Set preview cache

Lightroom renders three types of previews: thumbnails, screen resolution images, and 1:1 previews. 1:1 previews have the same pixel dimensions as the original photos and display sharpening and noise reduction. All previews are stored in the folder where your catalog is located.

  1. Choose Edit > Catalog Settings (Windows) or Lightroom > Catalog Settings (Mac OS), and then click File Handling.
  2. Choose from the following menus:
    Standard Preview Size
    Specifies the maximum pixel dimension for the rendered preview. Choose the size that accommodates the display size you’re working with.

    Preview Quality
    Specifies the appearance of the previews. Low, Medium, and High are similar to the upper range of the quality scale for JPEG files.

    Automatically Discard 1:1 Previews
    Specifies when 1:1 previews are discarded based on the most recent access to the preview. 1:1 previews are rendered as needed and can make the library preview file large.