{"id":927,"date":"2026-10-07T04:01:36","date_gmt":"2026-10-07T04:01:36","guid":{"rendered":"https:\/\/networkyy.com\/esp32-network-adblock-dns-filtering\/"},"modified":"2026-10-07T04:01:36","modified_gmt":"2026-10-07T04:01:36","slug":"esp32-network-adblock-dns-filtering","status":"publish","type":"post","link":"https:\/\/networkyy.com\/fr\/esp32-network-adblock-dns-filtering\/","title":{"rendered":"Building Network-Level Ad Blocking with ESP32 Microcontrollers"},"content":{"rendered":"<figure><img decoding=\"async\" src=\"https:\/\/images.pexels.com\/photos\/35652454\/pexels-photo-35652454.jpeg?auto=compress&#038;cs=tinysrgb&#038;dpr=2&#038;h=650&#038;w=940\" alt=\"Building Network-Level Ad Blocking with ESP32 Microcontrollers\" style=\"width:100%;height:auto;border-radius:8px;margin-bottom:24px;\" \/><figcaption>Photo by Tanha Tamanna  Syed on Pexels<\/figcaption><\/figure>\n<h1>Building Network-Level Ad Blocking with ESP32 Microcontrollers<\/h1>\n<p>A fascinating project just hit the top of Hacker News: an ESP32-C3-based ad blocking solution that runs entirely on a $5 microcontroller. While Pi-hole has dominated the network-level ad blocking space for years, this lean approach demonstrates something every IT professional should understand\u2014you don&#8217;t need a full Linux stack to perform sophisticated DNS filtering. The ESP32-C3 Adblock project proves that embedded systems can handle real network infrastructure tasks with minimal power draw and maximum efficiency.<\/p>\n<p>This isn&#8217;t just a novelty hack. It&#8217;s a window into practical DNS manipulation, embedded networking, and the kind of resource-constrained problem-solving that translates directly to IoT deployments, edge computing, and infrastructure optimization. Let&#8217;s dig into how network-level ad blocking actually works, why the ESP32 makes sense for this task, and how you can implement similar DNS filtering techniques in your own environment.<\/p>\n<nav>\n<h2>Table of Contents<\/h2>\n<ul>\n<li><a href=\"#how-dns-adblocking-works\">How DNS-Based Ad Blocking Actually Works<\/a><\/li>\n<li><a href=\"#why-esp32\">Why the ESP32 Makes Sense for Network Services<\/a><\/li>\n<li><a href=\"#implementing-dns-filtering\">Implementing DNS Filtering: The Technical Deep Dive<\/a><\/li>\n<li><a href=\"#blocklist-management\">Managing and Updating Block Lists<\/a><\/li>\n<li><a href=\"#performance-considerations\">Performance and Memory Constraints<\/a><\/li>\n<\/ul>\n<\/nav>\n<h2 id=\"how-dns-adblocking-works\">How DNS-Based Ad Blocking Actually Works<\/h2>\n<p>Before you can appreciate what makes the ESP32 implementation clever, you need to understand the fundamental mechanism. When your browser requests <code>ads.example.com<\/code>, it first queries a DNS server to resolve that hostname into an IP address. Network-level ad blockers intercept this process, becoming the authoritative DNS server for your local network.<\/p>\n<p>The blocker maintains a list of known advertising and tracking domains. When a query matches one of these domains, instead of returning the legitimate IP address, it returns either 0.0.0.0 or 127.0.0.1\u2014addresses that go nowhere. The browser receives what looks like a valid DNS response, attempts to connect, fails immediately, and moves on. No bandwidth wasted downloading ads, no tracking pixels loaded, no third-party scripts executed.<\/p>\n<p>This approach has distinct advantages over browser-based blocking. It works for every device on your network\u2014smart TVs, mobile apps, IoT devices\u2014without requiring individual configuration. It operates at the network layer, meaning applications can&#8217;t detect or circumvent it the way they can browser extensions. For IT professionals managing home labs or small office networks, it&#8217;s infrastructure-level control.