2025.10.0-rc: Script exceeds 64 KB limit

Extensions
1

I’ve got a admin extension running under

    "@shopify/ui-extensions": "2025.1.x",
    "@shopify/ui-extensions-react": "2025.1.x",
    "country-state-city": "^3.2.1",
    "react": "^18.0.0",
    "react-reconciler": "0.29.0"

Which is being built into a compact JS script of size 728Kb and it is being deployed and running successfully within the target section.

Now I’m trying to rewrite it into preact + Polaris web components built under

    "preact": "^10.27.1",
    "@shopify/ui-extensions": "~2025.10.0-rc",
    "country-state-city": "^3.2.1"

It has decreased the resulting JS file’s size to 634Kb, but when I’m trying to deploy it, I would see this error from shopify CLI:

╭─ error ────────────────────────────────────────────────────╮
│                                                            │
│  Version couldn't be created.                              │
│                                                            │
│  my-super-ui                                               │
│                                                            │
│  Validation errors                                         │
│    • Script exceeds 64 KB limit                            │
│                                                            │
╰────────────────────────────────────────────────────────────╯

I’m not sure if I had messed up my build configuration in the process of migrating to preact or is this just a new restriction only affecting version 2025-10. Or is this a bug on the deployment server’s side?

Could please someone help me interpret this odd situation.

Thanks!

1 Like
2

Seeing the same thing here, works fine under 2025-07 - but fails on 2025-10-rc

1 Like
3

As of 2025-10, UI extensions will have an enforced 64 KB filesize limit upon deployment. I believe you’ll also see a warning while in development (shopify app dev).

I would look into what the filesize difference (you can check within the extension’s /dist) when removing the country-state-city dependency as looking at that it seems it’s quite large.

3 Likes
4

Not sure what’s happening here, but I have an app with multiple POS UI extensions. As soon as I switch any of the POS extensions to 2025-10 I get the error:

16:14:56 │               app-preview │ ❌ Error
16:14:56 │      multi-barcode-switch │ └  Your script size is 74 KB which exceeds the 64 KB limit

Though the extension is super basic so if it doesn’t fit the size, I don’t see how any POS extension can fit that size. (it’s also always saying 74KB regarless of which extension I enable)

5

Are you also updating to Polaris UI (s-stack, etc) or are you using Polaris-React?

As part of 2025-10, you’ll need to update away from the React version since that package will make it hard to hit 64kb. Upgrading to 2025-10