When you preview a program, Premiere creates temporary files on your hard disk. These preview files contain the results of any effects that Premiere processed during a preview. If you preview the same work area more than once without making any changes, Premiere instantly plays back the preview files instead of processing the Timeline again. Similarly, preview files can save time when you export the final video program by using the processed effects already stored. Premiere stores the preview files in a folder you can specify.

To further save time, Premiere maintains existing preview files whenever possible. Preview files move along with their associated segment of the Timeline as you edit your project. When a segment of the Timeline is changed, Premiere automatically trims the corresponding preview file, saving the remaining unchanged segment.

The preview status for each clip in the Timeline window is indicated by a colored bar above the time ruler. When a preview file doesn't exist for a segment and needs to be generated, the indicator bar above that segment is red. When a preview file for the video segment exists, the indicator bar is green. When a preview for the audio segment exists, an additional bar attached below the indicator bar is light green. If all effects in a segment can be played in real time, there is no colored bar.

绿色的状态条表示该段可以预览（按ENTER键的播放是预览, 而不是SPACEBAR键的播放） 红色表示系统尚未生成预览临时文件 该区域内效果不能被预览。 当预览文件中含有音频时 在预览状态区的下面会有一个浅绿色的状态条