Open-source ESP32-C3 DNS ad blocker handles over 500,000 domains without PSRAM

Developer Zed (M-Abozaid) released esp32-c3-adblock, an open-source Pi-hole-style DNS ad blocker running on a $2 ESP32-C3 board without PSRAM. Domains are stored in flash as sorted 40-bit FNV-1a hashes, with lookups taking about 10 ms; ~0.7 MB of flash holds over 140,000 domains using only ~50 KB of RAM.

• Domains stored as 40-bit FNV-1a hashes, 5 bytes each
• 140,000+ domains in ~0.7 MB flash using ~50 KB RAM
• Lookup takes ~10 ms with about 18 flash reads
• Up to 537,000 domains in single-app layout, but no firmware OTA