diff --git a/src/display/display_utils.js b/src/display/display_utils.js
index c34035f2c..be4b20c7c 100644
--- a/src/display/display_utils.js
+++ b/src/display/display_utils.js
@@ -13,24 +13,21 @@
  * limitations under the License.
  */
 
-import {
-  assert,
-  BaseException,
-  isString,
-  removeNullCharacters,
-  shadow,
-  stringToBytes,
-  Util,
-  warn,
-} from "../shared/util.js";
 import {
   BaseCanvasFactory,
   BaseCMapReaderFactory,
   BaseStandardFontDataFactory,
   BaseSVGFactory,
 } from "./base_factory.js";
+import {
+  BaseException,
+  isString,
+  shadow,
+  stringToBytes,
+  Util,
+  warn,
+} from "../shared/util.js";
 
-const DEFAULT_LINK_REL = "noopener noreferrer nofollow";
 const SVG_NS = "http://www.w3.org/2000/svg";
 
 const PixelsPerInch = {
@@ -316,70 +313,6 @@ class RenderingCancelledException extends BaseException {
   }
 }
 
-const LinkTarget = {
-  NONE: 0, // Default value.
-  SELF: 1,
-  BLANK: 2,
-  PARENT: 3,
-  TOP: 4,
-};
-
-/**
- * @typedef ExternalLinkParameters
- * @typedef {Object} ExternalLinkParameters
- * @property {string} url - An absolute URL.
- * @property {LinkTarget} [target] - The link target. The default value is
- *   `LinkTarget.NONE`.
- * @property {string} [rel] - The link relationship. The default value is
- *   `DEFAULT_LINK_REL`.
- * @property {boolean} [enabled] - Whether the link should be enabled. The
- *   default value is true.
- */
-
-/**
- * Adds various attributes (href, title, target, rel) to hyperlinks.
- * @param {HTMLAnchorElement} link - The link element.
- * @param {ExternalLinkParameters} params
- */
-function addLinkAttributes(link, { url, target, rel, enabled = true } = {}) {
-  assert(
-    url && typeof url === "string",
-    'addLinkAttributes: A valid "url" parameter must provided.'
-  );
-
-  const urlNullRemoved = removeNullCharacters(url);
-  if (enabled) {
-    link.href = link.title = urlNullRemoved;
-  } else {
-    link.href = "";
-    link.title = `Disabled: ${urlNullRemoved}`;
-    link.onclick = () => {
-      return false;
-    };
-  }
-
-  let targetStr = ""; // LinkTarget.NONE
-  switch (target) {
-    case LinkTarget.NONE:
-      break;
-    case LinkTarget.SELF:
-      targetStr = "_self";
-      break;
-    case LinkTarget.BLANK:
-      targetStr = "_blank";
-      break;
-    case LinkTarget.PARENT:
-      targetStr = "_parent";
-      break;
-    case LinkTarget.TOP:
-      targetStr = "_top";
-      break;
-  }
-  link.target = targetStr;
-
-  link.rel = typeof rel === "string" ? rel : DEFAULT_LINK_REL;
-}
-
 function isDataScheme(url) {
   const ii = url.length;
   let i = 0;
@@ -632,7 +565,6 @@ function getXfaPageViewport(xfaPage, { scale = 1, rotation = 0 }) {
 }
 
 export {
-  addLinkAttributes,
   deprecated,
   DOMCanvasFactory,
   DOMCMapReaderFactory,
@@ -644,7 +576,6 @@ export {
   isDataScheme,
   isPdfFile,
   isValidFetchUrl,
-  LinkTarget,
   loadScript,
   PageViewport,
   PDFDateString,
diff --git a/src/pdf.js b/src/pdf.js
index 3a4b38e0f..d89ac3af8 100644
--- a/src/pdf.js
+++ b/src/pdf.js
@@ -12,7 +12,6 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-/* eslint-disable sort-exports/sort-exports */
 
 // eslint-disable-next-line max-len
 /** @typedef {import("./display/api").PDFDocumentLoadingTask} PDFDocumentLoadingTask */
@@ -20,19 +19,6 @@
 /** @typedef {import("./display/api").PDFPageProxy} PDFPageProxy */
 /** @typedef {import("./display/api").RenderTask} RenderTask */
 
