Historical kana browser setup

Use GenSeki Hentaigana Gothic Regular and Bold for historical kana, including the seven additions in Unicode 18. The font must be installed in Windows.

Chrome and Vivaldi

Install or update the userscript · version 0.2.0

This update fixes font ordering on Japanese Wikipedia's Small Kana Extension chart. Historical kana use GenSeki; ordinary text keeps the page's fonts.

Open the install link above and choose Update or Install in Tampermonkey.
If the link shows plain source code, open the existing Historical kana font fallback script in Tampermonkey's dashboard, replace its contents with the code below, and press Ctrl+S. For a first installation, choose Create a new script.
If Tampermonkey requests permission to run scripts, enable Allow User Scripts on its extension details page. See the official instructions.
Reload the affected web page.

// ==UserScript==
// @name         Historical kana font fallback
// @namespace    urn:historical-kana:font-fallback
// @version      0.2.0
// @license      MIT
// @description  Display historical kana using installed GenSeki Hentaigana Gothic, restricted to their Unicode ranges.
// @match        https://*/*
// @match        http://*/*
// @grant        GM_addStyle
// @run-at       document-start
// ==/UserScript==

(() => {
  'use strict';

  const family = 'Historical Kana Local Fallback';
  const ranges = 'U+3099-309A,U+1B000-1B128,U+1B132,U+1B150-1B152,' +
    'U+1B155,U+1B164-1B168,U+2A708,U+2CEFF,U+2CF00,U+2CF02';
  const historical = /[\u{1B000}-\u{1B128}\u{1B132}\u{1B150}-\u{1B152}\u{1B155}\u{1B164}-\u{1B168}\u{2A708}\u{2CEFF}\u{2CF00}\u{2CF02}]/u;

  GM_addStyle(`
    @font-face {
      font-family: "${family}";
      src: local("GenSeki Hentaigana Gothic"), local("GenSekiHentaiganaGothic");
      font-weight: 400;
      font-style: normal;
      unicode-range: ${ranges};
    }
    @font-face {
      font-family: "${family}";
      src: local("GenSeki Hentaigana Gothic Bold"), local("GenSekiHentaiganaGothic-Bold");
      font-weight: 700;
      font-style: normal;
      unicode-range: ${ranges};
    }
  `);

  function apply(element, text) {
    if (!element?.style || !historical.test(text)) return;
    if (element.matches('input[type="password"]')) return;
    if (element.closest('script, style, noscript, template')) return;
    const original = getComputedStyle(element).fontFamily;
    if (original.includes(family)) return;
    // A generic family can select a missing-glyph face before later fonts.
    // The Unicode range keeps this priority limited to historical kana.
    element.style.setProperty('font-family', `"${family}", ${original}`, 'important');
  }

  function visit(root) {
    if (root.nodeType === Node.TEXT_NODE) {
      apply(root.parentElement, root.nodeValue || '');
      return;
    }
    const walker = document.createTreeWalker(root, NodeFilter.SHOW_TEXT);
    while (walker.nextNode()) apply(walker.currentNode.parentElement, walker.currentNode.nodeValue || '');
    const inputs = 'input:not([type="password"]), textarea';
    if (root.matches?.(inputs)) apply(root, root.value || '');
    root.querySelectorAll?.(inputs).forEach(element => apply(element, element.value || ''));
  }

  const pending = new Set();
  let scheduled = false;
  function schedule(root) {
    pending.add(root);
    if (scheduled) return;
    scheduled = true;
    requestAnimationFrame(() => {
      scheduled = false;
      for (const node of pending) if (node.isConnected) visit(node);
      pending.clear();
    });
  }

  function start() {
    visit(document.body);
    new MutationObserver(records => {
      for (const record of records) {
        if (record.type === 'characterData') schedule(record.target);
        else record.addedNodes.forEach(schedule);
      }
    }).observe(document.body, {subtree: true, childList: true, characterData: true});
    document.addEventListener('input', event => {
      if (event.target.matches?.('input[type="password"]')) return;
      if (typeof event.target.value === 'string') apply(event.target, event.target.value);
    }, true);
  }

  if (document.body) start();
  else document.addEventListener('DOMContentLoaded', start, {once: true});
})();

The helper fills historical-kana gaps in a page's font stack. Other characters keep using the page's existing fonts. It runs locally and makes no network requests.

