Limitations

User Identifiers

Each account must have a user identifier, either an email address or a username. Users may not have multiple email addresses. See this issue for more information.

User Searches

When using the Elasticsearch search engine, the maximum number of users returned for any search is 10,000 users. There is an open bug tracking this issue.

Field Lengths

FusionAuth stores most data in a database. Lengths of specific fields are documented in the database schema for your database type. Please download the database schema for your version of FusionAuth to review length limits for a particular column.

Many varchar columns have a length of 191. Why 191? In MySQL when using a utf8mb4 (4 byte character set) on an indexed column, MySQL limits the usable characters to 191 to account for the overhead of the 4 byte addressing. The InnoDB MySQL engine has a max index length of 767 bytes (for mysql 5.7.9, the earliest version of MySQL which Fusionauth supports). Because we are using utf8mb4 which allows up to 4 bytes per character, we end up with 767/4 ~ 191, so we set the column length to that.

API Keys

FusionAuth is API first and every entity can be managed by an API, with one exception: API keys cannot be created or managed via the API.

The only ways to create an API key are:

• Use the administrative user interface

• Kickstart which only works on fresh installations.

However, there is an open GitHub issue to create an API key management API.

Minimum Key Lengths

You can use FusionAuth to manage your cryptographic keys. Due to security considerations, FusionAuth won’t import keys below a certain length.

For RSA keys used to verify signatures, the minimum length is 1024. This key length is allowed as of FusionAuth 1.23.4 and supports external systems that rely upon this weak key length.

For RSA keys used for signing or any other purpose, the minimum length is 2048.

For ECC keys, the minimum length is 256.

See the Keys API for more, including supported algorithms and lengths.

Default Entities

There are a number of default entities which cannot be removed. Additionally, there are limits to modifying these entities.

This includes:

• The Default tenant

• The FusionAuth application, which resides in the Default tenant

• The Default theme, which is read only

• The FusionAuth application roles, which may be assigned to users, but are immutable

SAML

FusionAuth supports SAML both as an Identity Provider (IdP) and as a Service Provider (SP).

The IdP implementation has certain limitations. Version 2.0 is supported; other SAML versions are unsupported.

FusionAuth supports two NameIDPolicy values:

• urn:oasis:names:tc:SAML:1.1:nameid-format:emailAddress

• urn:oasis:names:tc:SAML:1.1:nameid-format:unspecified

Please examine the NameIDPolicy of the software package for which you are configuring FusionAuth as the IdP to determine if these NameIDPolicy values are supported.

There is an open feature request to support urn:oasis:names:tc:SAML:2.0:nameid-format:persistent but this NameIDPolicy is currently unsupported.

FusionAuth supports the following SAMLv2 bindings:

• HTTP Redirect

• HTTP POST

Other bindings are not supported.

Identifiers

Identifiers (Ids) for entities in FusionAuth are UUIDs.

If you are creating an entity, such as an application, with the FusionAuth API, you can specify this Id, as long as it is a valid UUID. This works for users, applications, and tenants, among others, and makes it possible to avoid breaking external systems dependent on existing identifiers.

Data Type Changes In 'data' fields

FusionAuth provides data fields on many types of objects:

• Applications

• Tenants

• Groups

• Users

• Registrations

• Consent

If you are using the Elasticsearch search engine, the user.data and registration.data fields are indexed by Elasticsearch.

For example, you could create a field called user.data.migrated and store a boolean value in it. If you later set that field to an object value for any user, you won’t be able to find that user. Other users added after this user will be found, however, as long as they have the correct boolean value for the user.data.migrated field (or no value).

Elasticsearch requires fields to have the same data type across all indexed objects. In the example above, once Elasticsearch "knows" that user.data.migrated is a boolean, it expects this field, if present, to be a boolean for all users.

Therefore, you should not change the data type of fields stored in the user.data and registration.data fields across users.

Other object data fields may in the future be indexed by Elasticsearch. Therefore, it is recommended to have a consistent schema for all data fields.

This limitation applies only to installations using the Elasticsearch search engine. However, if you start with the database search engine and eventually need to switch to the Elasticsearch search engine because the database search engine no longer meets your needs, if you have not enforced consistency in the data field types, you will not be able to do so.

What’s Not Limited

All other entities, including but not limited to the following, are limited only by the resources of your system:

• Users

• Applications

• Tenants

• Roles

• Groups

• Identity Providers such as SAML or OIDC connections

• API keys to allow for programmatic configuration of and interaction with FusionAuth

• Supported languages/locales

• Signing and verifying keys