Lacquer is an iOS app that detects fake lossless audio files by analyzing the actual audio content rather than file metadata, using FFT analysis to identify upscaled or re-encoded files. It offers on-device processing with no uploads or accounts required, displaying spectral evidence for its verdicts, and functions as a full lossless audio player supporting FLAC, ALAC, WAV, AIFF, MP3, AAC, and m4a formats.