WordPress UTF-8 Text Handling

WordPress 6.9 modernized UTF-8 handling. New code should prefer the explicit UTF-8 helpers instead of older heuristics and hand-written byte regexes.

This skill is for server-side plugin text processing. It is not about block editor text controls.

When to use this skill

Trigger when ANY of the following is true:

• Code uses seems_utf8(), mb_check_encoding(), iconv(), utf8_encode(), utf8_decode(), or byte-level regexes.
• A plugin imports or exports CSV, XML, feeds, JSON, email, AI prompt data, logs, filenames, or third-party API text.
• The task mentions invalid UTF-8, mojibake, replacement character �, XML generation, REST encoding errors, or noncharacters.

The core helpers