Recital 26:

To determine whether a natural person is identifiable, account should be taken of all the means reasonably likely to be used, such as singling out, either by the controller or by another person to identify the natural person directly or indirectly. To ascertain whether means are reasonably likely to be used to identify the natural person, account should be taken of all objective factors, such as the costs of and the amount of time required for identification, taking into consideration the available technology at the time of the processing and technological developments.

Since the concepts mentioned in the comment, IP and browser information, are already being used to single people out for tracking, those particular types of information can definitely be viewed as the equivalent concept under GDPR, as defined in Recital 26.