-import {
-  addLinkAttributes,
-  getFilenameFromUrl,
-  getPdfFilenameFromUrl,
-  getXfaPageViewport,
-  isPdfFile,
-  isValidFetchUrl,
-  LinkTarget,
-  loadScript,
-  PDFDateString,
-  PixelsPerInch,
-  RenderingCancelledException,
-} from "./display/display_utils.js";
 import {
   AnnotationMode,
   CMapCompressionType,
@@ -44,7 +30,6 @@ import {
   OPS,
   PasswordResponses,
   PermissionFlag,
-  removeNullCharacters,
   shadow,
   UnexpectedResponseException,
   UNSUPPORTED_FEATURES,
@@ -60,6 +45,17 @@ import {
   setPDFNetworkStreamFactory,
   version,
 } from "./display/api.js";
+import {
+  getFilenameFromUrl,
+  getPdfFilenameFromUrl,
+  getXfaPageViewport,
+  isPdfFile,
+  isValidFetchUrl,
+  loadScript,
+  PDFDateString,
+  PixelsPerInch,
+  RenderingCancelledException,
+} from "./display/display_utils.js";
 import { AnnotationLayer } from "./display/annotation_layer.js";
 import { GlobalWorkerOptions } from "./display/worker_options.js";
 import { isNodeJS } from "./shared/is_node.js";
@@ -108,49 +104,38 @@ if (typeof PDFJSDev === "undefined" || !PDFJSDev.test("PRODUCTION")) {
 }
 
 export {
-  // From "./display/display_utils.js":
-  addLinkAttributes,
-  getFilenameFromUrl,
-  getPdfFilenameFromUrl,
-  isPdfFile,
-  LinkTarget,
-  loadScript,
-  PDFDateString,
-  PixelsPerInch,
-  RenderingCancelledException,
-  getXfaPageViewport,
-  // From "./shared/util.js":
+  AnnotationLayer,
   AnnotationMode,
+  build,
   CMapCompressionType,
   createObjectURL,
   createPromiseCapability,
   createValidAbsoluteUrl,
+  getDocument,
+  getFilenameFromUrl,
+  getPdfFilenameFromUrl,
+  getXfaPageViewport,
+  GlobalWorkerOptions,
   InvalidPDFException,
+  isPdfFile,
+  loadScript,
+  LoopbackPort,
   MissingPDFException,
   OPS,
   PasswordResponses,
+  PDFDataRangeTransport,
+  PDFDateString,
+  PDFWorker,
   PermissionFlag,
-  removeNullCharacters,
+  PixelsPerInch,
+  RenderingCancelledException,
+  renderTextLayer,
   shadow,
+  SVGGraphics,
   UnexpectedResponseException,
   UNSUPPORTED_FEATURES,
   Util,
   VerbosityLevel,
-  // From "./display/api.js":
-  build,
-  getDocument,
-  LoopbackPort,
-  PDFDataRangeTransport,
-  PDFWorker,
   version,
-  // From "./display/annotation_layer.js":
-  AnnotationLayer,
-  // From "./display/worker_options.js":
-  GlobalWorkerOptions,
-  // From "./display/text_layer.js":
-  renderTextLayer,
-  // From "./display/svg.js":
-  SVGGraphics,
-  // From "./display/xfa_layer.js":
   XfaLayer,
 };
diff --git a/src/shared/util.js b/src/shared/util.js
index 7211254dd..214624236 100644
--- a/src/shared/util.js
+++ b/src/shared/util.js
@@ -575,23 +575,6 @@ class AbortException extends BaseException {
   }
 }
 
-const NullCharactersRegExp = /\x00+/g;
-const InvisibleCharactersRegExp = /[\x01-\x1F]/g;
-
-/**
- * @param {string} str
- */
-function removeNullCharacters(str, replaceInvisible = false) {
-  if (typeof str !== "string") {
-    warn("The argument for removeNullCharacters must be a string.");
-    return str;
-  }
-  if (replaceInvisible) {
-    str = str.replace(InvisibleCharactersRegExp, " ");
-  }
-  return str.replace(NullCharactersRegExp, "");
-}
-
 function bytesToString(bytes) {
   assert(
     bytes !== null && typeof bytes === "object" && bytes.length !== undefined,
@@ -1185,7 +1168,6 @@ export {
   PasswordException,
   PasswordResponses,
   PermissionFlag,
-  removeNullCharacters,
   RenderingIntentFlag,
   setVerbosityLevel,
   shadow,
diff --git a/test/unit/ui_utils_spec.js b/test/unit/ui_utils_spec.js
index d262f1079..c83e2f056 100644
--- a/test/unit/ui_utils_spec.js
+++ b/test/unit/ui_utils_spec.js
@@ -21,6 +21,7 @@ import {
   isPortraitOrientation,
   isValidRotation,
   parseQueryString,
+  removeNullCharacters,
 } from "../../web/ui_utils.js";
 
 describe("ui_utils", function () {
@@ -139,6 +140,30 @@ describe("ui_utils", function () {
     });
   });
 
