About this plugin
This is a souped-up version of the Normalizer plugin by Torsten Landsiedel.
It adds WP filters to normalize UTF-8 data coming into the system to the de facto web standard Normalization Form C. The Unicode Consortium report is at Unicode Normalization Forms.
Polyfills
For best performance install (if possible) the PHP Internationalization extension Intl, which includes the PHP class Normalizer.
However the plugin works without the PHP Intl extension being installed, as it uses (a modified version of) the Symfony Normalizer polyfill.
Also text pasted into (most) inputs is normalized immediately using the JavaScript normalize() method. For browsers without normalization support, the unorm polyfill is used.
Background
For further info, see the WP Trac ticket #30130 Normalize characters with combining marks to precomposed characters and this Make WP Core comment.
The plugin also works around the Safari-specific issues raised by the WP Trac ticket #22363 Accents in attachment filenames should be sanitized.
Scanner
For existing data, the plugin includes an administration tool to scan and normalize the database. Important: before using this tool to normalize, please backup your database. This is especially important if your database contains non-normalized serialized data, as this plugin uses the same suck-and-see technique as interconnect/it’s Database Search and Replace Script in PHP to deal with serialized data, and is fallible.
And
A google-cheating schoolboy French translation is supplied.
1.
The project is on github.