The Web's Identity Crisis: Understanding the Effectiveness of Website Identity Indicators


Christopher Thompson, Martin Shelton, Emily Stark, Maximilian Walker, Emily Schechter, and Adrienne Porter Felt, Google


Users must understand the identity of the website that they are visiting in order to make trust decisions. Web browsers indicate website identity via URLs and HTTPS certificates, but users must understand and act on these indicators for them to be effective. In this paper, we explore how browser identity indicators affect user behavior and understanding. First, we present a large-scale field experiment measuring the effects of the HTTPS Extended Validation (EV) certificate UI on user behavior. Our experiment is many orders of magnitude larger than any prior study of EV indicators, and it is the first to examine the EV indicator in a naturalistic scenario. We find that most metrics of user behavior are unaffected by its removal, providing evidence that the EV indicator adds little value in its current form. Second, we conduct three experimental design surveys to understand how users perceive UI variations in identity indicators for login pages, looking at EV UI in Chrome and Safari and URL formatting designs in Chrome. In 14 iterations on browsers' EV and URL formats, no intervention significantly impacted users' understanding of the security or identity of login pages. Informed by our experimental results, we provide recommendations to build more effective website identity mechanisms.

USENIX Security '19 Open Access Videos Sponsored by
King Abdullah University of Science and Technology (KAUST)

Open Access Media

USENIX is committed to Open Access to the research presented at our events. Papers and proceedings are freely available to everyone once the event begins. Any video, audio, and/or slides that are posted after the event are also free and open to everyone. Support USENIX and our commitment to Open Access.

@inproceedings {236318,
author = {Christopher Thompson and Martin Shelton and Emily Stark and Maximilian Walker and Emily Schechter and Adrienne Porter Felt},
title = {The Web{\textquoteright}s Identity Crisis: Understanding the Effectiveness of Website Identity Indicators},
booktitle = {28th USENIX Security Symposium (USENIX Security 19)},
year = {2019},
isbn = {978-1-939133-06-9},
address = {Santa Clara, CA},
pages = {1715--1732},
url = {},
publisher = {USENIX Association},
month = aug,

Presentation Video