A few lines in a file most people never open, deciding what your server does before WordPress is even loaded. These articles cover the directives that matter, and the ones that do nothing at all on your host.
Security & Privacy
WordPress File Permissions: 644, 755 and When Something Else
chmod 777 makes the error disappear by handing write access to every process on the server. What the three digits mean, the standard WordPress set, and why ownership decides which digit even gets read.
Rewrite Rule Tester: What Happens Between the URL and WP_Query
Between the URL bar and WP_Query sits an ordered array of regular expressions, 247 of them on this blog, stored in a single option row. Paste yours in, walk a request path down them, and see which rule wins, what query it builds and why the 404 happens.
Permalink Structure Simulator: What That One Field Decides
The permalink field decides thirteen URL shapes at once, and most of them fail quietly when you change it. What each structure tag costs, what verbose page rules actually do, which collisions core resolves first, and which old URLs its canonical redirect will never rescue.
WordPress Maximum Upload Size: Where the Limit Really Lives
The media library says 8 MB, the file is 12 MB, and nothing you edit in WordPress moves the number. It is not a WordPress setting at all: core reads two PHP directives and prints the smaller one. Which limit is really stopping the upload, why post_max_size is usually the culprit, how to raise the limits in the order that works, and why a photograph almost never needs a bigger ceiling.
Allowed Memory Size Exhausted: Where the WordPress Memory Limit Lives
The "Allowed memory size exhausted" fatal error involves three separate ceilings, and the one most people raise is not the one that stopped the request. How PHP's memory_limit, WP_MEMORY_LIMIT and WP_MAX_MEMORY_LIMIT interact, and why images trigger the error more often than anything else.
Redirect Rule Generator: The Rules That Never Fire
A redirect list rarely breaks. It accumulates: a broad prefix rule that kills every rule below it, a target missing a trailing slash that doubles your hop count, a 301 where a 308 was needed. Generate the Apache, nginx and CSV versions of your rules, then walk a URL through them and watch where it actually goes.
Stopping WordPress Hotlinking Without Breaking Image Search
Hotlinking is another site's HTML pointing at your image URL, so your server pays for their page. Prove it from the access log before you block anything, then write a referrer rule at the web server level that still lets crawlers, CDNs and link previews through.
Every WordPress site on Apache has an .htaccess, and Apache reads it on every request for every directory in the path. Here is what the WordPress block actually does, why [L] does not mean last, the difference between Redirect and RewriteRule, and which pasted security snippets have done nothing since Apache 2.4.