+  describe("removeNullCharacters", function () {
+    it("should not modify string without null characters", function () {
+      const str = "string without null chars";
+      expect(removeNullCharacters(str)).toEqual("string without null chars");
+    });
+
+    it("should modify string with null characters", function () {
+      const str = "string\x00With\x00Null\x00Chars";
+      expect(removeNullCharacters(str)).toEqual("stringWithNullChars");
+    });
+
+    it("should modify string with non-displayable characters", function () {
+      const str = Array.from(Array(32).keys())
+        .map(x => String.fromCharCode(x) + "a")
+        .join("");
+      // \x00 is replaced by an empty string.
+      const expected =
+        "a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a";
+      expect(removeNullCharacters(str, /* replaceInvisible */ true)).toEqual(
+        expected
+      );
+    });
+  });
+
   describe("getPageSizeInches", function () {
     it("gets page size (in inches)", function () {
       const page = {
diff --git a/test/unit/util_spec.js b/test/unit/util_spec.js
index b86d287c4..941e2542c 100644
--- a/test/unit/util_spec.js
+++ b/test/unit/util_spec.js
@@ -25,7 +25,6 @@ import {
   isNum,
   isSameOrigin,
   isString,
-  removeNullCharacters,
   string32,
   stringToBytes,
   stringToPDFString,
@@ -175,30 +174,6 @@ describe("util", function () {
     });
   });
 
-  describe("removeNullCharacters", function () {
-    it("should not modify string without null characters", function () {
-      const str = "string without null chars";
-      expect(removeNullCharacters(str)).toEqual("string without null chars");
-    });
-
-    it("should modify string with null characters", function () {
-      const str = "string\x00With\x00Null\x00Chars";
-      expect(removeNullCharacters(str)).toEqual("stringWithNullChars");
-    });
-
-    it("should modify string with non-displayable characters", function () {
-      const str = Array.from(Array(32).keys())
-        .map(x => String.fromCharCode(x) + "a")
-        .join("");
-      // \x00 is replaced by an empty string.
-      const expected =
-        "a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a a";
-      expect(removeNullCharacters(str, /* replaceInvisible */ true)).toEqual(
-        expected
-      );
-    });
-  });
-
   describe("ReadableStream", function () {
     it("should return an Object", function () {
       const readable = new ReadableStream();
diff --git a/web/app.js b/web/app.js
index 912880dee..2824358d1 100644
--- a/web/app.js
+++ b/web/app.js
@@ -46,7 +46,6 @@ import {
   GlobalWorkerOptions,
   InvalidPDFException,
   isPdfFile,
-  LinkTarget,
   loadScript,
   MissingPDFException,
   OPS,
@@ -57,6 +56,7 @@ import {
   version,
 } from "pdfjs-lib";
 import { CursorTool, PDFCursorTools } from "./pdf_cursor_tools.js";
+import { LinkTarget, PDFLinkService } from "./pdf_link_service.js";
 import { OverlayManager } from "./overlay_manager.js";
 import { PasswordPrompt } from "./password_prompt.js";
 import { PDFAttachmentViewer } from "./pdf_attachment_viewer.js";
@@ -65,7 +65,6 @@ import { PDFFindBar } from "./pdf_find_bar.js";
 import { PDFFindController } from "./pdf_find_controller.js";
 import { PDFHistory } from "./pdf_history.js";
 import { PDFLayerViewer } from "./pdf_layer_viewer.js";
-import { PDFLinkService } from "./pdf_link_service.js";
 import { PDFOutlineViewer } from "./pdf_outline_viewer.js";
 import { PDFPresentationMode } from "./pdf_presentation_mode.js";
 import { PDFRenderingQueue } from "./pdf_rendering_queue.js";
diff --git a/web/base_tree_viewer.js b/web/base_tree_viewer.js
index 7a4f1e030..7a3168128 100644
--- a/web/base_tree_viewer.js
+++ b/web/base_tree_viewer.js
@@ -13,7 +13,7 @@
  * limitations under the License.
  */
 
