ECH Deployment
Encrypted Client Hello (ECH, RFC 9849) encrypts the TLS ClientHello. This protects sensitive information that would otherwise be sent in plaintext, such as the domain name a web browser accesses. How ECH works
We regularly measure ECH deployment by testing the ECH capabilities of domains on the latest CrUX top million list. Our new method solicits ECH configurations by sending ECH requests the server cannot decrypt. Standard-compliant servers must send a valid ECH configuration in response. This detects ECH-capable servers even if they do not publish an ECH configuration in DNS.
Aggregation and Data Filter
Domains With ECH Enabled
latest measurementCounted are domains that completed a TLS handshake with ECH in our measurement, split by whether they publish their ECH configuration in DNS.
ECH Adoption over Time
By ECH Public Name ⓘ A domain is counted under every public name it completed an ECH handshake under, so the bars can add up to more than the total. This happens when a domain uses more than one provider, for example a different CDN for TCP and for QUIC, when its HTTPS record lists configurations with different public names, or, for second-level domains, when its subdomains use different providers.
Example Domain Timeline
More
Discovering Encrypted Client Hello Deployments by Active ECH Probing
Abstract. We present a new measurement method to detect ECH deployments. This method leverages standard-compliant behavior of ECH servers. Prior measurements relied on DNS exposure and reported only one major ECH deployment (Cloudflare). Our measurements reveal yet undiscovered ECH deployments, including a large deployment at Meta. Meta servers support ECH, but ECH configuration is not exposed via the DNS. We also empirically study details such as the level of privacy improvement and latency impact of ECH.
If you use data or tools, please cite our paper:
Jonas Mücke, Konstantin Gasser, Thomas C. Schmidt, and Matthias Wählisch. 2026. Discovering Encrypted Client Hello Deployments by Active ECH Probing. In Proceedings of the 2026 ACM Internet Measurement Conference (IMC '26). ACM, New York, NY, USA, 276–286. https://doi.org/10.1145/3777912.3839832
@inproceedings{10.1145/3777912.3839832,
author = {M{\"u}cke, Jonas and Gasser, Konstantin and Schmidt, Thomas C. and W{\"a}hlisch, Matthias},
title = {Discovering Encrypted Client Hello Deployments by Active ECH Probing},
year = {2026},
isbn = {9798400723278},
publisher = {ACM},
address = {New York, NY, USA},
url = {https://doi.org/10.1145/3777912.3839832},
doi = {10.1145/3777912.3839832},
abstract = {We present a new measurement method to detect ECH deployments. This method leverages standard-compliant behavior of ECH servers. Prior measurements relied on DNS exposure and reported only one major ECH deployment (Cloudflare). Our measurements reveal yet undiscovered ECH deployments, including a large deployment at Meta. Meta servers support ECH, but ECH configuration is not exposed via the DNS. We also empirically study details such as the level of privacy improvement and latency impact of ECH.},
booktitle = {Proceedings of the 2026 ACM Internet Measurement Conference},
pages = {276–286},
numpages = {11},
keywords = {ECH, TLS, HTTPS, DNS, privacy, hypergiant deployment},
location = {Karlsruhe, Germany},
series = {IMC '26}
}
Differences from Our Paper
In our paper, we aggregate multiple toplists. For this website, we only consider the most recent entries of the CrUX top million. Consequently, this analysis shows fewer ECH-capable domains. In addition, all measurements on this website run from a single vantage point at TU Dresden.
echtool
We built echtool to allow full control over ECH handshakes. This includes modifying received ECH configurations and the ClientHelloOuter, and measuring key and configuration grace periods.
It uses the same method as our measurements and supports TCP and QUIC.
The echtool CLI is available for Linux, macOS and Windows. echtool is also available as a web version.
We are open to contributions and new ideas!