diff --git a/baselines/dom.generated.d.ts b/baselines/dom.generated.d.ts
index 0c1439308..449cea7ba 100644
--- a/baselines/dom.generated.d.ts
+++ b/baselines/dom.generated.d.ts
@@ -4026,6 +4026,7 @@ interface DOMMatrixReadOnly {
     toJSON(): any;
     transformPoint(point?: DOMPointInit): DOMPoint;
     translate(tx?: number, ty?: number, tz?: number): DOMMatrix;
+    toString(): string;
 }
 
 declare var DOMMatrixReadOnly: {
@@ -4034,6 +4035,7 @@ declare var DOMMatrixReadOnly: {
     fromFloat32Array(array32: Float32Array): DOMMatrixReadOnly;
     fromFloat64Array(array64: Float64Array): DOMMatrixReadOnly;
     fromMatrix(other?: DOMMatrixInit): DOMMatrixReadOnly;
+    toString(): string;
 };
 
 /** Provides the ability to parse XML or HTML source code from a string into a DOM Document. */
@@ -4191,6 +4193,7 @@ interface DOMTokenList {
      * Can be set, to change the associated attribute.
      */
     value: string;
+    toString(): string;
     /**
      * Adds all arguments passed, except those already present.
      * 
@@ -7071,6 +7074,7 @@ interface HTMLHyperlinkElementUtils {
     host: string;
     hostname: string;
     href: string;
+    toString(): string;
     readonly origin: string;
     password: string;
     pathname: string;
@@ -9924,6 +9928,7 @@ interface Location {
      * Can be set, to navigate to the given URL.
      */
     href: string;
+    toString(): string;
     /**
      * Returns the Location object's URL's origin.
      */
@@ -10382,10 +10387,10 @@ declare var MediaKeys: {
 interface MediaList {
     readonly length: number;
     mediaText: string;
+    toString(): string;
     appendMedium(medium: string): void;
     deleteMedium(medium: string): void;
     item(index: number): string | null;
-    toString(): number;
     [index: number]: string;
 }
 
@@ -12652,6 +12657,7 @@ interface Range extends AbstractRange {
     setStartAfter(node: Node): void;
     setStartBefore(node: Node): void;
     surroundContents(newParent: Node): void;
+    toString(): string;
     readonly END_TO_END: number;
     readonly END_TO_START: number;
     readonly START_TO_END: number;
@@ -12665,6 +12671,7 @@ declare var Range: {
     readonly END_TO_START: number;
     readonly START_TO_END: number;
     readonly START_TO_START: number;
+    toString(): string;
 };
 
 interface ReadableByteStreamController {
@@ -15036,11 +15043,13 @@ interface Selection {
     selectAllChildren(node: Node): void;
     setBaseAndExtent(anchorNode: Node, anchorOffset: number, focusNode: Node, focusOffset: number): void;
     setPosition(node: Node | null, offset?: number): void;
+    toString(): string;
 }
 
 declare var Selection: {
     prototype: Selection;
     new(): Selection;
+    toString(): string;
 };
 
 interface ServiceUIFrameContext {
@@ -16045,6 +16054,7 @@ interface URL {
     host: string;
     hostname: string;
     href: string;
+    toString(): string;
     readonly origin: string;
     password: string;
     pathname: string;
@@ -16092,12 +16102,14 @@ interface URLSearchParams {
      */
     set(name: string, value: string): void;
     sort(): void;
+    toString(): string;
     forEach(callbackfn: (value: string, key: string, parent: URLSearchParams) => void, thisArg?: any): void;
 }
 
 declare var URLSearchParams: {
     prototype: URLSearchParams;
     new(init?: string[][] | Record<string, string> | string | URLSearchParams): URLSearchParams;
+    toString(): string;
 };
 
 /** This WebVR API interface represents any VR device supported by this API. It includes generic information such as device IDs and descriptions, as well as methods for starting to present a VR scene, retrieving eye parameters and display capabilities, and other important functionality. */
diff --git a/baselines/webworker.generated.d.ts b/baselines/webworker.generated.d.ts
index 492e7951a..111b94ad0 100644
--- a/baselines/webworker.generated.d.ts
+++ b/baselines/webworker.generated.d.ts
@@ -3211,6 +3211,7 @@ interface URL {
     host: string;
     hostname: string;
     href: string;
+    toString(): string;
     readonly origin: string;
     password: string;
     pathname: string;
@@ -3255,12 +3256,14 @@ interface URLSearchParams {
      */
     set(name: string, value: string): void;
     sort(): void;
+    toString(): string;
     forEach(callbackfn: (value: string, key: string, parent: URLSearchParams) => void, thisArg?: any): void;
 }
 
 declare var URLSearchParams: {
     prototype: URLSearchParams;
     new(init?: string[][] | Record<string, string> | string | URLSearchParams): URLSearchParams;
+    toString(): string;
 };
 
