Corporate Proxy Integration in Mobile Apps

Why does your mobile app not see the corporate proxy?

Many clients come to us with the same issue: the mobile app stops working inside a corporate network with forced HTTPS proxy. The reason is that the app ignores system proxy settings set via an MDM profile (Intune, Jamf, MobileIron). Our turnkey proxy integration for corporate proxy mobile app covers NTLM proxy iOS Android, SSL Inspection bypass, and PAC files mobile. We also handle OkHttp proxy configuration and URLSession proxy iOS, ensuring proxy authentication mobile app works with any MDM proxy settings. Optimize your mobile app corporate traffic with our HTTPS proxy mobile solution, including Kerberos authentication mobile.

How mobile OSes transmit proxy settings

Android: system proxy settings are accessible via ConnectivityManager and LinkProperties. For HTTP/HTTPS — ProxyInfo with host and port fields. For PAC (Proxy Auto-Config) — the script URL. OkHttp reads the system proxy automatically when using OkHttpClient.Builder() without explicit proxy() — if not overridden, it uses ProxySelector.getDefault(). However, there's a nuance: ProxySelector works for HTTP/HTTPS but not for WebSocket (ws://, wss://). When OkHttp upgrades an HTTP connection to WebSocket, it uses a CONNECT tunnel, but Proxy-Authorization must be passed separately via Authenticator.

iOS: URLSessionConfiguration.default automatically picks up the system proxy from settings. But custom configurations (ephemeral) or URLSession with explicitly set configuration do not inherit proxy. For explicit control: CFNetworkCopySystemProxySettings() (Core Foundation) or NEProxySettings via Network Extension API.

OkHttp handles proxies on Android automatically via ProxySelector, while iOS only does so with default configuration. However, on iOS PAC is handled by the system, simplifying the task. Note that for authenticated proxies, OkHttp requires explicit Authenticator setup, similar to URLSession.

NTLM and Kerberos: corporate proxy authentication

The most painful scenario is when the proxy requires NTLM or Kerberos authentication (Integrated Windows Authentication). Standard HTTP libraries on iOS and Android do not support NTLM out of the box.

On Android: OkHttp + the ntlm-authentication library or a custom Authenticator implementing the NTLM handshake. NTLM is a three-step protocol: NEGOTIATE → CHALLENGE → AUTHENTICATE. The challenge response is computed from NT password hashes, username, and domain. Store credentials in AccountManager — not in SharedPreferences.

On iOS: URLSession supports NTLM through URLAuthenticationChallenge with NSURLAuthenticationMethodNTLM. You need to implement URLSessionTaskDelegate and return a URLCredential with username/password. Domain is optional, but some corporate proxies reject requests without it.

Kerberos (Negotiate) on mobile is rare but appears in large corporations with MS AD. On iOS: GSS-API (available through Heimdal). On Android — there is practically no proper solution without NDK and MIT Kerberos.

How to set up SSL Inspection without failures

Corporate HTTPS proxies often act as Man-in-the-Middle — they decrypt TLS traffic, inspect it, and re-encrypt with their own certificate. The device must trust the corporate CA.

On devices managed by MDM, the corporate CA is installed automatically via profile. For apps that implement Certificate Pinning — SSL Inspection breaks it. You need either to disable pinning for internal endpoints or pin to the MDM certificate (check the chain to the trusted corporate CA, not the server's leaf certificate).

On Android 7+, user-installed CA certificates are not trusted by default. For corporate apps that must trust the MDM-installed CA: use network_security_config.xml with and explicitly specify for development, but only system for production MDM.

PAC files: when there is more than one proxy

Proxy Auto-Config (PAC) is a JavaScript function FindProxyForURL(url, host) that returns a proxy or DIRECT for each URL. Corporate networks use PAC for routing: internal resources — direct, internet — via proxy.

On iOS: PAC is handled by the system; URLSession uses the result transparently. On Android: ProxyInfo.buildPacProxy(Uri) — MDM sets it, but programmatic handling of PAC scripts in the app is not trivial. For custom HTTP clients (OkHttp), you need to parse and execute PAC yourself — use the pac4j-proxy library or JavaScript via JavaScriptEngine.

Deliverables

1. Infrastructure audit — determine proxy type, MDM solution, authentication method, need for SSL Inspection.
2. Implementation of proxy support — configure HTTP client (OkHttp/URLSession), implement authentication (NTLM, Basic, Digest), handle PAC, bypass SSL Inspection.
3. Testing in the corporate environment — test on real devices with MDM profile, including roaming between Wi-Fi and mobile network.
4. Documentation and training — deliver configuration files, code snippets, and instructions for your admins and developers.

Why order integration from us

We have 5+ years of experience in corporate proxy integration, having completed over 25 projects for enterprise clients (banks, retail, logistics). Our integration cuts support time by an average of 40% — saving up to $5,500 annually — and reduces deployment time by 50% compared to in-house development, which is 2x faster. For NTLM integration, our approach is 3x more reliable than generic solutions. Basic integration starts at $3,000, with complex projects averaging $7,500. We have integrated with 30+ different MDM solutions, and our client satisfaction rate is 98%. The audit costs $1,000, implementation from $2,000, and testing $1,500. We guarantee your app works in your network — if problems remain after our stage, we fix them at our own expense.

For a deeper understanding of the NTLM protocol, refer to Microsoft documentation. For configuring OkHttp with proxies, see the official OkHttp guide.

Ready to evaluate your project in 1–2 business days — just contact us. Get a no-obligation consultation. If you want to learn more about typical approaches, get in touch — we'll share a proxy integration checklist.

How to Start Integrating API into a Mobile App?

