Abstract: Olaf is a portable, landmark-based, acoustic fingerprint-ing system released as open source software. Olaf runs on embedded platforms, traditional computers and in the browser. Olaf is able to extract fingerprints from an audio stream, and either store those fingerprints in a database, or find a match between extracted fingerprints and stored fingerprints. It implements an algorithm similar to the one described in a classic ISMIR paper and has similar retrieval performance. It facilitates the many use cases acoustic fingerprinting has to offer such as duplicate detection, meta-data coupling, and synchronization.