Look up the autonomous system number and autonomous system organization
associated with IPv4 and IPv6 addresses.

 **Data Privacy**

To comply with data privacy regulations, please monitor our
[Do Not Sell My Personal Information Requests](https://www.maxmind.com/en/accounts/current/do-not-sell-requests)
page (login required) for IP addresses and networks that should not be used for
advertising or marketing purposes. You can automate retrieval of this list using
our [privacy exclusions API](/geoip/privacy-exclusions-api). 


## Binary Database

Binary databases make use of the
[MaxMind DB file format](https://maxmind.github.io/MaxMind-DB/). MaxMind
provides [official client APIs](/geoip/docs/databases/#official-client-apis)
that are open source. We also provide a list of
[unsupported and unofficial client APIs](/geoip/docs/databases/#unofficial-client-apis)
and
[unsupported and unofficial integrations](/geoip/docs/databases/#integrations)
with various applications.

You can also use the [mmdbinspect tool](https://github.com/maxmind/mmdbinspect)
(in beta), a command line interface built with Go, to look up one or more IPs
from one or more MMDB databases and receive output in a parsable JSON format.


[Learn about the fields in the binary version of this database on our binary
database field reference page.](binary/)

## CSV Database

In addition to our MaxMind DB binary format, we also offer GeoIP and GeoLite
databases in a CSV format suitable for importing into a SQL database. The CSV
files are shipped as a single
[zip file](<https://en.wikipedia.org/wiki/Zip_(file_format)>).




The zip file itself is named `GeoLite2-ASN-CSV_{YYYYMMDD}.zip`.
The downloaded zip file contains a single directory which in turn
contains several files. That directory is named
`GeoLite2-ASN-CSV_{YYYYMMDD}`.


The files in this zip archive are:

| Filename | Description |
|----------|-------------|
| `LICENSE.txt` | End user license |
| `COPYRIGHT.txt` | Copyright statement |
| `GeoLite2-ASN-Blocks-IPv4.csv` | CSV file containing data on IPv4 addresses |
| `GeoLite2-ASN-Blocks-IPv6.csv` | CSV file containing data on IPv6 addresses |


All the CSV files start with a single header row containing column names. The
specific column names and their contents are detailed below. The files are
encoded as UTF-8.


### Blocks Files

There are two CSV files for network blocks, one each for IPv4 and IPv6 blocks.
These are named `GeoLite2-ASN-Blocks-IPv4.csv` and
`GeoLite2-ASN-Blocks-IPv6.csv` respectively.



<div class="table">
  <table>
    <tbody>
      <tr>
        <th>Data field name</th>
        <th>Type</th>
        <th>Data field description</th>
      </tr>

      <tr>
        <td>network</td>
        <td>IP network as a string</td>
        <td>
          This is the IPv4 or IPv6 network in CIDR format such as “2.21.92.0/29”
          or “2001:4b0::/64”. We offer a utility to convert this column to
          start/end IPs or start/end integers. See
          <a href="#conversion-utility">the conversion utility section</a> for
          details.
        </td>
      </tr>

      <tr>
        <td>autonomous_system_number</td>
        <td>integer</td>
        <td>
          <p>
            The
            <a href="https://en.wikipedia.org/wiki/Autonomous_system_(Internet)"
              >autonomous system</a
            >
            number associated with the IP address.
          </p>
          <p>
            <a
              href="https://support.maxmind.com/knowledge-base/articles/maxmind-ip-network-data#autonomous-system-data"
              >Learn more about autonomous system data on our Knowledge Base.</a
            >
          </p>
        </td>
      </tr>

      <tr>
        <td>autonomous_system_organization</td>
        <td>string</td>
        <td>
          <p>
            The organization associated with the registered autonomous system
            number for the IP address.
          </p>
          <p>
            <a
              href="https://support.maxmind.com/knowledge-base/articles/maxmind-ip-network-data#autonomous-system-data"
              >Learn more about autonomous system data on our Knowledge Base.</a
            >
          </p>
        </td>
      </tr>
    </tbody>
  </table>
</div>


### Conversion Utility

We've created a
[small utility program](https://github.com/maxmind/geoip2-csv-converter) to
allow you to convert a GeoIP CSV file's representation of IP addresses to
another format. You can choose between start/end IP addresses, with the
addresses represented as strings or integers.

