https://example.com/a.png">')
+    v.contentDOM.dispatchEvent(new ClipboardEvent('paste', { clipboardData: data, bubbles: true, cancelable: true }))
+    await vi.waitFor(() => expect(finish).toBeTypeOf('function'))
+    expect(await closeTab('网页.md')).toBe(false)
+    await openNote('other.md')
+    storeViewState('网页.md', v.state)
+    v.setState(editorStateOf('other.md')!)
+    finish('网页.assets/hash.png')
+    await vi.waitFor(() => expect(editorStateOf('网页.md')!.doc.toString()).toContain('网页.assets/hash.png'))
+    await flush('网页.md')
+    expect(contents.get('网页.md')).toContain('# 网页标题')
+    expect(contents.get('网页.md')).toContain('网页.assets/hash.png')
+    expect(v.state.doc.toString()).toBe('原文')
+    await closeTab('网页.md')
+    await closeTab('other.md')
+  })
+
   it('切换标签后上传结果仍写回原笔记，上传期间不能关闭', async () => {
     const v = await edit('image.md')
     vi.spyOn(drafts, 'put').mockImplementation(async (draft) => draft.path)
diff --git a/web/src/app/workspace.ts b/web/src/app/workspace.ts
index df9bce2..b00e00d 100644
--- a/web/src/app/workspace.ts
+++ b/web/src/app/workspace.ts
@@ -188,21 +188,23 @@ function buildState(path: string, doc: string): EditorState {
       }),
       pasteImages({
         upload: (file) => api.upload(ref.path, file),
-        replace: (text, replacement) => {
+        importImage: (url) => api.importImage(ref.path, url),
+        update: (change) => {
           const shown = view?.state.facet(notePath) === ref
           const state = shown ? view!.state : editorStates.get(ref.path)
-          if (!state) throw new Error('上传所属笔记的编辑状态不存在')
-          const at = state.doc.toString().indexOf(text)
-          if (at < 0) return // 用户已删除占位
-          const spec = { changes: { from: at, to: at + text.length, insert: replacement } }
+          if (!state) throw new Error('粘贴所属笔记的编辑状态不存在')
+          const spec = change(state)
+          if (!spec) return
           if (shown) view!.dispatch(spec)
           else {
-            editorStates.set(ref.path, state.update(spec).state)
-            scheduleSave(ref.path)
+            const transaction = state.update(spec)
+            editorStates.set(ref.path, transaction.state)
+            if (transaction.docChanged) scheduleSave(ref.path)
           }
         },
-        onError: (err) => toast('图片上传失败：' + errorText(err)),
+        onError: (err) => toast('粘贴或图片导入失败：' + (err instanceof Error ? err.message : errorText(err))),
         onPending: (d) => {
+          if (d === 1 && slot(ref.path).uploads === 0) toast('正在处理粘贴或图片导入…')
           slot(ref.path).uploads += d
         },
       }),
@@ -911,6 +913,9 @@ export async function startWorkspace() {
     if (document.visibilityState === 'hidden') void flushAll(true)
   })
   window.addEventListener('pagehide', () => void flushAll(true))
+  window.addEventListener('beforeunload', (event) => {
+    if (!readyToReload()) event.preventDefault()
+  })
   window.addEventListener('keydown', handleShortcut)
   // 软键盘弹出、编辑区变矮后，让光标保持可见
   trackVisualViewport(() => {
diff --git a/web/src/editor/html-paste.ts b/web/src/editor/html-paste.ts
new file mode 100644
index 0000000..d8e05a9
--- /dev/null
+++ b/web/src/editor/html-paste.ts
@@ -0,0 +1,74 @@
+import TurndownService from 'turndown'
+
+export async function htmlToMarkdown(html: string, importImage: (url: string) => Promise<string>, onError: (error: unknown) => void): Promise<string> {
+  // template 中的外部资源和脚本保持惰性，不让剪贴板 HTML 进入活动页面。
