Hardware & Devices · 2 min read · 19 July 2026

ESP32 Ad-Blocking Dongle Fits 537,000 Domains in 50KB of RAM

A $5 microcontroller demonstrates efficient DNS filtering at scale using compression techniques that reduce memory footprint by 99%.

Abstract illustration representing data compression and efficient memory use — AI-generated illustration · Sylvaris

Compression Achievement

A developer has successfully compressed over half a million ad-blocking domain entries into approximately 50KB of RAM on an ESP32 microcontroller. The firmware can respond to blocked DNS lookups in roughly 10 milliseconds, making it practical for real-time network filtering.

The project demonstrates that sophisticated ad-blocking can run on inexpensive hardware costing around $5. Traditional ad-blocking solutions typically require significantly more memory and processing power.

Technical Implementation

The ESP32-based device functions as a DNS filter, intercepting domain lookups and blocking requests to known advertising and tracking domains. The extreme compression allows the entire blocklist to fit within the microcontroller's limited RAM while maintaining fast lookup speeds.

This approach represents a hardware-based alternative to software ad-blockers running on computers or routers. The low cost and minimal power requirements make it suitable for always-on network filtering.

sources

https://www.tomshardware.com/networking/clever-hacker-fits-537-000-domains-in-a-tiny-usd5-esp32-ad-blocking-dongle-firmware-uses-only-around-50kb-of-ram-and-can-answer-blocked-lookups-in-10-milliseconds

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