What are Media Settings in WordPress?

The Media Settings screen (Settings → Media in the WordPress dashboard) sets the maximum width and height in pixels for the medium and large image sizes WordPress generates from each upload, plus the exact width and height for thumbnails. Two more options live on the same screen: thumbnail cropping and month- and year-based upload folders.

The default image sizes

Each time you upload an image to the Media Library, WordPress automatically generates several copies of it at different sizes. For each sufficiently large image, you’ll get a thumbnail (150×150 pixels, cropped to exactly that size by default), a medium size (a maximum of 300×300), and a large size (a maximum of 1024×1024). Those 3 are the sizes you can adjust on this screen, and the uploaded original is kept untouched as the full size. You can choose any of them when placing an image on your site.

Sizes this screen doesn’t control

Those defaults aren’t the whole set. WordPress also creates a 768-pixel-wide medium_large size (added in WordPress 4.4) and 1536- and 2048-pixel copies for high-density screens (added in 5.3), none of which appear on this screen. Uploads wider or taller than 2,560 pixels get an extra scaled-down copy that WordPress serves in place of the original. Themes and plugins can register their own sizes with add_image_size(), too. The Twenty Fourteen theme, for example, adds a 1038×576 size. WordPress never upscales, so a small image gets fewer copies, but a large photo can easily produce 7 files or more. In short, your uploads folder holds more copies per image than this screen suggests, and removing a theme’s extra sizes happens in code, not here.

Thumbnail cropping

You can turn cropping for thumbnails on or off; it’s on by default. Cropped thumbnails come out at exactly the width and height you set, with the edges trimmed to fit. Uncropped thumbnails scale proportionally, like the medium and large sizes. Neither option stretches the image, so choose cropping when you want a uniform grid of squares and proportional scaling when the whole picture matters.

Month- and year-based upload folders

The screen’s last option, checked by default, organizes uploads into folders by year and month. You won’t see these folders in the Media Library; they sit in the wp-content/uploads folder on the server. With the box checked, a file uploaded in June 2018 lands in wp-content/uploads/2018/06, and WordPress creates those folders automatically at upload time as long as wp-content is writable. The structure matters when you browse files over SFTP or a file manager: years of uploads stay navigable instead of piling up in a single directory.

Changing the defaults

New dimensions apply only to images you upload after saving the change. Everything already in the Media Library keeps its existing copies until you regenerate them, either with a thumbnail-regeneration plugin or with WP-CLI’s wp media regenerate command. For a walkthrough of this and other image problems, see our guide to fixing 16 common image issues in WordPress.

As for whether to change anything: keep the defaults unless your theme’s layout needs different dimensions, such as a content column wider than 1,024 pixels that leaves the large size looking soft. Every size means another file created on each upload, so disk usage grows with every copy your site generates. When in doubt, leave the screen alone. You can always regenerate images later if you change your mind.