diff --git a/README.md b/README.md
index da798ba..7af556e 100644
--- a/README.md
+++ b/README.md
@@ -287,12 +287,17 @@ None.
 ## Supported browser engines
 
 * Gecko (Firefox): works in v132, both with JS enabled (offline mode) and with JS disabled (plain old client-server mode).
-* Blink (e.g. Chromium and Chromium-based browsers): not checked, should work in reasonably recent versions,
-    both with JS enabled (offline mode) and with JS disabled (plain old client-server mode).
+    Should work in offline mode starting with Firefox 63 (2018); should work in plain old client-server mode in all versions,
+    although the design in Firefox 51 (2017) and older will probably not look very good due to the lack of the recent CSS features.
+* Blink (e.g. Chromium and Chromium-based browsers): superficially checked in Chromium 130, basic functionality seems to work.
+    Should work in offline mode starting with Chrome 67 (2018); should work in plain old client-server mode in all versions,
+    although the design in Chrome 56 (2017) and older will probably not look very good due to the lack of the recent CSS features.
 * WebKit (e.g. qutebrowser and notably Safari): not checked; should **not** work in offline mode,
     because WebKit does not fully implement decade-old standard which Gecko and Blink supported since 2018:
     https://github.com/WebKit/standards-positions/issues/97.
-    Everything should still work in online mode, falling back on client-server communication.
+    Everything should still work in online mode, falling back on client-server communication,
+    except that the design in Safari before 10.1 (2017) will not look very good (but will still be functional),
+    and will probably become disfunctional in Safari before 3.1 (2008).
 * Servo: checked, does **not** work in nightly as of 2024-11-20, and I don't have an opportunity to figure out why
     (it's not packaged for Alpine (...yet), their regular Linux builds don't work on Alpine,
     so I had to check it on someone else's Windows machine).
@@ -315,10 +320,6 @@ None.
 * Implement error handling and handling of incorrect / malformed game states (since they come from the client).
 * Improve UI for large boards (disable autoplayers when board is too large,
     hide "enable autoplayer" buttons, provide clear indication to the user instead).
-* Target older ES versions on the frontend,
-    so that offline-only game can work in all browsers fully supporting Web Components
-    (i.e. Blink-based and Firefox not older than 2018);
-    right now ES2022 is targeted.
 * Figure out better API for game board,
     `board.get(row, column)` and `board.get(row, column)` seemed to be a good way to encapsulate readonly state,
     but they became very inconvenient as the codebase grew and became more complex,
diff --git a/src/frontend/components/board-game.ts b/src/frontend/components/board-game.ts
index ac8f7b5..71df33d 100644
--- a/src/frontend/components/board-game.ts
+++ b/src/frontend/components/board-game.ts
@@ -24,20 +24,20 @@ export class BoardGameComponent extends HTMLElement {
       return;
     }
 
-    for (const playerNameElement of this.querySelectorAll(".current-player-name")) {
+    this.querySelectorAll(".current-player-name").forEach((playerNameElement) => {
       if ((playerNameElement as HTMLElement).innerText !== gameState.currentPlayerName) {
         (playerNameElement as HTMLElement).innerText = gameState.currentPlayerName;
       }
-    }
+    });
 
     const buttonValues = getButtonValues(gameState);
-    for (const button of this.querySelectorAll("button")) {
-      for (const className of button.classList) {
-        if (Object.hasOwn(buttonValues, className)) {
+    this.querySelectorAll("button").forEach((button) => {
+      button.classList.forEach((className) => {
+        if (Object.prototype.hasOwnProperty.call(buttonValues, className)) {
           button.value = buttonValues[className as keyof ButtonValues].serialize();
         }
-      }
-    }
+      });
+    });
 
     const currentOutcome = gameState.board ? rules.getBoardOutcome(gameState.board) : CurrentOutcome.Undecided;
 
@@ -46,7 +46,7 @@ export class BoardGameComponent extends HTMLElement {
       this.classList.toggle(className, shouldEnable);
     }
 
-    for (const tbodyUntyped of this.querySelectorAll("tbody.game-board")) {
+    this.querySelectorAll("tbody.game-board").forEach((tbodyUntyped) => {
       const tbody = tbodyUntyped as HTMLTableSectionElement;
 
       while (gameState.rows < tbody.rows.length) {
@@ -90,7 +90,7 @@ export class BoardGameComponent extends HTMLElement {
             row: rowNumber,
             column: columnNumber,
           });
-          for (const button of cell.querySelectorAll("button")) {
+          cell.querySelectorAll("button").forEach((button) => {
             button.value = nextGameState.serialize();
             if (button.disabled !== isDisabled) {
               button.disabled = isDisabled;
@@ -101,10 +101,10 @@ export class BoardGameComponent extends HTMLElement {
             if (button.className !== className) {
               button.className = className;
             }
-          }
+          });
         }
       }
-    }
+    });
   }
 
   connectedCallback() {
diff --git a/src/frontend/components/progressive-form.ts b/src/frontend/components/progressive-form.ts
index e7f998f..90c797f 100644
--- a/src/frontend/components/progressive-form.ts
+++ b/src/frontend/components/progressive-form.ts
@@ -1,8 +1,18 @@
 import { goToLocation } from "../utils/navigation-utils.ts";
 import { updateWithQueryParams } from "../utils/url-utils.ts";
 
+// Needed for backwards compatibility with browsers that predate FormData as iterator
+const getFormDataEntries = (formData: FormData) => {
+  const result: [string, FormDataEntryValue][] = [];
+  formData.forEach((value, key) => {
+    result.push([key, value]);
+  });
+
+  return result;
+};
+
 const submitListener = function (this: HTMLFormElement, e: SubmitEvent) {
-  goToLocation(updateWithQueryParams(new URL(this.action), new FormData(this, e.submitter)));
+  goToLocation(updateWithQueryParams(new URL(this.action), getFormDataEntries(new FormData(this, e.submitter))));
   e.preventDefault();
 };
 
diff --git a/tsconfig.json b/tsconfig.json
index 388bb0b..c3ba1be 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -6,8 +6,9 @@
     "forceConsistentCasingInFileNames": true,
     "jsx": "react-jsx",
     "jsxImportSource": "preact",
+    "lib": ["DOM", "ES6"],
     "module": "NodeNext",
     "noEmit": true,
-    "target": "ES2022"
+    "target": "ES6"
   }
 }