Pi-hole
Pi-hole is an open-source, network-wide ad blocker that operates as a DNS sinkhole, filtering out advertisements, trackers, and other unwanted content from internet traffic across all connected devices without requiring any client-side software installation.[1] Developed as a lightweight solution typically deployed on low-power Linux-based hardware such as a Raspberry Pi, it acts as the primary DNS server for the local network, redirecting requests to known ad-serving domains to a "black hole" to prevent their loading.[2] By leveraging blocklists of malicious or intrusive domains, Pi-hole enhances privacy, reduces bandwidth usage, and improves overall network performance, making it particularly effective for blocking ads in non-traditional environments like mobile apps and smart TVs.[1] Key features of Pi-hole include a responsive web-based dashboard for monitoring DNS queries, viewing real-time statistics, and managing blocklists, as well as built-in support for long-term data logging and customizable privacy settings.[2] It can function as an integrated DHCP server to automatically configure devices to use its DNS services and supports advanced integrations such as VPN setups for remote ad blocking.[2] The software is community-driven, maintained by a global team of developers, and available for installation via an automated script on supported operating systems or through Docker containers for easier deployment.[3] Recent versions, such as Pi-hole v6 released in early 2025, introduce enhancements like an embedded web server, redesigned user interface, and improved HTTPS support to bolster security and usability.[4]History and Development
Origins and Founding
Pi-hole was founded in the summer of 2014 by Jacob Salmela, a Linux administrator from Minnesota, who developed it as a personal script to block advertisements across an entire home network using a Raspberry Pi.[5] Salmela's initial motivations stemmed from frustration with the limitations of browser-based ad-blocking extensions, which required installation on each device and failed to cover non-browser traffic, prompting him to seek a centralized, network-wide solution that operated transparently without per-device configuration.[5] Inspired by the shortcomings of commercial hardware like AdTrap, he aimed to create a more efficient alternative leveraging the low-cost Raspberry Pi hardware.[6] The project quickly gained early adoption through community platforms, with Salmela sharing his script on Reddit and GitHub, where it attracted interest from users seeking similar ad-blocking capabilities.[6] This grassroots sharing led to community forks and contributions, culminating in the establishment of an official GitHub repository later in 2014, which formalized the project's development and hosted its open-source code.[5] The influx of user feedback and enhancements during this informal phase laid the groundwork for broader accessibility. To ensure long-term sustainability amid growing popularity and operational needs, Pi-hole transitioned to a structured entity with the formation of Pi-hole, LLC in 2018, supported by community donations and merchandise sales while maintaining its open-source ethos. This shift allowed the project to fund development and legal operations without compromising its commitment to free, network-level ad blocking. Over time, it evolved from a simple script into a full-featured software solution.Key Milestones and Releases
Pi-hole's development has seen several significant version releases that introduced core functionalities enhancing its DNS sinkhole capabilities. The v3.0 release on May 1, 2017, marked a major advancement by incorporating the Faster Than Light (FTL) engine, which improved performance for DNS resolution and logging, addressing previous limitations in web interface speed.[7] This version also laid groundwork for automated blocklist management, with subsequent updates like v3.2 in December 2017 adding long-term statistics and an audit log for better monitoring.[8] Building on this, v4.0 arrived on August 6, 2018, introducing the FTLDNS engine—a customized fork of dnsmasq—for more efficient real-time statistics and API support, alongside regex blocking capabilities and initial Docker containerization for easier deployment.[9] These changes enabled finer control over domain blocking and expanded compatibility with containerized environments, reducing setup complexity for users. The v5.0 release on May 10, 2020, further refined blocklist handling with a new gravity database for automated updates, enhanced regex support for blacklisting, per-client blocking options, and integration with upstream DNS providers like Cloudflare for improved query forwarding.[10] Long-term statistics were bolstered for deeper analytics, allowing users to track blocking efficacy over extended periods without overwhelming resource use. In July 2025, Pi-hole experienced a data breach affecting approximately 30,000 donors, where names and email addresses were exposed due to a vulnerability in the GiveWP WordPress plugin used for donations. The project promptly disclosed the incident, mitigated the issue, and advised affected users to monitor for phishing.[11] Subsequent development emphasized containerization and security, with Docker support maturing through v5.x updates and v6.0's general release on February 18, 2025, which consolidated configuration management and added native HTTPS.[4] Regular security patches continued, culminating in v6.3 on October 25, 2025, which included IPv6 DHCP enhancements for better dual-stack network compatibility.[12]Technical Functionality