+  const template = document.createElement('template')
+  template.innerHTML = html
+  const fragment = template.content
+  const base = fragment.querySelector('base[href]')?.getAttribute('href')
+  fragment.querySelectorAll('script,style,iframe,object,embed,template,meta,link,base').forEach((node) => node.remove())
+  if (base) {
+    for (const node of fragment.querySelectorAll('a[href],img[src]')) {
+      const attribute = node.tagName === 'A' ? 'href' : 'src'
+      try { node.setAttribute(attribute, new URL(node.getAttribute(attribute)!, base).href) }
+      catch (error) { onError(new Error('来源基址无效，已保留原链接', { cause: error })) }
+    }
+  }
+
+  const images = new Map<string, HTMLImageElement[]>()
+  for (const image of fragment.querySelectorAll('img')) {
+    let src = image.getAttribute('src') ?? ''
+    if (src.startsWith('//')) { src = 'https:' + src; image.setAttribute('src', src) }
+    if (!/^https?:\/\//i.test(src)) continue
+    const group = images.get(src) ?? []
+    group.push(image)
+    images.set(src, group)
+  }
+  const sources = [...images]
+  // 网页常有多张图片；限制并行数量，避免一次粘贴占满浏览器连接和服务端下载内存。
+  for (let offset = 0; offset < sources.length; offset += 3) {
+    await Promise.all(sources.slice(offset, offset + 3).map(async ([src, nodes]) => {
+      try {
+        const link = await importImage(src)
+        for (const node of nodes) node.setAttribute('src', link)
+      } catch (error) { onError(error) }
+    }))
+  }
+
+  const service = new TurndownService({ headingStyle: 'atx', bulletListMarker: '-', codeBlockStyle: 'fenced' })
+  service.addRule('strikethrough', { filter: (node) => ['DEL', 'S', 'STRIKE'].includes(node.tagName), replacement: (content) => '~~' + content + '~~' })
+  service.addRule('table', {
+    filter: 'table',
+    replacement: (_content, node) => {
+      const rows = [...node.querySelectorAll('tr')].filter((row) => row.closest('table') === node).map((row) =>
+        [...row.cells].map((cell) =>
+          service.turndown(cell).replace(/\|/g, '\\|').replace(/\n+/g, ' '),
+        ),
+      )
+      if (!rows.length) return ''
+      const columns = Math.max(...rows.map((row) => row.length))
+      if (!columns) return ''
+      const line = (cells: string[]) => '| ' + Array.from({ length: columns }, (_, index) => cells[index] ?? '').join(' | ') + ' |'
+      return '\n\n' + [line(rows[0]), line(Array(columns).fill('---')), ...rows.slice(1).map(line)].join('\n') + '\n\n'
+    },
+  })
+  // 链接目标用尖括号包裹，避免 URL 中的括号截断 Markdown；不保留可执行协议。
+  service.addRule('link', {
+    filter: 'a',
+    replacement: (content, node) => {
+      const href = node.getAttribute('href') ?? ''
+      return href && !/^[\s\u0000-\u0020]*(?:javascript|vbscript|data|file):/i.test(href.replace(/[\u0000-\u0020]/g, ''))
+        ? '[' + content + '](<' + href.replace(/</g, '%3C').replace(/>/g, '%3E') + '>)' : content
+    },
+  })
+  service.addRule('image', {
+    filter: 'img',
+    replacement: (_content, node) => {
+      const src = node.getAttribute('src') ?? ''
+      const alt = (node.getAttribute('alt') ?? '').replace(/[\[\]\\]/g, '\\$&').replace(/\n/g, ' ')
+      return src && !/^(?:javascript|vbscript|file):/i.test(src.replace(/[\u0000-\u0020]/g, ''))
+        ? '![' + alt + '](<' + src.replace(/</g, '%3C').replace(/>/g, '%3E') + '>)' : alt
+    },
+  })
+  return service.turndown(fragment)
+}
diff --git a/web/src/editor/paste.test.ts b/web/src/editor/paste.test.ts
new file mode 100644
index 0000000..d697a89
--- /dev/null
