Closing a Critical Internet Privacy Gap for Billions of Users: Android 17 Rolls Out ECH Support

When you launch an app or visit a website, you likely assume your connection is private. In reality, a critical privacy gap remains. Even when your traffic is encrypted using secure HTTP (HTTPS), the domain names of every website or service you connect to are exposed in plain text to Internet Service Providers (ISPs), Wi-Fi operators, and malicious actors alike.

In the modern digital era of data harvesting and automated profiling, this unencrypted metadata can be stitched together into surprisingly revealing profiles. A 2021 Federal Trade Commission (FTC) report revealed that major internet service providers (ISPs) continuously monitor unencrypted domain and browsing metadata, monetizing sensitive user categories such as location, demographics, and political affiliation with targeted advertising. Beyond commercial profiling, exposed domains can enable targeted scams, network censorship, and digital surveillance.

Closing this privacy gap makes the internet safer for everyone. In fact, it's not just one gap: domain data leaks in two places during every connection — the initial DNS lookup and the unencrypted ClientHello in the Transport Layer Security (TLS) handshake. In 2018, Jigsaw partnered to help Android introduce DNS-over-TLS support in Android 9 (P). As encrypted DNS has gained significant momentum — now protecting over 25% of global web traffic — Jigsaw has again teamed up with Android to address the second critical leak: the TLS ClientHello.

A Blueprint for the Industry

Encrypted ClientHello (ECH) is a new internet standard published earlier this year that is designed to close this privacy gap. It hides the domain name using a secret encryption key that only the destination website can unscramble. Critically, though, not all web servers will offer ECH support. To avoid exposing only certain connections as ECH-protected, apps and browsers should use ECH GREASE — which sends fake, randomized ECH extensions to sites that don't support ECH — so that every connection request looks the same.

Starting with Android 17, ECH GREASE will be enabled by default — opening the door to an industry-wide rollout of robust domain privacy to billions of mobile users worldwide. Android 17 sets a landmark precedent as the first major mobile OS to enable broad ECH support. To help app developers leverage this new capability, OkHttp, the open-source HTTP client powering millions of Android apps, has integrated ECH support into its core library.

Deploying a core networking upgrade across billions of devices requires confidence that the changes will not cause significant connection failures. To validate Android's intended approach, Jigsaw empirically measured ECH performance at scale — showing how it can operate safely without breaking connectivity or slowing down connections.

Together, Android, OkHttp, and Jigsaw are proud to contribute to the industry's shared momentum toward a more private web.

Ecosystem-Wide Support for ECH

Achieving lasting internet privacy requires alignment across operating systems, networking libraries, and applications. Leaders across the ecosystem have voiced strong support for bringing ECH into the mainstream:

"Enabling ECH by default across Android and major network libraries is a crucial step forward for user protection. We're excited to see Android take this step and encourage developers to drive adoption across the entire ecosystem." — Ehren Kret, CTO, Signal

"With OkHttp we strive to build network infrastructure that's secure, efficient, and reliable. We were excited to integrate ECH because it improves user privacy." — Jesse Wilson, OkHttp project lead

"Internet security must evolve continuously to match modern threats. Jigsaw's ECH measurements helped validate deployment in Android 17, addressing a long-standing vulnerability and advancing our shared goal of a more private web." — David Kleidermacher, VP of Engineering, Android Security & Privacy

"ECH support for Android is a huge step towards closing one of the largest remaining structural privacy holes left on the Internet." — Nick Sullivan, Co-author of the ECH standard and Founder of Cryptography Consulting LLC (formerly Head of Research at Cloudflare)

Validating ECH Readiness at Global Scale

Before enabling ECH in the platform, the Android team needed empirical answers to three critical questions:

1. Does ECH impact performance?
2. Does ECH increase connection failures?
3. Do any ISPs or middleboxes around the world already block ECH traffic?

We previously published research on the performance of the first step in an ECH connection, the retrieval of connection configuration information over DNS. Building on this foundation, Jigsaw conducted global measurements to evaluate real-world outcomes and illustrated that ECH can be deployed without impact to server incompatibility or ISP interference.

Connection Success

To measure server resilience, Jigsaw tested ECH GREASE connections against the top 10,000 web domains globally. Our GREASE Compatibility Report revealed zero change in connection success rates compared to baseline TLS requests, demonstrating that modern servers handle ECH extensions without breaking.

Global Network Readiness

To understand current network behavior, Jigsaw evaluated HTTP requests across 202 unique countries and 740 unique ISPs, including heavily filtered environments. Our Multi-Country ISP Analysis demonstrated a virtually 0% network interference rate globally. Even in heavily restricted nation-wide networks like Russia's and China's, ECH GREASE requests maintained parity with baseline connections — indicating that intermediate middleboxes are not blocking the protocol.

While ECH protects user privacy by encrypting domain names from middlebox inspection, we recognize that managed networks — such as schools and enterprises — rely on network controls to enforce safety policies and block malware. To support these environments, Android provides administrative controls allowing network operators to manage ECH behavior via DNS, ensuring local network governance remains intact without compromising baseline privacy on the open web.

Open-Source Measurement Tooling & Data

We encourage developers to visit our repository on GitHub to review the reports, inspect the full global datasets, and utilize the interactive Jupyter notebooks to run your own custom ECH measurements. If you do, post on our GitHub discussion board to let us know how they helped you build the confidence to adopt ECH on your own services!

Paving the Way for a Confidential Internet

A confidential, secure, and open web is fully achievable when privacy and network performance are treated as complementary forces rather than trade-offs. By combining empirical testing with ecosystem collaboration, Android, OkHttp, and Jigsaw are demonstrating that modern privacy protocols can deploy at global scale without sacrificing speed or reliability.

We invite developers, platform operators, and security advocates to partner with us:

• Adopt Modern Networking Libraries & Best Practices: App developers should upgrade to OkHttp 5.5.0 and enable ECH. Developers building or configuring network stacks should also consult our technical recommendations on GitHub for optimizing HTTPS RR queries for the best performance.
• Evaluate Performance with Open-Source Tools: Explore Jigsaw's open-source measurement tools on GitHub to test your own domain configurations and evaluate how your services perform with ECH enabled.
• Collaborate on Standards: Join us in advocating for ECH to be enabled by default across all major operating systems, networking stacks, and server infrastructure — ask your hosting providers to enable ECH support for your domains too!

When privacy is built into the core foundation of the internet, we protect not just network traffic, but the agency and safety of users everywhere.

By Maddy Hoffman, Senior Product Manager, Jigsaw