 interface WEBGL_color_buffer_float {
@@ -5389,12 +5392,12 @@ interface WorkerLocation {
     readonly host: string;
     readonly hostname: string;
     readonly href: string;
+    toString(): string;
     readonly origin: string;
     readonly pathname: string;
     readonly port: string;
     readonly protocol: string;
     readonly search: string;
-    toString(): string;
 }
 
 declare var WorkerLocation: {
diff --git a/src/emitter.ts b/src/emitter.ts
index 3f4669833..5f23a60d0 100644
--- a/src/emitter.ts
+++ b/src/emitter.ts
@@ -626,6 +626,10 @@ export function emitWebIdl(webidl: Browser.WebIdl, flavor: Flavor) {
             const readOnlyModifier = p["read-only"] === 1 && prefix === "" ? "readonly " : "";
             printer.printLine(`${prefix}${readOnlyModifier}${p.name}${requiredModifier}: ${pType};`);
         }
+
+        if (p.stringifier) {
+            printer.printLine("toString(): string;")
+        }
     }
 
     function emitComments(entity: { comment?: string; deprecated?: 1 }, print: (s: string) => void) {
@@ -666,7 +670,16 @@ export function emitWebIdl(webidl: Browser.WebIdl, flavor: Flavor) {
             case "querySelector": return emitQuerySelectorOverloads(m);
             case "querySelectorAll": return emitQuerySelectorAllOverloads(m);
         }
-        emitSignatures(m, prefix, m.name, printLine);
+
+        // ignore toString() provided from browser.webidl.preprocessed.json
+        // to prevent duplication
+        if (m.name !== "toString") {
+            emitSignatures(m, prefix, m.name, printLine);
+
+            if (m.stringifier) {
+                printLine("toString(): string;")
+            }
+        }
     }
 
     function emitSignature(s: Browser.Signature, prefix: string | undefined, name: string | undefined, printLine: (s: string) => void) {
@@ -698,6 +711,12 @@ export function emitWebIdl(webidl: Browser.WebIdl, flavor: Flavor) {
                 .sort(compareName)
                 .forEach(m => emitMethod(prefix, m, conflictedMembers));
         }
+        if (i["anonymous-methods"]) {
+            const stringifier = i["anonymous-methods"].method.find(m => m.stringifier);
+            if (stringifier) {
+                printer.printLine("toString(): string;");
+            }
+        }
 
         // The window interface inherited some methods from "Object",
         // which need to explicitly exposed
diff --git a/src/widlprocess.ts b/src/widlprocess.ts
index 9c65a5614..7372dcf9f 100644
--- a/src/widlprocess.ts
+++ b/src/widlprocess.ts
@@ -145,7 +145,7 @@ function convertInterfaceCommon(i: webidl2.InterfaceType | webidl2.InterfaceMixi
                 properties!.property[member.name] = prop;
             }
         }
-        else if (member.type === "operation" && member.idlType) {
+        else if (member.type === "operation") {
             const operation = convertOperation(member, result.exposed);
             const { method } = result.methods;
             if (!member.name) {
@@ -205,18 +205,23 @@ function getNamedConstructor(extAttrs: webidl2.ExtendedAttribute[], parent: stri
 }
 
 function convertOperation(operation: webidl2.OperationMemberType, inheritedExposure: string | undefined): Browser.AnonymousMethod | Browser.Method {
-    if (!operation.idlType) {
+    const isStringifier = operation.special === "stringifier";
+    const type =
+        operation.idlType ? convertIdlType(operation.idlType) :
+        isStringifier ? { type: "DOMString" } :
+        undefined;
+    if (!type) {
         throw new Error("Unexpected anonymous operation");
     }
     return {
         name: operation.name || undefined,
         signature: [{
-            ...convertIdlType(operation.idlType),
+            ...type,
             param: operation.arguments.map(convertArgument)
         }],
         getter: operation.special === "getter" ? 1 : undefined,
         static: operation.special === "static" ? 1 : undefined,
-        stringifier: operation.special === "stringifier" ? 1 : undefined,
+        stringifier: isStringifier ? 1 : undefined,
         exposed: getExtAttrConcatenated(operation.extAttrs, "Exposed") || inheritedExposure
     };
 }
@@ -249,6 +254,7 @@ function convertAttribute(attribute: webidl2.AttributeMemberType, inheritedExpos
         name: attribute.name,
         ...convertIdlType(attribute.idlType),
         static: attribute.special === "static" ? 1 : undefined,
+        stringifier: attribute.special === "stringifier" ? 1 : undefined,
         "read-only": attribute.readonly ? 1 : undefined,
         "event-handler": isEventHandler ? attribute.name.slice(2) : undefined,
         exposed: getExtAttrConcatenated(attribute.extAttrs, "Exposed") || inheritedExposure