Does Capacitor HTTP plugin bypass WebView cache consistently across iOS and Android?

Short answer

The Capacitor HTTP plugin does bypass the WebView’s internal cache, but it does not ignore all caching policies. Requests go through the native networking stack (URLSession on iOS, OkHttp on Android), which respects standard HTTP cache headers according to its own caching rules. Therefore, the plugin consistently bypasses the WebView cache, yet it may still cache responses locally if the server permits it, and the exact caching behavior can differ between iOS and Android.

Confirmed facts

• The plugin uses native libraries, not the WebView’s fetch/XHR, so WebView‑stored responses are never consulted.
• Both URLSession and OkHttp obey Cache-Control, Expires, ETag, etc., according to their respective HTTP caching specifications.
• When the server sends Cache-Control: no-cache or no-store, neither native stack stores the response, effectively mimicking a full bypass of any cache layer.
• If the response allows caching (e.g., max-age or Expires in the future), URLSession may store it in its shared cache, while OkHttp may store it in its disk cache; these locations are independent of the WebView cache.

Likely explanation of differences

URLSession’s default caching policy is to store responses that are cacheable unless explicitly told not to, and it shares a single cache per app unless a custom cache is configured. OkHttp, by default, also caches responses that meet HTTP caching criteria, but its cache directory and eviction rules differ from URLSession’s. Consequently, the same server headers can lead to cached responses on one platform but not the other, depending on each stack’s implementation details and the version of the underlying library.

Steps to verify behavior for your app

1. Instrument a test endpoint that returns a JSON payload with a specific Cache-Control header (e.g., no-cache, then later max-age=3600).
2. In the Capacitor app, call CapacitorHttp.get(url) (or the equivalent method) to fetch the endpoint.
3. On iOS, open Xcode’s Network Inspector or use os_signpost logs to confirm that the request hits URLSession and check whether a cached response is used.
4. On Android, open Android Studio Profiler → Network or enable OkHttp logging (HttpLoggingInterceptor) to see if the request is served from OkHttp’s cache.
5. Repeat the same request using the WebView’s fetch API and compare the logs; you should see WebView cache hits/misses only for the fetch calls.

What to check if results differ from expectation

If you observe caching on a platform where you expected none, verify the exact version of the Capacitor HTTP plugin and the underlying OS networking library (e.g., URLSession version tied to iOS SDK, OkHttp version bundled with the plugin). Changes in default caching behavior between plugin releases can affect the outcome.