+++ b/web/src/editor/paste.test.ts
@@ -0,0 +1,114 @@
+// @vitest-environment happy-dom
+import { afterEach, describe, expect, it, vi } from 'vitest'
+import { history, undo } from '@codemirror/commands'
+import { EditorState } from '@codemirror/state'
+import { EditorView } from '@codemirror/view'
+import { htmlToMarkdown } from './html-paste'
+import { pasteImages } from './paste'
+
+let view: EditorView | undefined
+afterEach(() => { view?.destroy(); view = undefined; vi.restoreAllMocks() })
+
+function paste(html: string, text: string) {
+  const data = new DataTransfer()
+  data.setData('text/html', html)
+  data.setData('text/plain', text)
+  view!.contentDOM.dispatchEvent(new ClipboardEvent('paste', { clipboardData: data, bubbles: true, cancelable: true }))
+}
+
+function editor(importImage: (url: string) => Promise<string> = async () => { throw new Error('此用例不下载图片') }) {
+  let pending = 0
+  const errors: unknown[] = []
+  view = new EditorView({ parent: document.body, state: EditorState.create({ doc: '', extensions: [history(), pasteImages({
+    upload: async () => { throw new Error('此用例不上传文件') },
+    importImage,
+    update: (change) => { const spec = change(view!.state); if (spec) view!.dispatch(spec) },
+    onError: (error) => errors.push(error),
+    onPending: (delta) => { pending += delta },
+  })] }) })
+  return { pending: () => pending, errors }
+}
+
+describe('网页粘贴', () => {
+  it('保留标题、列表、链接、代码块、删除线和表格，并移除活动内容', async () => {
+    const result = await htmlToMarkdown('<h2>标题</h2><ul><li>一</li><li><del>二</del></li></ul><a href="https://example.com/a(b)">链接</a><pre><code class="language-js">const x = 1\n</code></pre><table><tr><th>名称</th><th>值</th></tr><tr><td><strong>甲</strong></td><td>a|b</td></tr></table><script>alert(1)</script><style>body{}</style><a href="java&#9;script:alert(1)">危险链接</a>', async () => '', () => {})
+    expect(result).toContain('## 标题')
+    expect(result).toMatch(/-\s+一/)
+    expect(result).toContain('~~二~~')
+    expect(result).toContain('[链接](<https://example.com/a(b)>)')
+    expect(result).toContain('```js\nconst x = 1\n```')
+    expect(result).toContain('| 名称 | 值 |\n| --- | --- |\n| **甲** | a\\|b |')
+    expect(result).not.toContain('alert(1)')
+    expect(result).not.toContain('body{}')
+    expect(result).toContain('危险链接')
+  })
+
+  it('相同来源只下载一次，失败保留原图链接并报告原始原因', async () => {
+    const failure = new Error('来源拒绝下载')
+    const errors: unknown[] = []
+    const urls: string[] = []
+    const result = await htmlToMarkdown('<base href="https://example.com/docs/"><img alt="图" src="../a.png"><img src="//example.com/a.png"><img src="bad.png">', async (url) => {
+      urls.push(url)
+      if (url.endsWith('bad.png')) throw failure
+      return '笔记.assets/hash.png'
+    }, (error) => errors.push(error))
+    expect(urls.sort()).toEqual(['https://example.com/a.png', 'https://example.com/docs/bad.png'])
+    expect(result.match(/笔记.assets\/hash.png/g)).toHaveLength(2)
+    expect(result).toContain('https://example.com/docs/bad.png')
+    expect(errors).toEqual([failure])
+  })
+
+  it('转换期间的新输入保持原样，撤销一次移除转换后的整次粘贴', async () => {
+    const state = editor()
+    paste('<h1>标题</h1>', '标题')
+    view!.dispatch({ changes: { from: 0, insert: '之后输入' }, userEvent: 'input.type' })
+    await vi.waitFor(() => expect(state.pending()).toBe(0))
+    expect(view!.state.doc.toString()).toBe('# 标题之后输入')
+    undo(view!)
+    expect(view!.state.doc.toString()).toBe('之后输入')
+    undo(view!)
