Uploading Images: Best Practice for File Size

Large, unoptimised images are one of the most common causes of a slow website — often more impactful than anything else on the page. A few simple habits before and during upload make a big difference.

Before You Upload

• Resize the image to roughly the size it will actually display at. There’s rarely a need to upload something 4000 pixels wide for a thumbnail that will only ever show at 400 pixels — the extra resolution is invisible to visitors but still has to be downloaded by their browser, slowing the page down for no benefit.
• Save as a compressed JPEG for photos, or PNG only when you specifically need transparency (e.g. a logo on a coloured background). PNGs are generally much larger than JPEGs for photographic content, so using PNG by default for everything is a common cause of bloated pages.
• Aim to keep most web images under roughly 200–300KB where possible. As a rough guide, a well-compressed photo at typical display size should comfortably sit in this range — if a single image is several megabytes, it almost certainly hasn’t been resized or compressed yet.
• Consider the image’s purpose. A large hero banner at the top of a page can justify a slightly bigger file than a small thumbnail in a listing — but even hero images rarely need to exceed a few hundred KB once properly compressed.

Uploading

1. Go to Media → Add New, or upload directly from within a block when adding an image (e.g. clicking Upload inside an Image block).
2. Drag and drop the file, or click to browse and select it from your computer.
3. Wait for the upload and any automatic processing to finish before using the image. WordPress typically generates several resized versions automatically (thumbnail, medium, large, etc.) — this happens in the background right after upload, so give it a moment before assuming something’s gone wrong if the image doesn’t appear instantly.

Why This Is Worth the Extra Minute

• Page speed affects visitors directly — slow-loading pages are more likely to be abandoned, especially on mobile connections.
• Search engines factor in page speed when ranking results, so consistently oversized images across a site can have a knock-on SEO cost, not just a user experience one.
• It compounds. A single oversized image might not be noticeable, but a news listing page showing twenty unoptimised thumbnails at once can make a page feel sluggish even on a fast connection.

A Quick Habit to Build

Before uploading, glance at the file size shown by your computer’s file browser. If it’s several MB and the image is going to display as anything smaller than a full-width banner, it’s worth compressing first rather than uploading as-is and hoping WordPress handles it.

Tip: There are free tools (like Squoosh or TinyPNG) that compress images directly in your browser before you upload — no software to install. It only takes a minute per image and can dramatically cut file size with barely any visible quality loss. Making this a standard step before every upload, rather than an occasional afterthought, is the single biggest habit change that keeps a site’s media library lean.