Existence of data processing

According to the definition in Article 4 GDPR – Definitions,  "personal data" means any information relating to an identified or identifiable natural person. The usernames, although some of them are emails and some of them are not, they do lead to the identification of natural persons. They are considered pseudonymized personal data. According to the definition in the same Article 4 GDPR, "pseudonymization" means the processing of personal data in such a manner that the personal data can no longer be attributed to a specific data subject without the use of additional information, provided that such additional information is kept separately and is subject to technical and organizational measures to ensure that the personal data are not attributed to an identified or identifiable natural person.

So storing this list of usernames is considered processing of personal data, also according to the definition in Article 4 GDPR, where ‘processing’ means any operation or set of operations which is performed on personal data or on sets of personal data.

Please also consult these links:

• Article 4 GDPR – Definitions: https://advisera.com/gdpr/definitions/
• A summary of 10 key GDPR requirements: https://advisera.com/eugdpracademy/knowledgebase/a-summary-of-10-key-gdpr-requirements/
• Understanding 6 key GDPR principles: https://advisera.com/eugdpracademy/knowledgebase/understanding-6-key-gdpr-principles/