GoKawiilOpen-source project runs 141,000-domain ad-blocker on $2 ESP32-C3 chip
A developer has published an open-source DNS ad-blocking project that runs on the ESP32-C3, a roughly $2 microcontroller, without requiring PSRAM. Instead of storing blocklist domains as strings in RAM, the system stores them as sorted 40-bit hashes in flash memory, allowing over 140,000 domains to fit in about 0.7MB of flash and be matched via binary search in roughly 10 milliseconds using only about 50KB of RAM.
GoKawiil's interpretation of the reporting above, not reported fact.
The approach could make Pi-hole-style ad-blocking accessible on far cheaper hardware than typical ESP32 PSRAM-equipped boards, which the project says cost around $8. The technique also scales to larger chips, with the author claiming a 16MB ESP32-S3 could hold roughly 2.7 million hashed domains versus about 466,000 using strings in PSRAM, suggesting the method could become a more efficient default for embedded DNS filtering generally.
- The project stores blocklist domains as 40-bit hashes in flash rather than full strings in RAM.
- It supports 140,000+ domains using about 0.7MB flash and 50KB RAM, with lookups taking roughly 10ms.
- The technique also scales to larger chips like the ESP32-S3, potentially supporting millions of domains.
ESP32-C3 DevKitM-1 Development Board — This is exactly the kind of low-cost board the project is built around — an inexpensive ESP32-C3 with no PSRAM needed to run this clever flash-based DNS ad-blocker. It's a great way to actually try out the hash-table sinkhole trick yourself and turn a $2 chip into a tiny Pi-hole replacement.
See ESP32-C3 DevKitM-1 Development Board on Amazon → Affiliate link — we may earn a commission on purchases, at no extra cost to you. Product picked by AI based on this article; it is not a tested recommendation.Source: github.com, 2026-10-07
Published there as: “ESP32-C3 Adblock”
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