Core Mechanism as DNS Sinkhole
Pi-hole operates as a DNS sinkhole by functioning as a local DNS resolver on a network, intercepting Domain Name System (DNS) queries from connected devices before they reach external servers. When a device initiates a request to resolve a domain, such as for loading a webpage or app content, Pi-hole receives the query and examines it against a database of blocklists containing known ad, tracker, and malware domains. If the queried domain matches an entry in these blocklists, Pi-hole responds immediately with a null IP address, typically 0.0.0.0 for IPv4 or :: for IPv6, which directs the request to nowhere and effectively prevents the content from loading.[2][13] For non-blocked queries, Pi-hole forwards the request to configured upstream DNS servers, such as Google's 8.8.8.8 or Cloudflare's 1.1.1.1, to obtain the legitimate IP address and relay it back to the requesting device. This interception occurs network-wide once devices are configured to use Pi-hole's IP address as their DNS resolver, often via DHCP settings on the router, ensuring that all traffic— from computers and smartphones to IoT devices like smart TVs—passes through Pi-hole without requiring individual client-side installations. The result is comprehensive ad and tracker blocking at the network level, reducing bandwidth usage and enhancing privacy by stopping unwanted requests before they leave the local environment.[2][1] While effective, this mechanism can lead to overblocking, where legitimate domains are inadvertently included in blocklists and blocked, necessitating manual whitelisting to restore access. In its basic setup, Pi-hole does not natively support serving encrypted DNS protocols like DNS over HTTPS (DoH) or DNS over TLS (DoT), though upstream connections to secure resolvers can be configured using additional tools such as cloudflared.[14][15]Domain Blocking and List Management
Pi-hole's domain blocking relies on the gravity script, which fetches and consolidates blocklists into a unified database for efficient DNS resolution. The script retrieves lists from URLs in the adlists table of the SQLite-based gravity.db, downloads the content using supported protocols like HTTP and HTTPS, parses domains while filtering invalid entries and comments, merges them, eliminates duplicates via indexing, and stores unique domains in the gravity table for subsequent blocking by the DNS engine.[16][17][18] Users source blocklists from established providers to enhance coverage, including StevenBlack's unified hosts files for broad ad and malware blocking, Firebog's categorized collections for targeted filtering of ads, trackers, and threats, and OISD's aggregated list for comprehensive privacy protection; these enable combining over 100 lists, with overlaps managed during gravity processing to optimize the final set.[19] Blocklist updates occur automatically weekly through a cron job in /etc/cron.d/pihole, executing the gravity script at a randomized time between 3:00 and 5:00 AM local time on Sundays to minimize load; manual updates are available via the web interface's "Update" button or the CLI commandpihole -g, which rebuilds the database and reports changes like new or unchanged domains.[16][20]
Customization allows precise control, with users adding or removing domains to local lists using CLI tools such as pihole allow [domain.com](/page/Domain.com) for whitelisting or pihole deny [domain.com](/page/Domain.com) for explicit blacklisting, directly inserting entries into the antigravity and gravity tables; regex support further enables pattern-based blocking, for example, ((^)|(\.))doubleclick\.net to intercept all subdomains and variants of ad-serving hosts, applied via the domainlist table (type 3) and reloaded with pihole restartdns.[14][21]
The system tracks blocklist statistics in the adlists table, recording domains per list, invalid counts, and update status; after merging, typical configurations yield 500,000 to 1 million unique blocked domains, as duplicates from combined lists reduce the effective total from raw entries often exceeding 1-2 million.[17][22][23]
False positives are mitigated through whitelist integration, where added domains in the antigravity table override gravity blocks with higher priority; audit tools, including database queries and log reviews, assist in identifying and correcting overblocks by examining matched domains and their sources.[14][17]
Features and Capabilities
User Interface and Monitoring
