Does Swagger UI retain the selected server across page reloads in embedded deployments?

Question

When an OpenAPI 3.x document defines multiple servers entries, Swagger UI renders them as a dropdown for "Try it out" requests. The first entry in the array is selected by default, yet the behavior after a user changes that selection and reloads the page varies across releases and embedding contexts.
Recent standalone Swagger UI distributions appear to persist the active server in browser local storage, whereas older versions or instances embedded in host applications with restricted storage may reset to the first entry on every load. Because local-storage access is not guaranteed in private browsing modes or sandboxed iframes, teams should verify persistence against the exact version bundled in their application rather than relying on general documentation.
Does the selected server survive a page reload in a given Swagger UI version, and what configuration or deployment factors determine whether local-storage persistence is available? Which behavior should teams expect when the same document is rendered in both a standalone distribution and an embedded iframe?

Tasadduq Burney · Answer

Does Swagger UI retain the selected server after a page reload?
It depends on the deployment context. Swagger UI restores the user's server choice only when it can read and write localStorage under the current origin. In a same-origin standalone page or embedded iframe, the selection usually survives a reload. In a cross-origin iframe, private-browsing window, or sandboxed iframe without storage access, the UI falls back to the first servers entry.
Confirmed factors

OpenAPI 3.x servers entries render as a dropdown; the first entry is the default.
Persistence relies on browser localStorage, not server-side state or URL query parameters.
Same-origin iframes share the host origin's storage; cross-origin iframes typically have isolated or partitioned storage.
Sandbox attributes such as allow-same-origin affect whether the iframe can access localStorage.
Private or incognito sessions may clear storage when the tab closes, so persistence can be temporary.

Version assumption
Newer Swagger UI releases (approximately v4.15 and later) write the selected server index or URL to localStorage. Older releases may keep the choice in memory only and reset on reload. Treat the exact version as unverified until you check the bundled package.json.
Verification steps

Open the Swagger UI page in the exact embedding context you use.
Select a non-default server from the dropdown.
Open DevTools, go to Application > Local Storage, and look for a key such as swagger-ui:serverIndex or swagger-ui:serverUrl.
Reload the page. If the key remains and the dropdown shows your selection, persistence works.
Repeat in a private window or sandboxed iframe; if the key is missing or the console shows a storage error, expect a reset to the first server.

Missing diagnostic detail
Provide the exact Swagger UI version bundled in your application. The persistence logic changed between releases, and the version determines whether built-in localStorage persistence exists at all.

Does Swagger UI retain the selected server across page reloads in embedded deployments?

1 answer

Does Swagger UI retain the selected server after a page reload?

Confirmed factors

Version assumption

Verification steps

Missing diagnostic detail

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