proxy files
You can use Final Cut Pro to transcode your original media to create proxy files, which are smaller files with a lower data rate. Proxy files increase editing performance and take up considerably less storage space than optimized files. This makes them a good choice for offline editing. Final Cut Pro creates video proxy files using either the Apple ProRes 422 Proxy or H.264 format. You can create proxy media in a variety of frame sizes from 12.5 percent to 100 percent of the original.