diff --git a/frontend/src/ts/commandline/lists.ts b/frontend/src/ts/commandline/lists.ts
index 100032beff17..d6965c3f5616 100644
--- a/frontend/src/ts/commandline/lists.ts
+++ b/frontend/src/ts/commandline/lists.ts
@@ -108,6 +108,7 @@ import * as FPSCounter from "../elements/fps-counter";
 import { migrateConfig } from "../utils/config";
 import { PartialConfigSchema } from "@monkeytype/contracts/schemas/configs";
 import { Command, CommandsSubgroup } from "./types";
+import { parseWithSchema as parseJsonWithSchema } from "@monkeytype/util/json";
 
 const layoutsPromise = JSONData.getLayoutsList();
 layoutsPromise
@@ -362,8 +363,9 @@ export const commands: CommandsSubgroup = {
       exec: async ({ input }): Promise<void> => {
         if (input === undefined || input === "") return;
         try {
-          const parsedConfig = PartialConfigSchema.strip().parse(
-            JSON.parse(input)
+          const parsedConfig = parseJsonWithSchema(
+            input,
+            PartialConfigSchema.strip()
           );
           await UpdateConfig.apply(migrateConfig(parsedConfig));
           UpdateConfig.saveFullConfigToLocalStorage();
diff --git a/frontend/src/ts/controllers/analytics-controller.ts b/frontend/src/ts/controllers/analytics-controller.ts
index 56fbc7eaf086..afb7df31c37b 100644
--- a/frontend/src/ts/controllers/analytics-controller.ts
+++ b/frontend/src/ts/controllers/analytics-controller.ts
@@ -6,13 +6,17 @@ import {
 } from "firebase/analytics";
 import { app as firebaseApp } from "../firebase";
 import { createErrorMessage } from "../utils/misc";
+import { parseWithSchema as parseJsonWithSchema } from "@monkeytype/util/json";
+import { z } from "zod";
 
 let analytics: AnalyticsType;
 
-type AcceptedCookies = {
-  security: boolean;
-  analytics: boolean;
-};
+const AcceptedCookiesSchema = z.object({
+  security: z.boolean(),
+  analytics: z.boolean(),
+});
+
+type AcceptedCookies = z.infer<typeof AcceptedCookiesSchema>;
 
 export async function log(
   eventName: string,
@@ -26,9 +30,14 @@ export async function log(
 }
 
 const lsString = localStorage.getItem("acceptedCookies");
-let acceptedCookies;
+let acceptedCookies: AcceptedCookies | null;
 if (lsString !== undefined && lsString !== null && lsString !== "") {
-  acceptedCookies = JSON.parse(lsString) as AcceptedCookies;
+  try {
+    acceptedCookies = parseJsonWithSchema(lsString, AcceptedCookiesSchema);
+  } catch (e) {
+    console.error("Failed to parse accepted cookies:", e);
+    acceptedCookies = null;
+  }
 } else {
   acceptedCookies = null;
 }
diff --git a/frontend/src/ts/event-handlers/account.ts b/frontend/src/ts/event-handlers/account.ts
index af42fdc14a23..d9327ad794d0 100644
--- a/frontend/src/ts/event-handlers/account.ts
+++ b/frontend/src/ts/event-handlers/account.ts
@@ -5,6 +5,8 @@ import { isAuthenticated } from "../firebase";
 import * as Notifications from "../elements/notifications";
 import * as EditResultTagsModal from "../modals/edit-result-tags";
 import * as AddFilterPresetModal from "../modals/new-filter-preset";
+import { parseWithSchema as parseJsonWithSchema } from "@monkeytype/util/json";
+import { z } from "zod";
 
 const accountPage = document.querySelector("#pageAccount") as HTMLElement;
 
@@ -36,12 +38,15 @@ $(accountPage).on("click", ".editProfileButton", () => {
   EditProfileModal.show();
 });
 
+const TagsArraySchema = z.array(z.string());
+
 $(accountPage).on("click", ".group.history .resultEditTagsButton", (e) => {
   const resultid = $(e.target).attr("data-result-id");
   const tags = $(e.target).attr("data-tags");
+
   EditResultTagsModal.show(
     resultid ?? "",
-    JSON.parse(tags ?? "[]") as string[],
+    parseJsonWithSchema(tags ?? "[]", TagsArraySchema),
     "accountPage"
   );
 });
diff --git a/frontend/src/ts/modals/import-export-settings.ts b/frontend/src/ts/modals/import-export-settings.ts
index ff0cb82d4add..1994064dc1ee 100644
--- a/frontend/src/ts/modals/import-export-settings.ts
+++ b/frontend/src/ts/modals/import-export-settings.ts
@@ -3,6 +3,7 @@ import * as UpdateConfig from "../config";
 import * as Notifications from "../elements/notifications";
 import AnimatedModal from "../utils/animated-modal";
 import { migrateConfig } from "../utils/config";
+import { parseWithSchema as parseJsonWithSchema } from "@monkeytype/util/json";
 
 type State = {
   mode: "import" | "export";
@@ -47,8 +48,9 @@ const modal = new AnimatedModal({
         return;
       }
       try {
-        const parsedConfig = PartialConfigSchema.strip().parse(
-          JSON.parse(state.value)
+        const parsedConfig = parseJsonWithSchema(
+          state.value,
+          PartialConfigSchema.strip()
         );
         await UpdateConfig.apply(migrateConfig(parsedConfig));
       } catch (e) {
diff --git a/frontend/src/ts/test/custom-text.ts b/frontend/src/ts/test/custom-text.ts
index a0d59cb2ff44..9837fc554656 100644
--- a/frontend/src/ts/test/custom-text.ts
+++ b/frontend/src/ts/test/custom-text.ts
@@ -29,7 +29,7 @@ const customTextLongLS = new LocalStorageWithSchema({
   fallback: {},
 });
 
