The most common reason a site feels slow is not complicated code; it is photographs uploaded untouched. A modern phone photo often exceeds 4,000 pixels across, while the width actually used on screen is far smaller. The rest is downloaded and thrown away.
Happily, this takes about thirty seconds to fix before uploading. Three steps: size, format, filename.
1. Size — only as large as it is used
This is where the big saving lives. Look at how wide the image is actually displayed and resize it to roughly that before uploading. A full-width background needs generous dimensions; a photograph inside an article needs far less.
WordPress automatically generates several sizes from what you upload and serves an appropriate one. That helps a great deal, but an oversized original still costs you wherever the original is used, which is why resizing before upload remains worthwhile.
2. Format — photograph or graphic?
Format is decided by content, not preference. Photographs, with their smooth gradations, belong in the JPEG family; logos, icons and diagrams, made of lines and flat areas, belong in PNG or SVG. Save a logo as a JPEG and the edges of the lettering go muddy.
On top of that, a modern format such as WebP produces a smaller file at the same visual quality. Browser support is broad today, and the conversion can be automated with free tools or a plugin.
Logos that need a transparent background stay as PNG or SVG. An SVG logo in particular stays crisp at any screen density and weighs very little.
3. Filenames and alt text
Rename the file just before uploading. IMG_4821.JPG tells neither a person nor a search engine anything. Use lower-case Latin letters, hyphens and a description of the content: seoul-office-interior.jpg.
Filenames in non-Latin scripts are best avoided, since some server environments encode them into long or broken URLs.
After uploading, write the alt text. It is what a visitor using a screen reader hears, and it is how search engines understand the image. Do not write “photo” — describe in one sentence what can actually be seen.
How images affect first-screen speed is covered further in the performance archive, and if hundreds are already uploaded at full size, bulk cleanup is part of our optimization program.
Next part
Everything so far has been faster done yourself. The next part looks at the other side — the work that costs more when you do it, measured by the value of your own hours.