Tunable Fabrics In article 2300428, Wei-Bing Lu, Quan Li, and co-workers present a wearable and tunable fabric microwave filter (TFMF) based on a spoof surface plasmon polariton (SSPP) structure and organic electrochemical transistors. The operating modes of the TFMF can be digitally controlled by applying different voltage sequences. The proposed TFMF exhibits excellent flexibility, high planar integration, and enhanced wearing comfort.