-const CustomTextSettingsSchema = z.object({
+export const CustomTextSettingsSchema = z.object({
   text: z.array(z.string()),
   mode: CustomTextModeSchema,
   limit: z.object({ value: z.number(), mode: CustomTextLimitModeSchema }),
diff --git a/frontend/src/ts/test/wikipedia.ts b/frontend/src/ts/test/wikipedia.ts
index 5bed9a7c6749..44a616ce088b 100644
--- a/frontend/src/ts/test/wikipedia.ts
+++ b/frontend/src/ts/test/wikipedia.ts
@@ -2,6 +2,8 @@ import * as Loader from "../elements/loader";
 import * as Misc from "../utils/misc";
 import * as Strings from "../utils/strings";
 import * as JSONData from "../utils/json-data";
+import { z } from "zod";
+import { parseWithSchema as parseJsonWithSchema } from "@monkeytype/util/json";
 
 export async function getTLD(
   languageGroup: JSONData.LanguageGroup
@@ -241,6 +243,18 @@ type SectionObject = {
   author: string;
 };
 
+// Section Schema
+const SectionSchema = z.object({
+  query: z.object({
+    pages: z.record(
+      z.string(),
+      z.object({
+        extract: z.string(),
+      })
+    ),
+  }),
+});
+
 export async function getSection(language: string): Promise<JSONData.Section> {
   // console.log("Getting section");
   Loader.show();
@@ -285,10 +299,17 @@ export async function getSection(language: string): Promise<JSONData.Section> {
     sectionReq.onload = (): void => {
       if (sectionReq.readyState === 4) {
         if (sectionReq.status === 200) {
-          // eslint-disable-next-line @typescript-eslint/no-unsafe-member-access
-          let sectionText = JSON.parse(sectionReq.responseText).query.pages[
-            pageid.toString()
-          ].extract as string;
+          const parsedResponse = parseJsonWithSchema(
+            sectionReq.responseText,
+            SectionSchema
+          );
+          const page = parsedResponse.query.pages[pageid.toString()];
+          if (!page) {
+            Loader.hide();
+            rej("Page not found");
+            return;
+          }
+          let sectionText = page.extract;
 
           // Converting to one paragraph
           sectionText = sectionText.replace(/<\/p><p>+/g, " ");
diff --git a/frontend/src/ts/utils/url-handler.ts b/frontend/src/ts/utils/url-handler.ts
index 036e8d4700eb..352a258ba7ad 100644
--- a/frontend/src/ts/utils/url-handler.ts
+++ b/frontend/src/ts/utils/url-handler.ts
@@ -11,7 +11,11 @@ import * as Loader from "../elements/loader";
 import * as AccountButton from "../elements/account-button";
 import { restart as restartTest } from "../test/test-logic";
 import * as ChallengeController from "../controllers/challenge-controller";
-import { Mode, Mode2 } from "@monkeytype/contracts/schemas/shared";
+import {
+  DifficultySchema,
+  Mode2Schema,
+  ModeSchema,
+} from "@monkeytype/contracts/schemas/shared";
 import {
   CustomBackgroundFilter,
   CustomBackgroundFilterSchema,
@@ -19,7 +23,6 @@ import {
   CustomBackgroundSizeSchema,
   CustomThemeColors,
   CustomThemeColorsSchema,
-  Difficulty,
 } from "@monkeytype/contracts/schemas/configs";
 import { z } from "zod";
 import { parseWithSchema as parseJsonWithSchema } from "@monkeytype/util/json";
@@ -129,24 +132,36 @@ export function loadCustomThemeFromUrl(getOverride?: string): void {
   }
 }
 
-type SharedTestSettings = [
-  Mode | null,
-  Mode2<Mode> | null,
-  CustomText.CustomTextData | null,
-  boolean | null,
-  boolean | null,
-  string | null,
-  Difficulty | null,
-  string | null
-];
+const TestSettingsSchema = z.tuple([
+  ModeSchema.nullable(),
+  Mode2Schema.nullable(),
+  CustomText.CustomTextSettingsSchema.nullable(),
+  z.boolean().nullable(), //punctuation
+  z.boolean().nullable(), //numbers
+  z.string().nullable(), //language
+  DifficultySchema.nullable(),
+  z.string().nullable(), //funbox
+]);
+
+type SharedTestSettings = z.infer<typeof TestSettingsSchema>;
 
 export function loadTestSettingsFromUrl(getOverride?: string): void {
   const getValue = Misc.findGetParameter("testSettings", getOverride);
   if (getValue === null) return;
 
-  const de = JSON.parse(
-    decompressFromURI(getValue) ?? ""
-  ) as SharedTestSettings;
+  let de: SharedTestSettings;
+  try {
+    const decompressed = decompressFromURI(getValue) ?? "";
+    const parsed = parseJsonWithSchema(decompressed, TestSettingsSchema);
+    de = parsed as SharedTestSettings; // Assign after refinement
+  } catch (e) {
+    console.error("Failed to parse test settings:", e);
+    Notifications.add(
+      "Failed to load test settings from URL: " + (e as Error).message,
+      0
+    );
+    return;
+  }
 
   const applied: Record<string, string> = {};