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PHP GD extension

GD is an extension for PHP that can open, resize, crop and save images. WordPress uses it to create the smaller copies of every image you upload: thumbnails, medium and large sizes, and the versions that themes need.

Why it matters

Section titled “Why it matters”

Those copies are what keeps pages fast. A theme can show a 400-pixel version instead of the 6,000-pixel original. Without an image editor, WordPress keeps only the original, and pages end up loading far larger files than they need. Cropping and rotating in the Media Library don’t work either.

WordPress can work with two image editors: Imagick, which it prefers when it’s available, and GD. One of the two is enough. Which image formats work depends on how GD was built: support for newer formats such as WebP and AVIF isn’t always included.

What influences it

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Server: Whether the extension is installed and enabled, and which image formats it was built with, is up to the hosting provider.

WordPress: WordPress chooses the editor for each task and uses GD when Imagick isn’t available or can’t handle the format. Plugins can change that choice.

In Permo

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Permo doesn’t show which image editor PHP has. It shows what matters most for speed: the Image formats card in System info, tab Server & System, says whether WordPress can create WebP and AVIF images on this server, with GD or Imagick; see image formats. WordPress’s own Site Health screen, under Tools, warns when PHP has neither GD nor Imagick.

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