<\/p>\n<div style=\"background:#fef3c7;border-left:4px solid #f59e0b;padding:14px 18px;border-radius:6px;margin:20px 0;\"><strong>\ud83d\udca1 Pro Tip:<\/strong> DNS-based blocking fails against first-party tracking (ads served from the same domain as content) and encrypted DNS-over-HTTPS when devices bypass your local resolver. For comprehensive blocking, you need multiple layers of defense.<\/div>\n<h2 id=\"why-esp32\">Why the ESP32 Makes Sense for Network Services<\/h2>\n<p>The ESP32 family has become the go-to platform for embedded networking projects, and for good reason. The ESP32-C3 variant features a RISC-V processor, built-in WiFi, enough RAM to handle network buffers, and crucially\u2014extremely low power consumption. Unlike a Raspberry Pi pulling 2-5 watts, an ESP32 can run this workload on under 500mW.<\/p>\n<p>For IT professionals, this opens interesting deployment scenarios. Edge locations where power is constrained, always-on services where electricity costs matter, or redundant DNS filtering that doesn&#8217;t require full compute resources. The ESP32 can run for days on a small battery backup, ensuring your network filtering survives brief power outages without requiring a full UPS.<\/p>\n<p>The hardware constraints also force elegant software design. With only 400KB of RAM and 4MB of flash storage, you can&#8217;t just import a bloated library or load millions of domain rules. This teaches the kind of optimization mindset that <a href=\"https:\/\/imp.i384100.net\/zxbRDr\" target=\"_blank\" rel=\"nofollow sponsored noopener\">Coursera<\/a> embedded systems courses emphasize\u2014every byte counts, every CPU cycle matters, and efficient data structures become mandatory rather than optional.<\/p>\n<h2 id=\"implementing-dns-filtering\">Implementing DNS Filtering: The Technical Deep Dive<\/h2>\n<p>Let&#8217;s look at the core DNS server implementation. While the ESP32-C3 Adblock project uses Arduino framework code, the concepts translate to any embedded platform. Here&#8217;s a simplified DNS response handler that demonstrates the filtering logic:<\/p>\n<pre><code>\/\/ DNS packet handler for ESP32\nvoid handleDNSRequest(WiFiUDP &udp) {\n  char packetBuffer[512];\n  int packetSize = udp.parsePacket();\n  \n  if (packetSize) {\n    udp.read(packetBuffer, 512);\n    \n    \/\/ Extract queried domain from DNS packet\n    String domain = extractDomain(packetBuffer);\n    \n    \/\/ Check against blocklist (stored in flash memory)\n    if (isBlocked(domain)) {\n      \/\/ Return null route response (0.0.0.0)\n      sendBlockedResponse(udp, packetBuffer);\n    } else {\n      \/\/ Forward to upstream DNS (e.g., 1.1.1.1)\n      forwardToUpstream(udp, packetBuffer, packetSize);\n    }\n  }\n}\n<\/code><\/pre>\n<p>The critical performance bottleneck is the <code>isBlocked()<\/code> function. With blocklists containing hundreds of thousands of domains, a naive linear search would make DNS resolution painfully slow. This is where data structure choice becomes crucial\u2014hash tables, bloom filters, or radix trees all offer different tradeoffs between memory usage, lookup speed, and false positive rates.<\/p>\n<p>For those coming from web development or data science backgrounds, working with these constraints feels different. Unlike the environment you&#8217;d encounter in <a href=\"https:\/\/datacamp.pxf.io\/YR9dQK\" target=\"_blank\" rel=\"nofollow sponsored noopener\">DataCamp<\/a> courses focused on high-level data manipulation, embedded networking forces you to think about memory alignment, pointer arithmetic, and hardware-specific optimizations. It&#8217;s closer to systems programming than application development.<\/p>\n<h3>Handling DNS Protocol Details<\/h3>\n<p>DNS isn&#8217;t just simple request-response. The protocol includes query IDs for matching responses to requests, support for multiple question and answer sections, compression using pointer offsets, and various record types (A, AAAA, CNAME, MX, etc.). Your embedded DNS server needs to handle at minimum A and AAAA records for IPv4 and IPv6 addresses.