Getting started

Image Resizer does one thing on install: it stops WordPress keeping the 6000-pixel photograph somebody dragged in from a phone. Everything else — format conversion, fixing the images already in your library — is opt-in.

Install#

Once the listing exists, the plugin installs the way every WordPress plugin does: Plugins → Add New, search, activate. If you work from the command line:

wp plugin install subset-image-resizer --activate

There is no licence key for the free version and no account to create. The Pro add-on is a second plugin installed alongside this one; it does not replace it.

Set the two numbers that matter#

Open Settings → Image Resizer (placeholder — not final) and set a maximum width and a maximum height in pixels. An upload larger than either is scaled down, keeping its aspect ratio, before the original is written to disk.

Two things worth knowing about that:

• It applies to the original, not just the thumbnails. WordPress generates thumbnails at registered sizes and keeps the full-size upload as well. The full-size upload is usually the whole problem, and it is what this caps.
• It is not retroactive. Existing images are untouched until you run a regeneration pass, which is deliberate: a destructive default on somebody’s photo archive is not a default.

A sensible starting point is the widest your theme’s content column ever gets, doubled for high-density screens. For most sites that is somewhere around 2560 pixels on the long edge, and if you are unsure, larger is the safer mistake.

Check that it worked#

Upload a photograph you know is oversized, then look at the media library entry. The file dimensions shown should be your cap rather than the camera’s.

If they are not, the usual cause is another plugin also filtering the upload and running after this one. A diagnostics panel that names the other filter (placeholder — not final) is planned for the first release.

What to read next#

The bulk regeneration page covers fixing a library that is already full of oversized images, which is the reason most people install this. Updates and licensing explains what happens when a Pro licence lapses — the short version is that nothing stops working.