Edit the Uploadery error messages
Follow the steps below to edit the error messages that appear when a user uploads a file that doesn't meet the set requirements.
1. From your Shopify admin, click Online Store, then click Themes.
2. Find the theme you want to edit, click the Actions button, then click Edit HTML/CSS.
3. On the left side, under the Layout heading, click on the theme.liquid file.
4. Copy the following code snippet.
5. Paste it directly after the <head> tag.
6. Replace the text within the quotes with your desired error message (don't remove the quotes!).
7. Save your changes.