The program is available from our
[geoip2-csv-converter GitHub project releases tab.](https://github.com/maxmind/geoip2-csv-converter/releases)


## Example Files

We maintain example files in CSV and MMDB format. The files contain dummy data
rather than real GeoIP data.


### CSV Example Files

We maintain examples of the CSV files as they would be downloaded from the account portal:



- [GeoLite2-ASN-CSV_Example.zip](/examples/GeoLite2-ASN-CSV_Example.zip)
  

### MMDB Example Files

We maintain test MMDB files on GitHub:



- [GeoLite2-ASN-Test.mmdb](https://github.com/maxmind/MaxMind-DB/blob/main/test-data/GeoLite2-ASN-Test.mmdb)
  

Alternatively, you can [view all of our MMDB test data on GitHub](https://github.com/maxmind/MaxMind-DB/tree/main/test-data).

## Database Sizes

<!-- prettier-ignore-start -->

MaxMind databases can vary in size from release to release. If you are
working with file size limitations that are concerning, you should build
your integrations to fail gracefully in event of a significant size
change.

From May to August 2026, the database files varied in file size and number of networks as
follows:

| Database | CSV File Size | MMDB File Size | IPv4 Networks | IPv6 Networks |
|----------|---------------|----------------|---------------|---------------|
- databaseName: "GeoLite ASN"
  csvSizeRange: "55.7 MB - 58.8 MB"
  mmdbSizeRange: "12.0 MB - 12.4 MB"
  ipv4Range: "660,000 - 676,000"
  ipv6Range: "425,000 - 468,000"

The listed file sizes are for unpacked databases. Databases are
downloaded in a compressed format.


<!-- prettier-ignore-end -->

## Database Changes

We may add new data fields to the ASN database at any time.

New database fields are added as new columns to the right of existing columns in our CSV files,
and as additional data in our MMDB files.

Subscribe to our [GeoIP release notes](/geoip/release-notes) to be notified when new
data is added to our databases.

## APIs and Third-Party Integrations

You can find a complete list of official and unofficial client APIs, and
third-party integrations on the
[database documentation page](/geoip/docs/databases#client-apis).


## [GeoLite ASN binary database fields](/geoip/docs/databases/asn/binary/)
<p>The GeoLite ASN binary database contains the following fields for each network.</p>


<div class="table">
  <table>
    <tbody>
      <tr>
        <th>Data field name</th>
        <th>Type</th>
        <th>Data field description</th>
      </tr>

      <tr>
        <td>autonomous_system_number</td>
        <td>uint32</td>
        <td>
          <p>
            The
            <a href="https://en.wikipedia.org/wiki/Autonomous_system_(Internet)"
              >autonomous system</a
            >
            number associated with the IP address.
          </p>
          <p>
            <a
              href="https://support.maxmind.com/knowledge-base/articles/maxmind-ip-network-data#autonomous-system-data"
              >Learn more about autonomous system data on our Knowledge Base.</a
            >
          </p>
        </td>
      </tr>

      <tr>
        <td>autonomous_system_organization</td>
        <td>string</td>
        <td>
          <p>
            The organization associated with the registered autonomous system
            number for the IP address.
          </p>
          <p>
            <a
              href="https://support.maxmind.com/knowledge-base/articles/maxmind-ip-network-data#autonomous-system-data"
              >Learn more about autonomous system data on our Knowledge Base.</a
            >
          </p>
        </td>
      </tr>
    </tbody>
  </table>
</div>