<\/p>\n<pre><code>\/\/ Construct DNS response packet for blocked domain\nvoid sendBlockedResponse(WiFiUDP &udp, char* request) {\n  char response[512];\n  \n  \/\/ Copy query ID and flags from request\n  memcpy(response, request, 2);  \/\/ Transaction ID\n  \n  \/\/ Set response flags: standard query response, no error\n  response[2] = 0x81;  \/\/ QR=1 (response), Opcode=0, AA=1\n  response[3] = 0x80;  \/\/ RA=1 (recursion available)\n  \n  \/\/ Questions=1, Answers=1, Authority=0, Additional=0\n  response[4] = request[4]; response[5] = request[5];  \/\/ QDCOUNT\n  response[6] = 0x00; response[7] = 0x01;  \/\/ ANCOUNT\n  response[8] = 0x00; response[9] = 0x00;  \/\/ NSCOUNT\n  response[10] = 0x00; response[11] = 0x00;  \/\/ ARCOUNT\n  \n  \/\/ Copy question section, add answer pointing to 0.0.0.0\n  int qlen = copyQuestion(response + 12, request + 12);\n  addNullAnswer(response + 12 + qlen);\n  \n  udp.write(response, 12 + qlen + 16);\n}\n<\/code><\/pre>\n<p>Understanding these packet-level details matters for troubleshooting. When DNS resolution mysteriously fails, being able to capture packets with tcpdump and decode the flags, counts, and section layouts separates senior engineers from junior ones who only know how to restart services and hope.<\/p>\n<h2 id=\"blocklist-management\">Managing and Updating Block Lists<\/h2>\n<p>Static blocklists become stale quickly. New advertising networks emerge, tracking domains rotate, and previously blocked legitimate services need whitelisting. The ESP32&#8217;s limited storage means you can&#8217;t just download the full EasyList with millions of entries.<\/p>\n<p>Practical approaches include curated compact lists (10,000-50,000 domains covering the most common offenders), aggressive domain wildcarding (blocking *.doubleclick.net instead of individual subdomains), and periodic updates fetched over WiFi. The update process itself requires careful design\u2014you can&#8217;t afford to brick the device with a corrupted download.<\/p>\n<div style=\"background:#fef3c7;border-left:4px solid #f59e0b;padding:14px 18px;border-radius:6px;margin:20px 0;\"><strong>\u26a0\ufe0f Common Mistake:<\/strong> Storing blocklists in RAM seems fast but wastes precious memory. Use ESP32 flash storage with memory-mapped reads\u2014slightly slower but allows much larger lists without exhausting RAM needed for network buffers.<\/div>\n<p>Versioning your blocklist and implementing rollback capability prevents self-inflicted outages. A configuration option to temporarily disable filtering (returning to straight DNS forwarding) gives you an escape hatch when troubleshooting whether the blocker is causing connectivity issues.<\/p>\n<h2 id=\"performance-considerations\">Performance and Memory Constraints<\/h2>\n<p>Real-world DNS performance requirements are demanding. Users expect sub-10ms response times for cached results and sub-100ms for upstream forwarding. The ESP32&#8217;s 160MHz CPU is plenty fast for packet processing, but memory becomes the limiting factor. Each open UDP socket, DNS query in flight, and network buffer consumes precious RAM.<\/p>\n<p>Profiling becomes essential. The Arduino framework includes tools for tracking heap usage, stack depth, and identifying memory leaks. For production deployments, implement monitoring that tracks query rates, cache hit ratios, upstream timeouts, and memory watermarks. Log anomalies to syslog or a lightweight time-series database.<\/p>\n<p>Consider DNS caching carefully. It multiplies effectiveness by avoiding repeated upstream queries, but each cache entry consumes memory. A simple LRU (Least Recently Used) cache with 100-500 entries provides significant benefit without exhausting resources. TTL (Time To Live) values from upstream responses determine how long entries remain valid.<\/p>\n<p>The beauty of this project is that it combines network administration, embedded programming, protocol understanding, and resource optimization\u2014skills that span IT disciplines. Whether you&#8217;re managing corporate infrastructure, building IoT products, or just want cleaner home network traffic, the principles translate directly.