YoHoHo.io

WebGLReport should confirm support for WebGL v1. 'Unmasked Renderer' should show your GPU name. If 'Google SwiftShader' is shown, your browser is using a CPU renderer and hardware acceleration is disabled.
Check you have the latest version for your browser
Check hardware acceleration is enabled for your browser
Check WebGL is enabled for your browser
Update your graphics drivers

Chrome

Open "Menu | Settings..." and search for 'hardware'. Ensure setting 'Use hardware acceleration when available' is enabled.

After restarting chrome, enter chrome://gpu/ in your address bar: it should now show 'Hardware accelerated' for WebGL. If not, try to enable 'Override software rendering list' in chrome://flags/#ignore-gpu-blocklist

Safari

Open "Safari | Preferences...", select 'Security' and enable 'Allow WebGL' setting

Firefox

Open about:config and check 'webgl.disabled' is set to 'false'

In settings, under 'Performance', check 'Use hardware acceleration when available' is enabled.

How can I improve the game performance on a Windows laptop?

Plug-in your charger while playing to avoid Windows lowering performance to save battery
If you have an NVIDIA GPU, make sure it's being used by your browser (eg Chrome). Check this guide or this one.
If you have an ATI/AMD Radeon card, open the Catalyst Control Center, go to Graphics > PowerPlay - Set Plugged In to Maximum Performance. Click Apply.
To determine which GPU is actually being used, go there and look at "Unmasked Renderer". Alternatively, you can right-click the chrome.exe shortcut and force a specific graphics processor within the menu.
If you have no additional GPU but an integrated Intel GPU, make sure it's set to "Maximum performance" when Plugged In: open Intel Graphics settings, click "Power", "Plugged-In" and select "Maximum Performance" (check this guide for more details)
Switch to a high-performance power plan when plugged-in, check this guide
Close other tabs/applications that may consume CPU/GPU resources or internet bandwidth
Prefer wired (ethernet) over wifi

Why is my progress not saved?

If you have not created an account, your progress is saved within your browser's local storage. Make sure cookies are not cleared when exiting.

Do not use incognito mode, it clears cookies when you exit the browser.
On iPad/iPhone, uncheck "Block Cookies" in Settings > Safari > Privacy & Security.
Check for any privacy plugin that blocks or deletes cookies.

Google sign-in issues

If you use chrome, try to logout from the browser (top-right icon) or on myaccount.google.com
Alternatively, try to delete your cookies for "accounts.google.com" and ONLY THIS DOMAIN
Make sure your browser or one of your browser plugins (privacy plugins, adblock...) is not blocking social plugins/buttons.
To sign-in with google in incognito mode, you need to enable specific cookies, see the documentation here

Help / FAQ