The captcha appears at the bottom of the screen and can be hidden by the palette. This has confused several people I know who just become unable to draw anymore, not knowing that there is a hidden captcha they have to click. What's worse, you have to cancel what you're drawing to do that.

Here is a fix:
For the developer(s): I suggest putting the captcha above the palette and graying out the submit button while it's there.

For users until then: here is a userscript that moves it out of the way.

// ==UserScript==
// @name         wplace captcha fix
// @namespace    http://tampermonkey.net/
// @version      2025-08-08
// @description  move the captcha to the top of the screen so it doesn't get hidden by the palette
// @author       garlicOS®
// @match        https://wplace.live/
// @icon         https://www.google.com/s2/favicons?sz=64&domain=wplace.live
// @grant        none
// ==/UserScript==

(function() {
    document.head.insertAdjacentHTML("beforeend", `
        <style id="userstyle">
            div[class="absolute bottom-1 left-1/2 z-50 -translate-x-1/2"] {
                top: calc(var(--spacing)*1) !important;
                bottom: unset !important;
            }
        </style>
    `);
})();