-import { removeNullCharacters } from "pdfjs-lib";
+import { removeNullCharacters } from "./ui_utils.js";
 
 const TREEITEM_OFFSET_TOP = -100; // px
 const TREEITEM_SELECTED_CLASS = "selected";
diff --git a/web/pdf_link_service.js b/web/pdf_link_service.js
index 3f6e4eb25..6e2a5f989 100644
--- a/web/pdf_link_service.js
+++ b/web/pdf_link_service.js
@@ -16,8 +16,72 @@
 /** @typedef {import("./event_utils").EventBus} EventBus */
 /** @typedef {import("./interfaces").IPDFLinkService} IPDFLinkService */
 
-import { addLinkAttributes, LinkTarget } from "pdfjs-lib";
-import { parseQueryString } from "./ui_utils.js";
+import { parseQueryString, removeNullCharacters } from "./ui_utils.js";
+
+const DEFAULT_LINK_REL = "noopener noreferrer nofollow";
+
+const LinkTarget = {
+  NONE: 0, // Default value.
+  SELF: 1,
+  BLANK: 2,
+  PARENT: 3,
+  TOP: 4,
+};
+
+/**
+ * @typedef ExternalLinkParameters
+ * @typedef {Object} ExternalLinkParameters
+ * @property {string} url - An absolute URL.
+ * @property {LinkTarget} [target] - The link target. The default value is
+ *   `LinkTarget.NONE`.
+ * @property {string} [rel] - The link relationship. The default value is
+ *   `DEFAULT_LINK_REL`.
+ * @property {boolean} [enabled] - Whether the link should be enabled. The
+ *   default value is true.
+ */
+
+/**
+ * Adds various attributes (href, title, target, rel) to hyperlinks.
+ * @param {HTMLAnchorElement} link - The link element.
+ * @param {ExternalLinkParameters} params
+ */
+function addLinkAttributes(link, { url, target, rel, enabled = true } = {}) {
+  if (!url || typeof url !== "string") {
+    throw new Error('A valid "url" parameter must provided.');
+  }
+
+  const urlNullRemoved = removeNullCharacters(url);
+  if (enabled) {
+    link.href = link.title = urlNullRemoved;
+  } else {
+    link.href = "";
+    link.title = `Disabled: ${urlNullRemoved}`;
+    link.onclick = () => {
+      return false;
+    };
+  }
+
+  let targetStr = ""; // LinkTarget.NONE
+  switch (target) {
+    case LinkTarget.NONE:
+      break;
+    case LinkTarget.SELF:
+      targetStr = "_self";
+      break;
+    case LinkTarget.BLANK:
+      targetStr = "_blank";
+      break;
+    case LinkTarget.PARENT:
+      targetStr = "_parent";
+      break;
+    case LinkTarget.TOP:
+      targetStr = "_top";
+      break;
+  }
+  link.target = targetStr;
+
+  link.rel = typeof rel === "string" ? rel : DEFAULT_LINK_REL;
+}
 
 /**
  * @typedef {Object} PDFLinkServiceOptions
@@ -38,6 +102,8 @@ import { parseQueryString } from "./ui_utils.js";
  * @implements {IPDFLinkService}
  */
 class PDFLinkService {
+  #pagesRefCache = new Map();
+
   /**
    * @param {PDFLinkServiceOptions} options
    */
@@ -57,14 +123,12 @@ class PDFLinkService {
     this.pdfDocument = null;
     this.pdfViewer = null;
     this.pdfHistory = null;
-
-    this._pagesRefCache = null;
   }
 
   setDocument(pdfDocument, baseUrl = null) {
     this.baseUrl = baseUrl;
     this.pdfDocument = pdfDocument;
-    this._pagesRefCache = Object.create(null);
+    this.#pagesRefCache.clear();
   }
 
   setViewer(pdfViewer) {
@@ -110,10 +174,7 @@ class PDFLinkService {
     this.pdfViewer.pagesRotation = value;
   }
 