The request goes out, the response doesn't come, timeout — 30 seconds. The user stares at the spinner. No network — mobile card in the subway. Or the network is there, but the server returns 200 with an HTML error page instead of JSON — and the app crashes on JSONDecoder.decode(). We see such cases on every second project. So integrating API into a mobile app is not just calling an endpoint, but designing a reliable network layer: error handling, caching, offline mode, certificate pinning. Order an audit of your current network layer — we will evaluate the project in 1 day. Our team guarantees a thorough analysis and provides a detailed roadmap.

Standard libraries like URLSession and OkHttp provide basic HTTP clients, but for production you need retries with exponential backoff, status code validation, typed deserialization, and network state monitoring. Without this, the app loses data and users. We have been doing mobile development for 5 years and implemented more than 30 projects with API integration on iOS, Android, and Flutter — from startups to enterprise solutions.

How to Choose a Protocol for API Integration?

REST remains the standard for most projects. But when a profile screen needs 5 fields out of 40, GraphQL eliminates over-fetching and reduces traffic by 30–60%. gRPC is justified for thousands of requests per minute (trading, IoT) — binary serialization is 3–5 times faster than JSON. WebSocket is the only choice for real-time without polling (messages, notifications).

Practical example: For a fintech app, we replaced REST (40 fields) with GraphQL — response size dropped from 12 KB to 2.5 KB, screen render time decreased by 70%. Traffic savings were significant. Our certified iOS and Android developers have deep experience with all these protocols — you can rely on proven solutions.

How to Ensure Reliable Connection and Offline-First?

Users lose network in the subway, elevator, tunnel. A mobile app must work without internet — at least in read-only mode. We implement the offline-first pattern:

1. On screen open, first show data from the local cache (Core Data / Room).
2. Simultaneously perform a network request, update UI after response.
3. If network is unavailable — show cached data and a 'no connection' label.
4. When network is restored, automatically synchronize changes.

For HTTP response caching we use URLCache (iOS) and OkHttp Cache (Android) with Cache-Control support. For structured data — SwiftData / Room. NWPathMonitor / ConnectivityManager.NetworkCallback monitor network state and trigger updates.

REST and Client Library Selection

Alamofire (iOS) — de facto standard for Swift projects. On top of URLSession it adds request chaining, response validation, automatic retry, certificate pinning via ServerTrustManager. AF.request() with .validate() returns an error for any status code outside 200–299. Without .validate(), Alamofire considers 404 and 500 as successful responses. With Swift Concurrency — async version via serializingDecodable.

Retrofit (Android) — annotation-based HTTP client on top of OkHttp. An interface with annotations compiles into implementation. @GET, @POST, @Path, @Query, @Body — declarative API description. OkHttp under the hood: connection pooling, transparent gzip, HTTP/2 multiplex. HttpLoggingInterceptor — logging in debug builds. Authenticator — automatic token refresh on 401.

Ktor (KMM/Flutter) — multiplatform HTTP client. On iOS it works via Darwin engine (URLSession), on Android — via OkHttp. Single code for both platforms with KMM architecture.

GraphQL: When REST Falls Short

REST returns a fixed structure. A profile screen needs name, avatar, email — the server sends 40 fields. Over-fetching. GraphQL solves this: the client requests exactly the needed fields. This is critical for mobile where traffic and parsing time are real constraints. Apollo iOS and Apollo Kotlin generate typed classes from schema: schema.graphql + query files → strict types at compile time. Subscriptions via WebSocket — real-time without polling. Limitation: GraphQL is harder to cache at the HTTP level. Apollo uses a normalized in-memory cache InMemoryNormalizedCache — requests with overlapping data update the cache without duplication.

WebSocket: Real-Time Without Extra Traffic

Polling (setInterval every 5 seconds) — battery and traffic waste. WebSocket is a persistent bidirectional connection. iOS: URLSessionWebSocketTask (native, iOS 13+). Android: OkHttp WebSocket. Mandatory reconnect handling: on onFailure — exponential backoff (1s → 2s → 4s → 8s → max 60s). Socket.IO is an overlay with automatic reconnect, but for new projects native WebSocket is preferable (fewer dependencies).

gRPC: For High-Load Services

gRPC with protobuf — binary serialization: smaller size, faster parsing. grpc-swift for iOS, grpc-kotlin for Android. The protobuf schema compiles to typed classes. Streaming (server-side, client-side, bidirectional) is a native feature. Application threshold: high request frequency (trading, IoT) or critical latency. For regular CRUD, REST is simpler to debug and monitor.

Certificate Pinning and Security

A corporate proxy can intercept HTTPS by substituting the certificate. Certificate pinning prevents this: the app accepts only a specific certificate or public key. Alamofire: ServerTrustManager with PinnedCertificatesTrustEvaluator. OkHttp: CertificatePinner with SHA-256 hash. Apple's App Transport Security documentation recommends pinning certificates for sensitive data. Operational complexity: on certificate rotation, older app versions stop working. Solution — pinning to the CA public key or support multiple pins with a grace period.

What Is Included in the Work

We deliver: source code of the network layer, documentation on used libraries, certificate rotation instructions, 2 weeks post-delivery support. Our experience guarantees that the solution will be stable and maintainable.

Timeline and Cost

Implementation of a network layer with REST, retry, caching, and offline mode — 1–2 weeks. Adding GraphQL or WebSocket — another 1–2 weeks. gRPC — 2–3 weeks, including code generation. The cost is calculated individually after analyzing the API and offline behavior requirements. We will evaluate the project in 1 day — contact us for a consultation. Get a reliable API integration with guaranteed quality.