<\/p>\n<div style=\"background:#f8f8f8;color:#555;padding:14px 18px;border-radius:8px;margin-top:32px;font-size:14px;line-height:1.6;\"><span style=\"color:#222;font-weight:600;\">Stay in the loop<\/span> \u2014 join 125,000+ IT professionals following Networkyy: <a href=\"https:\/\/www.instagram.com\/networkyy\" target=\"_blank\" style=\"color:#7c3aed;font-weight:600;text-decoration:none;\" rel=\"noopener\">Instagram<\/a> \u00b7 <a href=\"https:\/\/www.facebook.com\/ITnetworkyy\/\" target=\"_blank\" style=\"color:#7c3aed;font-weight:600;text-decoration:none;\" rel=\"noopener\">Facebook<\/a> \u00b7 <a href=\"https:\/\/www.threads.com\/@networkyy\" target=\"_blank\" style=\"color:#7c3aed;font-weight:600;text-decoration:none;\" rel=\"noopener\">Threads<\/a> \u00b7 <a href=\"https:\/\/medium.com\/@mattouchi6\" target=\"_blank\" style=\"color:#7c3aed;font-weight:600;text-decoration:none;\" rel=\"noopener\">Medium<\/a><\/div>\n<div style=\"background:linear-gradient(135deg,#1e1b4b,#6d28d9 55%,#db2777);border-radius:16px;padding:30px 24px;text-align:center;box-shadow:0 10px 30px rgba(109,40,217,0.35);\">\n<div style=\"display:inline-block;background:#facc15;color:#1e1b4b;font-size:11px;font-weight:800;letter-spacing:0.5px;padding:5px 12px;border-radius:999px;margin-bottom:14px;\">\ud83d\udd25 RECOMMENDED FOR YOU<\/div>\n<h3 style=\"margin:0 0 10px;font-size:20px;color:#fff;font-weight:800;line-height:1.3;\">Master Embedded Systems and IoT<\/h3>\n<p style=\"margin:0 0 20px;color:#e9d5ff;font-size:13.5px;line-height:1.6;\">Build production-ready embedded networking projects from DNS servers to edge computing devices. Learn the hardware-software integration skills that command premium salaries in IoT and infrastructure roles.<\/p>\n<p><a href=\"https:\/\/imp.i384100.net\/zxbRDr\" target=\"_blank\" rel=\"nofollow sponsored noopener\" style=\"display:inline-block;background:#a3e635;color:#1e1b4b;font-weight:800;padding:13px 30px;border-radius:10px;font-size:14.5px;box-shadow:0 4px 14px rgba(163,230,53,0.5);text-decoration:none;\">Start Learning on Coursera \u2192<\/a><\/div>","protected":false},"excerpt":{"rendered":"<p>Learn to deploy DNS-based ad blocking on ESP32 hardware. Real-world network filtering techniques for IT pros using embedded systems.<\/p>","protected":false},"author":2,"featured_media":926,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":"","_yoast_wpseo_title":"Building Network-Level Ad Blocking with ESP32 Microcontrollers - Networkyy","_yoast_wpseo_metadesc":"Learn to deploy DNS-based ad blocking on ESP32 hardware. Real-world network filtering techniques for IT pros using embedded systems.","_yoast_wpseo_focuskw":"ESP32 ad blocking","rank_math_title":"","rank_math_description":"","rank_math_focus_keyword":""},"categories":[1],"tags":[],"class_list":["post-927","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-uncategorized"],"contentshake_article_id":"","brizy_media":[],"_links":{"self":[{"href":"https:\/\/networkyy.com\/fr\/wp-json\/wp\/v2\/posts\/927","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/networkyy.com\/fr\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/networkyy.com\/fr\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/networkyy.com\/fr\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/networkyy.com\/fr\/wp-json\/wp\/v2\/comments?post=927"}],"version-history":[{"count":0,"href":"https:\/\/networkyy.com\/fr\/wp-json\/wp\/v2\/posts\/927\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/networkyy.com\/fr\/wp-json\/wp\/v2\/media\/926"}],"wp:attachment":[{"href":"https:\/\/networkyy.com\/fr\/wp-json\/wp\/v2\/media?parent=927"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/networkyy.com\/fr\/wp-json\/wp\/v2\/categories?post=927"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/networkyy.com\/fr\/wp-json\/wp\/v2\/tags?post=927"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}