-  /**
-   * @private
-   */
-  _goToDestinationHelper(rawDest, namedDest = null, explicitDest) {
+  #goToDestinationHelper(rawDest, namedDest = null, explicitDest) {
     // Dest array looks like that: <page-ref> </XYZ|/FitXXX> <args..>
     const destRef = explicitDest[0];
     let pageNumber;
@@ -128,11 +189,11 @@ class PDFLinkService {
           .getPageIndex(destRef)
           .then(pageIndex => {
             this.cachePageRef(pageIndex + 1, destRef);
-            this._goToDestinationHelper(rawDest, namedDest, explicitDest);
+            this.#goToDestinationHelper(rawDest, namedDest, explicitDest);
           })
           .catch(() => {
             console.error(
-              `PDFLinkService._goToDestinationHelper: "${destRef}" is not ` +
+              `PDFLinkService.#goToDestinationHelper: "${destRef}" is not ` +
                 `a valid page reference, for dest="${rawDest}".`
             );
           });
@@ -142,14 +203,14 @@ class PDFLinkService {
       pageNumber = destRef + 1;
     } else {
       console.error(
-        `PDFLinkService._goToDestinationHelper: "${destRef}" is not ` +
+        `PDFLinkService.#goToDestinationHelper: "${destRef}" is not ` +
           `a valid destination reference, for dest="${rawDest}".`
       );
       return;
     }
     if (!pageNumber || pageNumber < 1 || pageNumber > this.pagesCount) {
       console.error(
-        `PDFLinkService._goToDestinationHelper: "${pageNumber}" is not ` +
+        `PDFLinkService.#goToDestinationHelper: "${pageNumber}" is not ` +
           `a valid page number, for dest="${rawDest}".`
       );
       return;
@@ -193,7 +254,7 @@ class PDFLinkService {
       );
       return;
     }
-    this._goToDestinationHelper(dest, namedDest, explicitDest);
+    this.#goToDestinationHelper(dest, namedDest, explicitDest);
   }
 
   /**
@@ -230,7 +291,7 @@ class PDFLinkService {
   }
 
   /**
-   * Wrapper around the `addLinkAttributes`-function in the API.
+   * Wrapper around the `addLinkAttributes` helper function.
    * @param {HTMLAnchorElement} link
    * @param {string} url
    * @param {boolean} [newWindow]
@@ -340,8 +401,7 @@ class PDFLinkService {
             }
           } else {
             console.error(
-              `PDFLinkService.setHash: "${zoomArg}" is not ` +
-                "a valid zoom value."
+              `PDFLinkService.setHash: "${zoomArg}" is not a valid zoom value.`
             );
           }
         }
@@ -379,13 +439,17 @@ class PDFLinkService {
         }
       } catch (ex) {}
 
-      if (typeof dest === "string" || isValidExplicitDestination(dest)) {
+      if (
+        typeof dest === "string" ||
+        PDFLinkService.#isValidExplicitDestination(dest)
+      ) {
         this.goToDestination(dest);
         return;
       }
       console.error(
-        `PDFLinkService.setHash: "${unescape(hash)}" is not ` +
-          "a valid destination."
+        `PDFLinkService.setHash: "${unescape(
+          hash
+        )}" is not a valid destination.`
       );
     }
   }
@@ -440,11 +504,11 @@ class PDFLinkService {
     }
     const refStr =
       pageRef.gen === 0 ? `${pageRef.num}R` : `${pageRef.num}R${pageRef.gen}`;
-    this._pagesRefCache[refStr] = pageNum;
+    this.#pagesRefCache.set(refStr, pageNum);
   }
 
   /**
-   * @private
+   * @ignore
    */
   _cachedPageNumber(pageRef) {
     if (!pageRef) {
@@ -452,7 +516,7 @@ class PDFLinkService {
     }
     const refStr =
       pageRef.gen === 0 ? `${pageRef.num}R` : `${pageRef.num}R${pageRef.gen}`;
-    return this._pagesRefCache?.[refStr] || null;
+    return this.#pagesRefCache.get(refStr) || null;
   }
 
   /**
@@ -468,65 +532,65 @@ class PDFLinkService {
   isPageCached(pageNumber) {
     return this.pdfViewer.isPageCached(pageNumber);
   }
-}
 
