A lightweight, zero-dependency Ruby gem for resolving IPv4 and IPv6 addresses to geographic locations. Ships with an embedded MaxMind GeoLite2 database and a pure Ruby MMDB reader - no external gems, no API keys, no setup.

• Zero dependencies - pure Ruby MMDB reader, no native extensions, no external gems
• IPv4 and IPv6 - resolves to country, region, city, coordinates, timezone, and more
• Batteries included - GeoLite2 City database ships with the gem
• Fast - binary trie traversal over MaxMind's MMDB format
• Secure - no Marshal.load, rejects ambiguous IP octets with leading zeros
• Thread-safe - safe for Puma, Sidekiq, and other multi-threaded servers
• Fork-friendly - :file mode uses pread for shared OS page cache across workers
• Configurable - use the embedded database or point to your own .mmdb file

gem "ip_geo_lookup"

bundle install

That's it - the database is included.

require "ip_geo_lookup"

result = IpGeoLookup.lookup("8.8.8.8")
result = IpGeoLookup.lookup("2001:4860:4860::8888")

result = IpGeoLookup.lookup("8.8.8.8")

# Core fields
result.country_code  # => "US"
result.country_name  # => "United States"
result.region        # => "California"
result.city          # => "Mountain View"

# Extended fields
result.continent_code  # => "NA"
result.continent_name  # => "North America"
result.latitude        # => 37.386
result.longitude       # => -122.0838
result.time_zone       # => "America/Los_Angeles"
result.postal_code     # => "94035"

# Hash-style access
result[:country_code]  # => "US"

# Full MMDB record
result.raw  # => {"country" => {"iso_code" => "US", ...}, ...}

# Conversions
result.to_h  # => {country_code: "US", country_name: "United States", ...}
result.to_s  # => "Mountain View, California, United States (US)"

# Sorting
results = ips.map { |ip| IpGeoLookup.lookup(ip) }.compact.sort

Returns nil when the IP address is not found or is invalid:

IpGeoLookup.lookup("192.168.1.1")  # => nil  (private range)
IpGeoLookup.lookup("not_an_ip")    # => nil  (invalid format)
IpGeoLookup.lookup("08.8.8.8")     # => nil  (leading zeros rejected)
IpGeoLookup.lookup(nil)            # => nil

IpGeoLookup.configure do |config|
  config.database_path = "/path/to/GeoLite2-City.mmdb"
  config.mode = :memory  # optional: load entire DB into memory for single-process apps
end

IpGeoLookup.reload!   # re-reads from disk, respects configured path
IpGeoLookup.close     # releases file handle / memory
IpGeoLookup.metadata  # => {"database_type" => "GeoLite2-City", ...}

The gem includes a pure Ruby reader for MaxMind's MMDB binary format. On lookup:

1. The IP string is validated and converted to an integer in a single pass
2. The MMDB binary trie is walked (32 bits for IPv4, 128 for IPv6)
3. The matching record is decoded from the data section
4. A Result object is returned (or nil if no match)

Two I/O modes are available:

• :file (default) - keeps the file open and uses IO#pread for reads; the OS page cache shares data across forked workers automatically
• :memory - reads the entire file into a Ruby String for fastest lookups in single-process environments

• Ruby >= 2.6.0
• Zero external dependencies
• Thread-safe
• Linux, macOS, Windows

bundle install
bundle exec rake spec

Test fixtures are generated automatically during the test run - no external database file needed.

The embedded GeoLite2 City database lives in data/GeoLite2-City.mmdb (gitignored due to size). To update it:

1. Create a free account at MaxMind
2. Download the GeoLite2 City MMDB file
3. Copy it into the gem:

   cp /path/to/GeoLite2-City.mmdb data/GeoLite2-City.mmdb

4. Rebuild the gem: gem build ip_geo_lookup.gemspec

1. Fork it
2. Create your feature branch (git checkout -b feature/my-feature)
3. Commit your changes
4. Push to the branch
5. Create a Pull Request

Available as open source under the MIT License.

This product includes GeoLite2 data created by MaxMind, available from https://www.maxmind.com.