Tools that answer one question honestly: is this what you think it is. Each article carries something that checks a file, a layout or a claim, and tells you where it fails rather than that it passed.
SEO & Structured Data
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.
Gutenberg Block Invalid Content: Validate and Repair Block Markup
The editor says a block contains unexpected or invalid content and stops there: no line, no attribute, no cause. Here is what it compared, why block markup drifts after a migration, and how to find the exact character that broke it.
JSON Validator and Repair: What the Parser Actually Saw
Parsers name the character after the mistake, and PHP names nothing at all. The whole JSON grammar, the invisible bytes that break a file that looks perfect, the places WordPress hides JSON, and a validator that reports every fault in one pass.
Serialized Data Repair and Search Replace: The Bytes That Break a Migration
One UPDATE with REPLACE() over wp_options is all it takes to kill a WordPress site after a migration, without printing a single error. The reason is a number baked into PHP's serialization format, and the fix is counting bytes.
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.
