New Proxy Region, Same Saved Market? Test localStorage Preference Priority

The residential exit changes, but a first-party landing page still opens in the market selected yesterday. That can be the intended preference policy rather than a proxy-location failure. Compare the saved preference, the application's selection priority and the rendered result independently. This guide proposes owned-site acceptance tests, not measured 98IP geolocation or browser-compatibility results.

1. Write the market-selection contract first

Ask the site owner what should win: an explicit user selection, an account setting, a route parameter or a network-derived suggestion. There is no universal priority order. Define initial load, explicit selection, reload and a later regional visit separately. A remembered preference is not automatically a defect, and an automatic market suggestion should not silently overwrite an explicit choice unless that is the approved behavior.

For an owned fixture, use a dedicated test key such as qa_market_choice and synthetic values market-a and market-b. Decide what an absent, invalid or unsupported value means. Keep the expected answer outside the mapping being tested, with reviewed market content and a concrete page-ready marker. Do not use the visible country label alone as evidence of actual egress or complete localization.

Scope this procedure to first-party HTTPS pages in a controlled browser profile. Third-party storage restrictions and partitioning, embedded documents and other storage APIs need their own tests. Do not apply a first-party result universally to every browsing mode.

2. Separate storage scope from network scope

Local storage belongs to the document's origin and can persist across browser sessions. Changing the proxy exit does not itself change that origin or clear the stored preference. Compare scheme, host and port; changing from one subdomain to another or from HTTP to HTTPS is not equivalent to keeping the same origin. A same-looking URL path is not sufficient to establish storage identity.

Within the relevant shared local-storage area, another same-origin tab can observe the saved value. That does not mean the application's visible market updates automatically. The application must implement its intended synchronization behavior. Do not confuse localStorage with cookies, sessionStorage, a server-side account preference or a Service Worker response cache.

Use the site's developer tools only in the owned test profile to inspect the dedicated fixture key. Record its presence, synthetic value and the origin being inspected. Never dump the entire storage area, which may contain unrelated identifiers or sensitive application data.

3. Test persistence and cross-tab behavior separately

1. Begin in a controlled profile on the owned HTTPS fixture. Remove only the dedicated test preference key, keeping other approved state fixed. Load through the baseline route and verify the no-preference result against the owner's policy.
2. Use the real market selector to choose market-a. Check the current page's content, stored fixture value and intended output requests. Reload the same origin and verify whether the approved remembered choice survives.
3. Change only the regional proxy route, confirm actual egress and load the same origin with the saved value intact. If the contract gives the explicit choice priority, market-a should remain; that is not evidence that the route failed.
4. Open another first-party tab sharing the same relevant storage area. Change the fixture preference to market-b through the real control in the first tab. Inspect both the stored value and each tab's UI after the defined readiness point.
5. Check the storage-event design precisely: a localStorage change is notified to other eligible same-origin documents, not to the window making that change. The initiating page must update itself through its own application path; do not wait for its own storage event as the only update mechanism.
6. Return to the original selection and repeat the reload and regional visit. Confirm that a failed or interrupted selection does not leave a success toast paired with an old saved value or stale content.

These are expected results until observed. Record the browser build and profile conditions. Do not treat sessionStorage as a drop-in cross-tab equivalent: its storage-event scope is different. If the app intentionally updates other tabs only after reload, test that documented policy rather than demanding immediate synchronization.

4. Include invalid state and unavailable storage

In an isolated fixture, place an unsupported synthetic market value in the dedicated key. The application should follow its approved fallback or correction path rather than crash, select an unauthorized market or silently report success with inconsistent state. If the app stores structured text, include its documented malformed-value case; do not assume every preference is JSON.

Using an owner-approved test setup, exercise a condition where persistence is unavailable or blocked. Accessing localStorage can fail because of a browser policy, and reads or writes need appropriate error handling. Record the actual exception and behavior rather than assuming a private mode always behaves in one specific way.

The owner must decide whether a choice can remain active only for the current page, whether the interface should explain that it was not saved, or whether the operation should be refused. Do not promise persistence when the write failed. A successful in-memory UI update is different from a verified stored preference that survives reload.

Do not clear all browser storage to make these tests pass. That may remove consent, account state and unrelated application data while hiding the precedence bug. Reset only the owned fixture key or use an explicitly disposable test profile; never perform this cleanup in a real customer's session.

5. Diagnose the first disagreement

• Stored value stays old after a selection: inspect the write path, actual origin, policy errors and any later overwrite.
• Storage changes but the initiating page stays old: inspect its local application update; it should not rely solely on receiving its own storage event.
• One tab updates while another remains stale: inspect the approved cross-tab policy, listener lifecycle and the storage area each document actually shares.
• Preference and UI agree but the returned content is old: inspect the requested route, server account preference and response delivery. The separate Service Worker cache acceptance guide handles cached responses.
• A regional visit chooses differently: compare final origin, explicit preferences, account state and application build before assigning the difference to exit geography.

Keep cookies and server-side preferences fixed when isolating local storage. If several mechanisms can supply the market, record their intended precedence and observed values without copying secrets. A proxy cannot decide which client-side preference the application chooses to honor.

Preserve fixture/build ID, browser version, origin, route evidence, dedicated key state, selected market, rendered content markers and each relevant transition. For event diagnostics keep only the synthetic key and values. Do not retain customer storage dumps, authentication tokens, cookies or proxy credentials.

6. Use 98IP to change the route without changing the test question

When authorized localization QA needs residential regional perspectives, consult the 98IP residential proxy product page and API configuration documentation. Use a method supported by the account, keep the session policy stable during each sequence and record actual usage.

A residential route changes a network perspective; it does not erase a first-party preference or guarantee the page will select a particular language, currency or market. Keep the same origin and controlled state when comparing routes, then vary the saved preference as a separate experiment. Limit traffic and use only owned or explicitly authorized fixtures.

• The owner has defined preference priority and a no-preference baseline.
• The inspected origin and relevant storage area are known.
• Current-page update, persistence after reload and cross-tab synchronization are separate assertions.
• The initiating window is not expected to receive its own storage event.
• Invalid values and unavailable persistence have approved visible outcomes.
• Changing an exit is not mistaken for clearing browser or account state.

Should a new country exit reset localStorage? No automatic reset follows from the exit change itself. Verify the application's explicit preference policy.

Does a successful selection prove it was saved? No. Check the test key and reload outcome, including error handling.

Should we delete all storage whenever a market looks wrong? No. Preserve evidence and isolate the owned test key or disposable profile.