How does he work?

[vaynevayne]

When I changed the value, I found that the url had not changed, but when the page was refreshed, the value was still there, and neither session nor local strorage saw it.
Excuse me, where is the value stored?

[nitedani]

The values are stored in the address bar as a query parameter. When you change a value in the store, then it should change the url in the address bar only if that specific value is selected to be persisted for the page (select option).

For example - if your select looks like select(pathname) { return { count: "/items" === pathname }} then the middleware will only work on that single /items page, storing the count in the url. If you go to /apples page, then the middleware won't load count from the url.
You can try returning something like { count: true } in select and see if it fixes the issue.

If it still doesn't work and you would like me to fix the issue, please create a reproduction on stackblitz/post your store configuration.
You can create a reproduction based on this one: https://stackblitz.com/github/nitedani/zustand-querystring/tree/main/examples/react