-function isValidExplicitDestination(dest) {
-  if (!Array.isArray(dest)) {
-    return false;
-  }
-  const destLength = dest.length;
-  if (destLength < 2) {
-    return false;
-  }
-  const page = dest[0];
-  if (
-    !(
-      typeof page === "object" &&
-      Number.isInteger(page.num) &&
-      Number.isInteger(page.gen)
-    ) &&
-    !(Number.isInteger(page) && page >= 0)
-  ) {
-    return false;
-  }
-  const zoom = dest[1];
-  if (!(typeof zoom === "object" && typeof zoom.name === "string")) {
-    return false;
-  }
-  let allowNull = true;
-  switch (zoom.name) {
-    case "XYZ":
-      if (destLength !== 5) {
-        return false;
-      }
-      break;
-    case "Fit":
-    case "FitB":
-      return destLength === 2;
-    case "FitH":
-    case "FitBH":
-    case "FitV":
-    case "FitBV":
-      if (destLength !== 3) {
-        return false;
-      }
-      break;
-    case "FitR":
-      if (destLength !== 6) {
-        return false;
-      }
-      allowNull = false;
-      break;
-    default:
-      return false;
-  }
-  for (let i = 2; i < destLength; i++) {
-    const param = dest[i];
-    if (!(typeof param === "number" || (allowNull && param === null))) {
+  static #isValidExplicitDestination(dest) {
+    if (!Array.isArray(dest)) {
       return false;
     }
+    const destLength = dest.length;
+    if (destLength < 2) {
+      return false;
+    }
+    const page = dest[0];
+    if (
+      !(
+        typeof page === "object" &&
+        Number.isInteger(page.num) &&
+        Number.isInteger(page.gen)
+      ) &&
+      !(Number.isInteger(page) && page >= 0)
+    ) {
+      return false;
+    }
+    const zoom = dest[1];
+    if (!(typeof zoom === "object" && typeof zoom.name === "string")) {
+      return false;
+    }
+    let allowNull = true;
+    switch (zoom.name) {
+      case "XYZ":
+        if (destLength !== 5) {
+          return false;
+        }
+        break;
+      case "Fit":
+      case "FitB":
+        return destLength === 2;
+      case "FitH":
+      case "FitBH":
+      case "FitV":
+      case "FitBV":
+        if (destLength !== 3) {
+          return false;
+        }
+        break;
+      case "FitR":
+        if (destLength !== 6) {
+          return false;
+        }
+        allowNull = false;
+        break;
+      default:
+        return false;
+    }
+    for (let i = 2; i < destLength; i++) {
+      const param = dest[i];
+      if (!(typeof param === "number" || (allowNull && param === null))) {
+        return false;
+      }
+    }
+    return true;
   }
-  return true;
 }
 
 /**
@@ -634,4 +698,4 @@ class SimpleLinkService {
   }
 }
 
-export { PDFLinkService, SimpleLinkService };
+export { LinkTarget, PDFLinkService, SimpleLinkService };
diff --git a/web/pdf_viewer.component.js b/web/pdf_viewer.component.js
index dce7d9b93..a7a918cf1 100644
--- a/web/pdf_viewer.component.js
+++ b/web/pdf_viewer.component.js
@@ -19,7 +19,11 @@ import {
   DefaultTextLayerFactory,
   DefaultXfaLayerFactory,
 } from "./default_factory.js";
-import { PDFLinkService, SimpleLinkService } from "./pdf_link_service.js";
+import {
+  LinkTarget,
+  PDFLinkService,
+  SimpleLinkService,
+} from "./pdf_link_service.js";
 import { PDFSinglePageViewer, PDFViewer } from "./pdf_viewer.js";
 import { AnnotationLayerBuilder } from "./annotation_layer_builder.js";
 import { DownloadManager } from "./download_manager.js";
@@ -49,6 +53,7 @@ export {
   DownloadManager,
   EventBus,
   GenericL10n,
+  LinkTarget,
   NullL10n,
   PDFFindController,
   PDFHistory,
diff --git a/web/ui_utils.js b/web/ui_utils.js
index d446cda3d..54593573a 100644
--- a/web/ui_utils.js
+++ b/web/ui_utils.js
@@ -200,6 +200,24 @@ function parseQueryString(query) {
   return params;
 }
 
+const NullCharactersRegExp = /\x00/g;
+const InvisibleCharactersRegExp = /[\x01-\x1F]/g;
+
+/**
+ * @param {string} str
+ * @param {boolean} [replaceInvisible]
+ */
+function removeNullCharacters(str, replaceInvisible = false) {
+  if (typeof str !== "string") {
+    console.error(`The argument must be a string.`);
+    return str;
+  }
+  if (replaceInvisible) {
+    str = str.replace(InvisibleCharactersRegExp, " ");
+  }
+  return str.replace(NullCharactersRegExp, "");
+}
+
 /**
  * Use binary search to find the index of the first item in a given array which
  * passes a given condition. The items are expected to be sorted in the sense
@@ -838,6 +856,7 @@ export {
   parseQueryString,
   PresentationModeState,
   ProgressBar,
+  removeNullCharacters,
   RendererType,
   RenderingStates,
   roundToDivide,