+    expect(view!.state.doc.toString()).toBe('')
+    expect(state.errors).toEqual([])
+  })
+
+  it('用户已修改粘贴区域时不覆盖新输入，Shift 粘贴保持纯文本', async () => {
+    const state = editor()
+    view!.dispatch({ changes: { from: 0, insert: '原选区' }, selection: { anchor: 0, head: 3 } })
+    paste('<h1>标题</h1>', '标题')
+    view!.dispatch({ changes: { from: 1, to: 3, insert: '新输入' } })
+    await vi.waitFor(() => expect(state.pending()).toBe(0))
+    expect(view!.state.doc.toString()).toBe('原新输入')
+    view!.contentDOM.dispatchEvent(new KeyboardEvent('keydown', { key: 'V', shiftKey: true, ctrlKey: true, bubbles: true }))
+    paste('<h1>纯文本</h1>', '纯文本')
+    expect(view!.state.doc.toString()).not.toContain('#')
+    expect(view!.state.doc.toString()).toContain('纯文本')
+    expect(state.pending()).toBe(0)
+  })
+
+  it('同一位置连续发起的异步粘贴保持发起顺序', async () => {
+    const state = editor()
+    paste('<b>第一段</b>', '第一段')
+    paste('<b>第二段</b>', '第二段')
+    await vi.waitFor(() => expect(state.pending()).toBe(0))
+    expect(view!.state.doc.toString()).toBe('**第一段****第二段**')
+  })
+
+  it('后发粘贴的图片先完成时仍保持顺序，撤销会取消尚未插入的粘贴', async () => {
+    const downloads = new Map<string, (link: string) => void>()
+    const state = editor((url) => new Promise((resolve) => downloads.set(url, resolve)))
+    paste('<b>第一段</b><img src="https://example.com/1.png">', '第一段')
+    paste('<b>第二段</b><img src="https://example.com/2.png">', '第二段')
+    await vi.waitFor(() => expect(downloads.size).toBe(2))
+    downloads.get('https://example.com/2.png')!('n.assets/2.png')
+    await vi.waitFor(() => expect(view!.state.doc.toString()).toContain('第二段'))
+    downloads.get('https://example.com/1.png')!('n.assets/1.png')
+    await vi.waitFor(() => expect(state.pending()).toBe(0))
+    expect(view!.state.doc.toString().indexOf('第一段')).toBeLessThan(view!.state.doc.toString().indexOf('第二段'))
+    paste('<b>取消的粘贴</b><img src="https://example.com/3.png">', '取消的粘贴')
+    await vi.waitFor(() => expect(downloads.size).toBe(3))
+    undo(view!)
+    downloads.get('https://example.com/3.png')!('n.assets/3.png')
+    await vi.waitFor(() => expect(state.pending()).toBe(0))
+    expect(view!.state.doc.toString()).not.toContain('取消的粘贴')
+  })
+})
diff --git a/web/src/editor/paste.ts b/web/src/editor/paste.ts
index 6f22ec3..9716457 100644
--- a/web/src/editor/paste.ts
+++ b/web/src/editor/paste.ts
@@ -1,11 +1,13 @@
-import { Facet, type Extension } from '@codemirror/state'
+import { isolateHistory } from '@codemirror/commands'
+import { Facet, StateEffect, StateField, type EditorState, type Extension, type TransactionSpec } from '@codemirror/state'
 import { EditorView } from '@codemirror/view'
 
 export interface PasteImagesOptions {
   // 上传文件，返回写入 Markdown 的链接
   upload: (file: File) => Promise<string>
-  // 按笔记身份修改占位，上传结束时该笔记可能已切到后台
-  replace: (text: string, replacement: string) => void
+  importImage: (url: string) => Promise<string>
+  // 按笔记身份更新，异步粘贴或上传结束时该笔记可能已切到后台。
+  update: (change: (state: EditorState) => TransactionSpec | undefined) => void
   onError: (err: unknown) => void
   // 上传开始/结束，供保存队列在上传期间暂缓保存（避免把临时的 blob: 地址写入文件）
   onPending: (delta: 1 | -1) => void
@@ -13,6 +15,63 @@ export interface PasteImagesOptions {
 
 const uploadOptions = Facet.define<PasteImagesOptions, PasteImagesOptions | undefined>({ combine: (v) => v[0] })
 
+const pasteRange = StateEffect.define<{ id: object; from: number; to: number } | { id: object }>()
+const pendingPastes = StateField.define<Map<object, { from: number; to: number }>>({
+  create: () => new Map(),
+  update(value, transaction) {
+    const next = new Map<object, { from: number; to: number }>()
+    let completed: object | undefined
+    for (const effect of transaction.effects) if (effect.is(pasteRange) && !('from' in effect.value)) completed = effect.value.id
+    let afterCompleted = false
+    for (const [id, range] of value) {
+      if (id === completed) { afterCompleted = true; continue }