The Pi-hole web administration interface serves as the primary tool for users to monitor and manage DNS blocking activity, accessible via the local network address http://pi.hole/admin or the device's IP address followed by /admin, with native HTTPS support available since version 6.0. In Pi-hole v6 (released February 2025), the interface features an embedded web server integrated into the pihole-FTL engine, replacing previous dependencies on lighttpd and PHP, with new pages implemented in Lua for improved performance. The redesigned user interface, built on elements of the AdminLTE framework, includes Basic and Expert modes for customized views and offers a responsive design that adapts to various screen sizes, ensuring usability on desktops, tablets, and mobile devices.[4][24] The dashboard provides an overview of key metrics, including total DNS queries processed, percentage of domains blocked, top blocked domains, and graphs depicting client activity over time, such as pie charts for query types (e.g., A, AAAA) and line graphs for hourly or daily trends. These visualizations, powered by the Pi-hole FTL (Faster Than Light) engine, enable real-time monitoring of network traffic and blocking efficacy without requiring external tools, with server-side pagination added in v6 for efficient handling of large query logs.[24][25][4] The FTL engine, integrated directly into Pi-hole, handles real-time DNS query logging and maintains a long-term SQLite3 database for historical data retention, defaulting to 365 days of query records to track trends like weekly or monthly blocking patterns.[26][25] It also exposes API endpoints that allow the web interface and external applications to retrieve statistics, such as query counts and client-specific data, directly from memory for efficient, low-latency access.[25] Central to monitoring is the query log, a searchable interface displaying all incoming DNS requests with details on domains, timestamps, client IP addresses, and resolution status (blocked, forwarded, or cached). Users can apply filters to view only blocked queries, permitted ones, or activity from specific clients, facilitating troubleshooting and analysis of network behavior.[26] For security and customization, the interface supports password protection configurable through its settings, restricting access to authorized users. It includes light and dark theme options, such as deep-midnight and high-contrast variants, selectable via the web interface settings, to improve visibility in different lighting conditions. Additionally, users can export logs in formats suitable for analysis and opt-in to share anonymized telemetry data with the Pi-hole team to contribute to project improvements, with all sharing explicitly disabled by default.[28]Integration and Customization Options
Pi-hole supports router-level integration by configuring it as the primary DNS server through the router's DHCP settings, enabling automatic adoption across all connected devices without manual configuration on individual clients. This setup ensures that DNS queries from the entire network are routed through Pi-hole for ad and tracker blocking, leveraging its built-in DHCP server if the router lacks custom DNS options. To implement this, users disable the router's DHCP and enable Pi-hole's, specifying the network range and gateway, which delegates IP assignment and DNS resolution network-wide.[29] For remote access and enhanced privacy, Pi-hole integrates with VPN solutions such as WireGuard and OpenVPN, allowing users to route traffic through the Pi-hole instance from external networks for consistent blocking. WireGuard, recommended over the no longer recommended OpenVPN for its superior performance and simplicity, can be set up alongside Pi-hole to tunnel DNS queries securely, often on cloud instances or home servers. Additionally, Pi-hole pairs with Unbound, an open-source recursive DNS resolver, to handle upstream queries independently, reducing reliance on third-party resolvers and improving privacy by validating DNSSEC records directly.[30][31][32] The Pi-hole API, an enhanced RESTful interface using JSON and standard HTTP methods since v6, enables programmatic control for custom scripts and integrations, such as automating blocklist updates or querying statistics. Developers can use endpoints for tasks like enabling/disabling blocking or retrieving query logs, with authentication via API keys to secure access. In home automation, it integrates with platforms like Home Assistant through official plugins, allowing actions such as toggling ad-blocking via automations or monitoring Pi-hole stats in dashboards, though compatibility requires API version alignment. Telemetry data from the API can also feed into scripts that refine blocklists by analyzing query patterns.[33][34][35][4] Conditional forwarding enhances local network resolution by directing reverse DNS queries for specific domains, such as .local for printers or IoT devices, to the router or DHCP server, preventing resolution failures while maintaining Pi-hole's blocking for external domains. Configured via the pihole.toml file under the [dns] section with revServers as of v6's consolidated configuration, it specifies CIDR ranges and target servers, ensuring hostnames appear in Pi-hole's logs instead of IPs. Group management allows granular per-device policies by assigning clients to groups with tailored blocklists, allowlists, or regex filters, facilitating scenarios like whitelisting ads for smart TVs or stricter blocking for children's devices.[13][36][4] Beyond Raspberry Pi hardware, Pi-hole supports deployment in Docker containers for portability across Linux systems, using official images like pihole/pihole:latest (now based on Alpine Linux for a smaller footprint since v6) with docker-compose for easy setup, including volume mounts for configuration persistence and port mappings for DNS and web access. Virtual machine installations follow similar OS prerequisites, while cloud hosting on platforms like AWS EC2 or DigitalOcean Droplets extends accessibility, often combined with VPNs for remote management, though users must handle security groups and static IPs for reliability.[37][38][4]Installation and Usage
