On behalf of the Developers Alliance, the leading advocate for developers, the companies they build, and the industries that rely on them, we write to express our strong opposition to Assembly Bill 566.
Protecting consumer privacy is extremely important and should be a top priority for developers. However, AB 566 would require browsers to include a universal “opt-out” option, giving users the ability to opt out of data transfers for advertising purposes on all web apps with a single click. This would severely impact the user experience and make it much harder for small web developers to grow and compete.
Data and data-powered digital ads are critical to small developers and their businesses. Basic, anonymous data and user signals are used to perform tasks that enhance the user experience, such as keeping people logged in, storing preferences, recommending content, or displaying ads. In 2024 alone, U.S. digital advertising revenue reached a record $258.6 billion, demonstrating just how vital ad-supported business models are to the broader developer ecosystem.
Opt-outs are rarely understood, and their impacts on developers can have profound effects. When Apple launched its App Tracking Transparency (ATT) feature in 2022, a feature that sounded like a step towards transparency and empowering user control over data, it significantly impacted small developers and businesses that use data-driven digital advertising. ATT presents users with a misleading choice: “Allow” or “Ask App Not to Track.” Without more information on use, many users reflexively pick “Ask App Not to Track.”
The results of ATT have been a massive decrease in data for advertising purposes, impacting apps that primarily generate revenue from ads. Less data means less effective ads, as studies show that ATT has caused a 37 percent decrease in ad-generated revenue for businesses using data-powered online ads. Regulators in France even fined Apple $162 million over the practice, arguing that it harms small publishers and “is neither necessary for nor proportionate with” Apple’s goal of protecting personal data. Requiring a similar, blanket opt-out that would be poorly understood by users and applying it to all browsers could have catastrophic consequences for the digital ecosystem.
In addition, AB 566 not only strips web developers of the essential tools they need to personalize, fund, and improve their innovations, but it would also burden them with the massive technical and financial challenge of handling, storing, and managing millions of new opt-out signals. With existing privacy compliance costs already piling up, including an estimated $55 billion in total compliance costs from the CCPA, which impacts 75 percent of California businesses, forcing developers to handle a parallel stream of additional opt-out signals would only increase these figures and make it even harder for them to compete.
We acknowledge the importance of privacy protection, but a one-size-fits-all opt-out is not the right approach. We strongly oppose AB 566 in its current form and instead urge protecting consumers’ privacy the right way—by targeting bad actors and not punishing honest developers who are working to build a safer, more open, and affordable internet for everyone.
Sincerely,
Jake Ward
Chair, Developers Alliance
