EPrints 3 Reference: Directory Structure - Metadata Fields - Repository Configuration - XML Config Files - XML Export Format - EPrints data structure - Core API - Data Objects
Metadata Fields: Base64 - Bigint - Boolean - Compound - Counter - Date - Email - Float - Id - Idci - Int - Itemref - Keywords - Longtext - Longtext_counter - Multilang - Name - Namedset - Pagerange - Recaptcha - Set - Subject - Text - Time - Timestamp - Url
Please refer to the notes in EPRINTS_PATH/archives/ARCHIVEID/cfg/cfg.d/recaptcha.pl.
If this files does not exist, copy EPRINTS_PATH/lib/defaultcfg/cfg.d/recaptcha.pl.example to the path above and edit it.
This field uses the Google "reCAPTCHA" service (https://www.google.com/recaptcha/intro/) and renders a Captcha (a test that humans can easily pass, but robots shouldn't be able to).
Note: This MetaField was updated in October 2017 to reCAPTCHA v2. The previous version of reCAPTCHA will cease to work in March 2018.
As for Id fields.
validate:recaptcha_mismatch - Phrase to display if reCAPTCHA submission errored in some way.