Hardware and Software Requirements
Pi-hole is designed to operate on lightweight hardware, with minimal requirements including at least 512 MB of RAM and 2 GB of free storage space, making it suitable for low-power devices such as the Raspberry Pi Zero W or any compatible Linux-based system.[39] For networks supporting a small number of devices, this setup suffices, provided the device includes Ethernet or Wi-Fi connectivity for network integration. Recommended configurations for better performance, particularly in households with 50 or more connected devices, involve more capable hardware like the Raspberry Pi 4 with 2 GB or greater RAM, which offers enhanced processing for higher query volumes without significant resource strain.[39] Pi-hole supports both ARM and x86 architectures, extending compatibility to a wide range of single-board computers and virtual machines. On the software side, Pi-hole requires a Linux-based operating system, with Raspberry Pi OS (formerly Raspbian) being the preferred choice for Raspberry Pi deployments due to its optimized integration. Officially supported distributions include Alpine, Armbian OS, Debian, CentOS Stream, Fedora, and Ubuntu, ensuring reliability on actively maintained versions that use systemd or sysvinit for service management.[39] Deployment via Docker is also fully supported on platforms like Ubuntu or Debian, allowing containerized operation with minimal host overhead through official images.[37] A static IP address is essential for stable DNS resolution, and the device must have ports 53 (TCP/UDP for DNS) and 80 (TCP for the web interface, or 443 for HTTPS) open and accessible within the local network, with firewall rules configured to permit traffic from client devices.[39] As an always-on network service, Pi-hole benefits from a device with reliable power supply and stable networking to maintain continuous ad-blocking and query handling. Mid-range hardware, such as a Raspberry Pi 3 or 4, can efficiently process over 100,000 DNS queries per day in typical home or small office environments, demonstrating its scalability for moderate loads. In 2025, the release of Pi-hole version 6 introduced an embedded web server that reduces dependency on external components like lighttpd and PHP, further lowering resource demands across supported platforms.[4]Setup Process and Configuration
The installation of Pi-hole on supported Debian-based operating systems, such as Ubuntu or Raspberry Pi OS, begins with a one-line automated script that downloads and executes the installer. Users execute the commandcurl -sSL https://install.pi-hole.net | [bash](/page/Bash) in the terminal after ensuring the system meets prerequisites like a static IP address and open ports for DNS (53 TCP/UDP).[40][3] This script prompts for selections during setup, including upstream DNS providers like Google's 8.8.8.8, and installs necessary components such as the dnsmasq-based blocking engine and web interface.[41]
Following installation, configure the host device with a static IP address to ensure reliable DNS service, typically via the operating system's network manager—for instance, editing /etc/dhcpcd.conf on Raspberry Pi OS to include static ip_address=192.168.1.x/24 and static domain_name_servers=127.0.0.1.[39] Next, verify and adjust upstream DNS settings in the web interface at http://pi.hole/admin under Settings > DNS, selecting providers like Quad9 or Cloudflare to forward unblocked queries. To secure the web interface, set a password using the command pihole -a -p, which prompts for a new password and applies it immediately.[29] As of Pi-hole v6 (released February 2025), configurations are consolidated into a single file at /etc/pihole/pihole.[toml](/page/toml), which the installer generates and the web interface manages.[4]
To integrate Pi-hole network-wide, update the router's DHCP settings to assign the Pi-hole device's IP address as the primary (and sole) DNS server for all clients, found under the router's LAN or DHCP configuration page. This ensures devices automatically use Pi-hole upon lease renewal; reboot clients or renew leases to apply changes. Test the configuration by running nslookup doubleclick.net (a commonly blocked ad domain) from a client device, which should return 0.0.0.0 if blocking is active, or ping the same domain to confirm no response.[42][43]
Initial configuration tweaks enhance functionality: execute pihole -g to update the gravity database, which pulls and merges blocklists into the local blacklist for immediate effect. Add custom blocklists via the web interface at Settings > Adlists by pasting URLs like https://raw.githubusercontent.com/StevenBlack/hosts/master/hosts and clicking Add, then run pihole -g to integrate them. For accurate log timestamps, set the system timezone with sudo timedatectl set-timezone America/New_York (replacing with the appropriate zone), ensuring query logs reflect local time.[16][44]
Basic troubleshooting addresses common issues: verify firewall rules allow inbound traffic on port 53 (TCP/UDP) using tools like ufw status on Ubuntu or [iptables](/page/Iptables) -L, adding rules if needed with [sudo](/page/Sudo) ufw allow 53. If the local hostname "pi.hole" fails to resolve, edit /etc/hosts on the host to include 192.168.1.x pi.hole (using the actual IP) and restart the network service.[39][45]