Everything about Themes

One 3000 by 2000 photo becomes eight files on disk. A 1200 by 800 photo becomes five. Drop your own file in and see exactly which registered sizes fire, which ones core refuses, what dimensions come out and what the whole set weighs.

A 4032 pixel phone photograph in a 760 pixel column makes the browser download 12.2 million pixels to paint about 430,000 of them. What that costs in bytes and in memory, how to read the display width your theme actually uses, where the WordPress 2560 pixel safety net stops, and a browser tool that does the resizing before the upload.

A complete register_post_type() snippet you can paste into a one-file plugin, plus an honest walk through the arguments that change real behaviour: why the block editor refuses to load without show_in_rest, and why every new single URL returns a 404 until the rewrite rules are flushed.

A slot measured in CSS pixels needs a file measured in image pixels, and on a Retina screen the second number is twice the first. Here is how to measure the slot, choose a ratio without losing half the photograph, and check that WordPress will actually generate the size you need.

WooCommerce shows the same photograph in three places using three different files. Here are the three registered sizes, the cropping option that decides what happens to a mixed range, and why changing a width appears to do nothing.

One upload becomes eight or more files. Here is what WordPress actually creates, why some sizes are missing, and what to do about it, with numbers measured on a real site.

WordPress has added loading="lazy" itself since 5.5, and it skips the first three media elements on purpose, because the top one is usually the largest contentful paint element. Here is the real mechanism: the functions, the threshold of 3, fetchpriority, and the places where the logic never runs.

Every file you upload to WordPress gets a permalink, a template and a comment form. Here is the mechanism underneath attachment pages, what core changed in 6.4, and the correct way to redirect them.

A white screen with no error message isn't a WordPress bug. It's PHP dying silently mid-request. Here's how to see the real error in minutes and the exact order to check plugins, theme, and memory limits.

WordPress performance advice is usually handed over as a flat, alphabetized checklist. This walks through the same fixes in the order they actually pay off, starting with the thing most sites get wrong first: images.