Redirect generator

The two mistakes this exists to prevent

An unescaped full stop. In a regular expression . matches any character, so a rule written for /pricing.html also matches /pricingXhtml. Harmless until it is not. Every pattern here is escaped.

A rule with no anchor. Apache's Redirect matches by prefix and cannot be anchored, so a rule for /shop also catches /shopping, /shop-faq and everything else beginning the same way. That is the failure you hear about from a customer rather than find yourself. RedirectMatch is anchored with ^ and $, which is why it is the default here.

The generator also refuses a URL that redirects to itself, and tells you when the same source appears twice - in which case the first rule wins and the second is dead weight.

Which style to use

Style	Use it when
RedirectMatch	Almost always. Anchored, escaped, exact.
Redirect	Moving a whole directory, where prefix matching is the point.
RewriteRule	You are already inside a mod_rewrite block, or need conditions.

Three things Apache will not do

A query string cannot be matched by a RedirectMatch or RewriteRule pattern. /?p=123 needs a RewriteCond %{QUERY_STRING} before the rule; the pattern itself only ever sees the path.

[L] does not mean "last" in a per-directory .htaccess. An internal rewrite re-runs the whole ruleset from the top, so a rule protected only by [L] can match its own output. Guard it with a RewriteCond instead.

A .htaccess in a subdirectory replaces its parent's rules rather than adding to them. A rule for /cms/... written in the web root simply does not run while WordPress ships its own file at /cms/.htaccess - which is why migration redirects for media so often appear to do nothing until the old install is finally removed.