WordPress 7.1 changes where the work happens when someone uploads an image to your site. Instead of your server resizing, compressing, and converting that image, the uploader’s own browser does it before the file ever reaches you. WordPress.org detailed the change this week, and it is enabled by default in supporting browsers when WordPress 7.1 ships on August 19.

Why your server does this work today

When someone uploads an image in the block editor now, the file goes to your server first. PHP, using a library called GD or Imagick, generates the different thumbnail sizes WordPress needs, converts formats, fixes rotation, and shrinks oversized photos. That work costs server memory and CPU, and it is limited by whatever image library your host has installed. On shared hosting, a single large photo upload can time out or fail outright because the server runs out of memory mid-process.

What changes in WordPress 7.1

WordPress 7.1 moves that processing into the browser, using a technology called WebAssembly to run a high-quality image library (the same one, called libvips, that powers processing on many premium image services) directly on the visitor’s device. The browser generates the thumbnails and applies conversions and rotation fixes, then uploads the finished files to your server, which just stores them.

That shift brings a few concrete benefits:

  • Fewer failed uploads. Your server’s memory limits stop being the bottleneck, since the heavy lifting happens on the uploader’s device instead.
  • Smaller, better-compressed images. WordPress.org says JPEGs come out roughly 15% smaller with no visible quality loss, which means faster page loads for your visitors.
  • Modern formats just work. iPhone photos in HEIC format convert to JPEG automatically, and AVIF images upload correctly even if your server’s image library does not support AVIF.
  • Uploads survive network hiccups. Each thumbnail uploads on its own, so a dropped connection does not lose the whole batch. Failed pieces retry automatically.

The tradeoff is that more data travels over the network during upload, since the original image and every processed thumbnail all get sent to the server, rather than just the original. For most site owners that is a fair trade for a more reliable upload experience.

What you need to do

Nothing. This works automatically for anyone using a supporting browser, currently Chrome and Edge version 137 or later. If a visitor or editor is using Firefox or Safari, WordPress quietly falls back to the current server-side processing with no visible difference to them.

If you run a plugin that hooks into image uploads, for example to add a watermark or enforce a custom size, it is worth checking with your plugin developer that it still works correctly after you update to 7.1. The underlying WordPress hook plugins rely on fires the same way it always has, so most should need no changes.

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