What are the field length limitations in DESelect?

salesforce marketing cloud imposes a 4000 character limit when defining field lengths in contact builder however, this restriction does not apply universally across sfmc in email studio, users can leave the field length empty, which defaults to varchar(max), allowing more than 4000 characters this difference can cause unexpected limitations for deselect segment users when working with data extensions created in contact builder how this affects deselect users if you create a data extension in contact builder, the 4000 character limit is enforced, meaning any field exceeding this limit may cause errors or truncation when used in deselect in contrast, if a data extension is created in email studio, leaving the length field empty allows varchar(max), enabling larger text storage however, this workaround is not officially supported across all sfmc studios and may lead to performance issues or unexpected behavior should you use the workaround? while email studio allows varchar(max), this is considered a legacy feature and may not be supported in the future if you choose this approach, be aware that there is no guarantee that sfmc will continue supporting it larger text fields may impact performance when querying or processing data if the data extension is later modified in contact builder, it may enforce the 4000 character limit, leading to data truncation recommended best practices to avoid potential issues, we recommend keep field lengths within 4000 characters whenever possible plan data structure carefully before creating a data extension to prevent unexpected limitations test queries and selections in deselect to ensure data is processed correctly consult sfmc support before relying on varchar(max) as a long term solution need help? if you're facing issues with field length limitations in sfmc while using deselect, reach out to your customer success manager or our support team for guidance