DNS

Hand holding the ESP32-C3 ad blocker board in a USB adapter
Open-Source ESP32-C3 DNS Ad Blocker Holds Up to 537,000 Domains Without PSRAM
DIY Electronics ESP32
The esp32-c3-adblock project stores blocklists as 40-bit hashes in flash, fitting 140,000-plus domains in 0.7 MB on a $2 ESP32-C3 with about 50 KB of RAM.