Works with Shopify
Shopify renders Liquid templates on the server, so your storefront text is in the HTML response the crawler reads.
Shopify, free beta
DraftMine's Website Humanizer rewrites your public Shopify pages in the tone you pick, then lets you edit any section from a dashboard and A/B test up to four versions of it. Removing the snippet restores your original text.
Why it helps on Shopify
Installing on Shopify
Go to Online Store, then Themes, then Edit code on your live theme.
Open layout/theme.liquid and paste the snippet just before the closing </body> tag.
Save. Later copy changes are made from the dashboard, not the theme editor.
Known limits, stated plainly
The crawler reads the HTML your server sends, so Shopify pages whose text only appears after the browser fetches it are not processed. Because replacement happens in the visitor's browser after the page loads, it is not guaranteed to change what search-engine crawlers index; treat this as a tool for the people reading your site, not as an SEO tactic. A/B results need an analytics tool you already have in place. Only the public editorial pages you select are processed, and you can pause or remove the snippet at any time.
Other stacks
Free during beta