+      let edited = transaction.isUserEvent('undo')
+      transaction.changes.iterChangedRanges((from, to) => {
+        if (from < range.to && to > range.from || from === to && from > range.from && from < range.to) edited = true
+      })
+      // 用户在等待期间编辑或撤销了粘贴内容，迟到的转换结果不能覆盖输入。
+      // 同一位置连续粘贴时按发起顺序定位，与图片下载完成的先后无关。
+      const association = range.from === range.to ? (afterCompleted ? 1 : -1) : 1
+      if (!edited) next.set(id, { from: transaction.changes.mapPos(range.from, association), to: transaction.changes.mapPos(range.to, range.from === range.to ? association : -1) })
+    }
+    for (const effect of transaction.effects) if (effect.is(pasteRange)) {
+      if ('from' in effect.value) next.set(effect.value.id, { from: effect.value.from, to: effect.value.to })
+      else next.delete(effect.value.id)
+    }
+    return next
+  },
+})
+
+function replaceText(opts: PasteImagesOptions, text: string, replacement: string) {
+  opts.update((state) => {
+    const at = state.doc.toString().indexOf(text)
+    if (at >= 0) return { changes: { from: at, to: at + text.length, insert: replacement } }
+  })
+}
+
+function insertHTML(view: EditorView, html: string, text: string, opts: PasteImagesOptions) {
+  const id = {}
+  const range = view.state.selection.main
+  opts.onPending(1)
+  view.dispatch({ effects: pasteRange.of({ id, from: range.from, to: range.to }) })
+  const insert = (markdown: string) => {
+    opts.update((state) => {
+      const pending = state.field(pendingPastes).get(id)
+      if (pending) return {
+        changes: { from: pending.from, to: pending.to, insert: markdown },
+        selection: state.selection.main.from === pending.from && state.selection.main.to === pending.to ? { anchor: pending.from + markdown.length } : undefined,
+        effects: pasteRange.of({ id }),
+        userEvent: 'input.paste',
+        annotations: isolateHistory.of('full'),
+      }
+    })
+  }
+  void import('./html-paste').then(({ htmlToMarkdown }) => htmlToMarkdown(html, opts.importImage, opts.onError)).catch((error) => {
+    opts.onError(new Error('网页转换失败，已保留剪贴板纯文本', { cause: error }))
+    return text
+  }).then(insert).catch(opts.onError).finally(() => opts.onPending(-1))
+}
+
 /**
  * 插入图片文件（粘贴、拖入、从相册选择共用）：先用 blob: 地址插入占位，立即显示；上传完成后替换为正式链接。
  * 返回是否有图片被插入；编辑器未配置上传（pasteImages）时不处理
@@ -35,9 +94,9 @@ export function insertImageFiles(view: EditorView, files: File[], pos?: number):
     opts.onPending(1)
     opts
       .upload(file)
-      .then((link) => opts.replace(urls[i], link))
+      .then((link) => replaceText(opts, urls[i], link))
       .catch((err) => {
-        opts.replace(`![](${urls[i]})`, '')
+        replaceText(opts, `![](${urls[i]})`, '')
         opts.onError(err)
       })
       .finally(() => {
@@ -50,10 +109,22 @@ export function insertImageFiles(view: EditorView, files: File[], pos?: number):
 
 // 粘贴或拖入图片
 export function pasteImages(opts: PasteImagesOptions): Extension {
+  let plain = false
   return [
     uploadOptions.of(opts),
+    pendingPastes,
     EditorView.domEventHandlers({
+      keydown(e) { plain = e.shiftKey },
+      keyup(e) { plain = e.shiftKey },
+      blur() { plain = false },
       paste(e, view) {
+        if (view.state.readOnly || plain) return false
+        const html = e.clipboardData?.getData('text/html')
+        if (html) {
+          insertHTML(view, html, e.clipboardData!.getData('text/plain'), opts)
+          e.preventDefault()
+          return true
+        }
         // 个别浏览器/来源只在 items 中提供图片
         let files = [...(e.clipboardData?.files ?? [])]
         if (!files.length) {
@@ -64,6 +135,7 @@ export function pasteImages(opts: PasteImagesOptions): Extension {
         return true
       },
       drop(e, view) {
+        if (view.state.readOnly) return false
         const files = [...(e.dataTransfer?.files ?? [])]
         const pos = view.posAtCoords(e)
         if (!files.length || !insertImageFiles(view, files, pos ?? undefined)) return false