Firefox

Append GenSeki Hentaigana Gothic to the existing values of these string preferences in about:config. Keep existing font names and their order. Create an absent preference as a string containing the family name.

font.name-list.serif.ja
font.name-list.sans-serif.ja
font.name-list.monospace.ja
font.name-list.serif.x-unicode
font.name-list.sans-serif.x-unicode
font.name-list.monospace.x-unicode

Fully exit and reopen Firefox after installing fonts or configuring user.js.

Preview on this page

The left column requests Noto Sans JP and sans-serif; the right column requests GenSeki. The button below enables the helper for this preview. This preview does not install the userscript or check whether it is enabled on other websites.

Sample	Page font with fallback	GenSeki reference
Hentaigana	𛀁𛀂𛀃𛀆𛀋𛁒𛂋	𛀁𛀂𛀃𛀆𛀋𛁒𛂋
Small Kana Extension	𛄲𛅐𛅑𛅒𛅕𛅤𛅥𛅦𛅧𛅨	𛄲𛅐𛅑𛅒𛅕𛅤𛅥𛅦𛅧𛅨
Unicode 18	𛄣𛄤𛄥𛄦𛄧𛄨𛅨	𛄣𛄤𛄥𛄦𛄧𛄨𛅨
Combining marks	𛀂゙ 𛂩゚	𛀂゙ 𛂩゚
Mixed text	ABC かな漢字 𛀂𛄣	ABC かな漢字 𛀂𛄣

All 286 hentaigana

𛀁𛀂𛀃𛀄𛀅𛀆𛀇𛀈𛀉𛀊𛀋𛀌𛀍𛀎𛀏𛀐𛀑𛀒𛀓𛀔𛀕𛀖𛀗𛀘𛀙𛀚𛀛𛀜𛀝𛀞𛀟𛀠𛀡𛀢𛀣𛀤𛀥𛀦𛀧𛀨𛀩𛀪𛀫𛀬𛀭𛀮𛀯𛀰𛀱𛀲𛀳𛀴𛀵𛀶𛀷𛀸𛀹𛀺𛀻𛀼𛀽𛀾𛀿𛁀𛁁𛁂𛁃𛁄𛁅𛁆𛁇𛁈𛁉𛁊𛁋𛁌𛁍𛁎𛁏𛁐𛁑𛁒𛁓𛁔𛁕𛁖𛁗𛁘𛁙𛁚𛁛𛁜𛁝𛁞𛁟𛁠𛁡𛁢𛁣𛁤𛁥𛁦𛁧𛁨𛁩𛁪𛁫𛁬𛁭𛁮𛁯𛁰𛁱𛁲𛁳𛁴𛁵𛁶𛁷𛁸𛁹𛁺𛁻𛁼𛁽𛁾𛁿𛂀𛂁𛂂𛂃𛂄𛂅𛂆𛂇𛂈𛂉𛂊𛂋𛂌𛂍𛂎𛂏𛂐𛂑𛂒𛂓𛂔𛂕𛂖𛂗𛂘𛂙𛂚𛂛𛂜𛂝𛂞𛂟𛂠𛂡𛂢𛂣𛂤𛂥𛂦𛂧𛂨𛂩𛂪𛂫𛂬𛂭𛂮𛂯𛂰𛂱𛂲𛂳𛂴𛂵𛂶𛂷𛂸𛂹𛂺𛂻𛂼𛂽𛂾𛂿𛃀𛃁𛃂𛃃𛃄𛃅𛃆𛃇𛃈𛃉𛃊𛃋𛃌𛃍𛃎𛃏𛃐𛃑𛃒𛃓𛃔𛃕𛃖𛃗𛃘𛃙𛃚𛃛𛃜𛃝𛃞𛃟𛃠𛃡𛃢𛃣𛃤𛃥𛃦𛃧𛃨𛃩𛃪𛃫𛃬𛃭𛃮𛃯𛃰𛃱𛃲𛃳𛃴𛃵𛃶𛃷𛃸𛃹𛃺𛃻𛃼𛃽𛃾𛃿𛄀𛄁𛄂𛄃𛄄𛄅𛄆𛄇𛄈𛄉𛄊𛄋𛄌𛄍𛄎𛄏𛄐𛄑𛄒𛄓𛄔𛄕𛄖𛄗𛄘𛄙𛄚𛄛𛄜𛄝𛄞

The userscript applies to ordinary HTTP and HTTPS page text. Browser interface pages, PDF viewers, canvas text and shadow roots need their own font support.

Userscript file · Setup notes · Script licence