Aspiring guitarists currently face the obstacle of not being able to quickly check the accuracy of each note in the chords they are playing. Chord Checker is a Fourier-analysis based frequency analyzer that solves this problem by outputting the notes being played in a chord on the guitar. On the UI, users first upload recordings to the website and are then able to identify the individual notes that they have played and check if each one is picked up by the computer. The core python code is able to run input audio data from the user in .wav format, transform the audio signal to the frequency domain, and return both the magnitudes and phase shifts of the component frequencies. The program utilizes the curve-like properties of sound waves along with calculus and draws on findings in the field of signal processing. The site can be found at www.chordchecker.com. 