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This documentation is curated by 2600Hz as part of the KAZOO open source project. Join our community forums here for peer support. Only features in the space are included as part of our 2600Hz Support Services plan.


The Kazoo number manager aims for the following:

  1. Provide a consistent interface to number management
  2. Abstract concepts of carriers, providers, converters, etc, to allow a more easily pluggable system
  3. Simplify how numbers move from various states and between accounts



The main entry point for number management is the knm_number module and its underlying #knm_number{} record. From here, numbers can be fetched, created, moved, assigned, and more.

A number document should look something like this:

   "_id": "+15556668743",
   "_rev": "6-8bed97b8a5bf5e89528a6d1b04bc0427",
   "pvt_db_name": "numbers%2F%2B1555",
   "pvt_state": "in_service",
   "pvt_ported_in": false,
   "pvt_module_name": "knm_bandwidth2",
   "pvt_modified": 63661152901,
   "pvt_created": 63658650265,
   "pvt_type": "number",
   "prepend": {
       "name": "My prepended name",
       "enabled": true
   "cnam": {
       "inbound_lookup": true,
       "display_name": "My display name"
   "pvt_assigned_to": "account0000000000000000000000002",
   "pvt_features": {
       "prepend": {
           "name": "My prepended name",
           "enabled": true
       "inbound_cnam": {
           "inbound_lookup": true
       "outbound_cnam": {
           "display_name": "My display name"

Numbers are stored in prefixed databases: +15556668743 is stored in numbers/+1555 with this id. When a number is assigned to an account, this document is copied from the numbers database into the account's database. When ownership changes to another account or when the number goes available, this account document is deleted.

Note: the number document in the numbers DB is the source of truth, above the one in account DBs.

Note: while a number document should exist in at most one account database, it is possible that a bug left some number documents in the wrong account databases. Use the Sync button from the owning account, to delete these number documents from the wrong account database.

Run sup kazoo_numbers_maintenance migrate {ACCOUNT_ID} or a full migration to make sure these documents are all in sync on {ACCOUNT_ID} or throughout your system. Do note though that this operation can take a long time, depending on the amount of accounts and numbers in your system.


The knm_number API functions often take a second argument of options. These are encapsulated in the knm_options module, including a handy -type for better type checking.

Bulk operations#

When you want to perform operations on a list of numbers, knm_ops provides a nice way to do that, versus iterating over the list yourself.

Phone Numbers#

The knm_phone_number module (and #knm_phone_number{} record) represent the number document stored in the database and control logic for changing fields of the number document, as well as accessors for various fields. The module/record are not meant to be used outside of the KNM library; instead it is wrapped in the #knm_number{} record and accessed via other modules.


The knm_carriers module provides the interface to the enabled carrier modules, allowing upper-level applications a single interface to interact with carriers. The primary API concerns searching for, acquiring, and disconnecting numbers from the underlying carrier modules, as well as standardizing the results (including errors) across all carrier modules.

The knm_gen_carrier module is the Erlang behaviour which all carrier modules must implement.


The knm_providers module provides the interface to feature provider modules. Just as the knm_carriers module abstracts the carrier, knm_providers abstracts the provider modules, allowing providers to be added or removed without needing knowledge of which provider modules are in play.

The knm_gen_provider module is the Erlang behaviour which all provider modules must implement.

White-listing feature providers#

Number features (such as E911, CNAM, failover) can be whitelisted and blacklisted.

One can set the lists in this hierarchical order (if set, one takes precedence over the next, number document first):

  1. On the number document (undefined by default)
  2. On the number's reseller account document (undefined by default)
  3. In system_config/number_manager:
    • if system_config/number_manager/providers is set it will be used as the default list of allowed features
    • otherwise, the defaults of "features"."allow" are used
    • Note: local numbers are the only exception (see note below)

Each of these documents can both have a list of features allowed for use and forbidden from use:

  1. On number document: they are the root fields "pvt_features_allowed" and "pvt_features_denied"
  2. On reseller account document: the fields "features"."allow" and "features"."deny" under the number_manager category
  3. In system_config/number_manager: the fields "features"."allow" and "features"."deny"

By default, here is what the system_config/number_manager document looks like:

       "features": {
           "allow": [

To make sure your system has these defaults, run sup kazoo_numbers_maintenance reset_allowed_features_to_defaults_on_system_config.

On migration, sup kazoo_numbers_maintenance ensure_adminonly_features_are_reachable is run. This ensures that admins have access to admin-only features and also keeps the possible manual settings of system_config.

There are more maintenance commands to manage number features for the different documents listed above.

On local numbers#

Numbers that have knm_local (or knm_mdn) as a carrier are forbidden to have these external features:

  • CNAM i.e. features named "cnam", "inbound_cnam", "outbound_cnam"
  • E911 i.e. the feature named "e911"
  • port: the "port" feature only concerns numbers that were ported into the system

Note: if you want to set one or more of these features on numbers local to the system, you can either:

  • change their carrier from knm_local to knm_inventory using the "rename_carrier" feature (cleanest)
  • set the system_config/number_manager/local_feature_override boolean flag to true (fastest)
On admin-only features#

Some features can only be edited or used by admins of the system:

  • "carrier_name": allows an admin to change numbers' carrier module name

Change feature provider modules#

Features such as E911 and CNAM can be provisioned by different providers (Telnyx', Vitelity's, ...). These provider modules can be configured on the reseller document.

Here are their defaults and possible values:

  • "cnam_provider": "knm_cnam_notifier" (other possible values: "knm_telnyx_cnam", "knm_vitelity_cnam")
  • "e911_provider": "knm_dash_e911" (other possible values: "knm_telnyx_e911", "knm_vitelity_e911")

So in order for a reseller's sub-accounts to be able to use Telnyx's E911 feature, one must:

  1. Be allowed to edit the "e911" feature
  2. Set "e911_provider" to "knm_telnyx_e911"

Then, these accounts' numbers which have an "e911" public field will be querying Telnyx' E911 services.


The knm_converters module abstracts how numbers are normalized, classified, and reconciled. The primary implementation is the regex-based system, but there are plans to integrate libphonenumber as another backend.


Activating features, numbers, calculating charges -- anything involving an account's service plan and phone numbers -- is processed through knm_services.


The knm_locality is a generic HTTP client for fetching locality data associated with a number. The module will POST to the configured URL appended with "/locality/metadata', sending a JSON payload of {"data":["DID1", "DID2"...]}.

The response is expected to be a JSON payload of {"status":"success","data":{...}} where "status"="success" indicates the query was successful (any other value is treated as an error) and "data" is a JSON object with the locality information of each supplied DID.


The knm_errors module takes various error returns from the knm modules and converts it to a normalized JSON error response for use by the higher-level code.


The knm_config module provides accessors for various system- and account-config values.