By: thunderbiscuit (@thunderB__)

Recorded July 23, 2026 at bitcoin++ Toronto, consensus edition — Toronto, Canada.

Most discussions of Compact Block Filters focus on the protocol. This talk focuses on the users, and what wallet devs can expect if they are considering integrating Compact Block Filter syncing into their mobile/server applications.

This talk covers the day-to-day reality of CBF-backed mobile wallets, mostly in comparison to standard-in-the-industry Electrum/Esplora setups. Storage footprint (~30–70 MB of chain data), bandwidth costs (~100 MB for months of history, more for wallet recovery), sync behaviour (minutes on WiFi for a yearly gap, seconds for daily use), and how background sync can make this nearly invisible to users. I will also be cover the tradeoffs, i.e. no mempool visibility and how unconfirmed transactions require user education, and fee estimation.

The second half of the talk focuses on how to ship this today using BDK and the Kyoto light client. I'll look at what integration looks like, what decisions developers need to make, and what your users gain in terms of privacy and reduced infrastructure dependency.

If you're building a Bitcoin mobile wallet and wondering whether CBF is ready for production or what your users can expect if you enable this type of syncing, this talk is for you!