The per-directory configuration file.
WHAT IT CONTROLS
URL rewriting Redirects Access restrictions Custom error pages Compression and caching headers PHP settings, on some configurations Blocking specific files or user agents
WHERE IT GOES
In the directory it should affect. Rules in public_html apply site-wide; rules in a subdirectory apply there and below.
ORDER MATTERS
Rules are processed in order. A catch-all rewrite early in the file prevents later rules from being reached.
Place redirects above application blocks. In WordPress, above the BEGIN WordPress marker, or re-saving permalinks overwrites them.
BEFORE EDITING
Copy the file. A syntax error takes the entire site offline with a 500 error, and the file is frequently the last place people look.
TESTING
Load the site immediately after saving. If you get a 500, the file is the cause; restore your copy.
EXCLUDING THE SSL VALIDATION PATH
Add a condition excluding /.well-known/acme-challenge/ above your redirect rules, or certificate renewal fails.
PERFORMANCE
Rules are evaluated on every request. Keep the file short.
