Please, Stop Redirecting to Login on 401 Errors 🛑

You spend 15 minutes filling out a long configuration form. You get a Slack notification, switch tabs, reply to a colleague, and grab a coffee.

30 minutes later, you come back to the form and click "Save".

The page flashes. The login screen appears.And your data is gone.

This is the most annoying UX pattern in web development, and we need to stop doing it.

The "Lazy" Pattern

Why does this happen? Usually, it's because the JWT (access token) expired, the backend returned a 401 Unauthorized, and the frontend code did exactly what the tutorials said to do:

// Don't do this
axios.interceptors.response.use(null, error => {
  if (error.response.status === 401) {
    window.location.href = '/login'; // RIP data 💀
  }
  return Promise.reject(error);
});

Developers often argue: "But it's a security requirement! The session is dead!"

Yes, the session is dead. But that doesn't mean you have to kill the current page state.

The Better Way (Resilience)

If a user is just reading a dashboard, a redirect is fine. But if they have unsaved input (forms, comments, settings), a redirect is a bug.

Here is how a robust app handles this:

1. Intercept: Catch the 401 error.

2. Queue: Pause the failed request. Do not reload the page.

3. Refresh: Try to get a new token in the background (using a refresh token) OR show a modal asking for the password again.

4. Retry: Once authenticated, replay the original request with the new token.

The user doesn't even notice. The form saves successfully.

How to test this? (The hard part)

Implementing the "Silent Refresh" is tricky, but testing it is annoying.

Access tokens usually last 1 hour. You can't ask your QA team to "wait 60 minutes and then click Save" to verify the fix.

You need a way to trigger a 401 error exactly when you click the button, even if the token is valid.

The "Chaos" Approach

Instead of waiting for the token to expire naturally, we can just delete it "mid-flight."

I use Playwright for this. We can intercept the outgoing request and strip the Authorization header before it hits the server.

This forces the backend to reject the request, triggering your app's recovery logic immediately.

Here is a Python/Playwright snippet I use to verify my apps are "expiry-proof":

def test_chaos_silent_logout(page):
    # 1. Login and go to a form
    page.goto("/login")
    # ... perform login logic ...
    page.goto("/settings/profile")

    # 2. Fill out data
    page.fill("#bio", "Important text I don't want to lose.")

    # 3. CHAOS: Intercept the 'save' request
    def kill_token(route):
        headers = route.request.headers
        # We manually delete the token to simulate expiration
        if "authorization" in headers:
            del headers["authorization"]

        # Send the "naked" request. Backend will throw 401.
        route.continue_(headers=headers)

    # Attach the interceptor
    page.route("**/api/profile/save", kill_token)

    # 4. Click Save
    page.click("#save-btn")

    # 5. Check if we survived

    # If the app is bad, we are now on /login
    # if page.url == "/login": fail()

    # If the app is good, it refreshed the token and retried.
    # The text should still be there, and the save should succeed.
    expect(page.locator("#bio")).to_have_value("Important text I don't want to lose.")
    expect(page.locator(".success-message")).to_be_visible()

Summary

Network failures and expired tokens are facts of life. Your app should handle them without punishing the user.

If you want to build high-quality software, treat 401 Unauthorized as a recoverable error, not a fatal crash.

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PS: If you need to test this on real mobile devices where you can't run Playwright scripts, you can use a Chaos Proxy to strip headers on the network level.