Error "custom-fields-too-long" in Auth0 Universal Login
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Overview
This article explains that the following error occurs when attempting to pass data from Universal Login pages to post-login Actions:
custom-fields-too-long
This error prevents successful authentication.
Applies To
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Auth0 Universal Login
Cause
The custom-fields-too-long error occurs because dynamically inserted ulp- prefixed content from Universal Login pages is subject to a 6000 bytes Binary JSON (BSON) limit. This limit applies to the total combined size of all such fields. When data exceeds this limit, the authentication endpoint rejects the request before Actions are executed. This validation represents a limit on the size of the incoming form submission payload, not a rate limit.
Solution
To resolve the custom-fields-too-long error, adhere to the 6000 bytes BSON limit for dynamically inserted ulp- fields.
