How to install Noto Sans CJK fonts for reMarkable Tablet

Install CJK fonts to reMarkable Tablet.md

reMarkable is a paper tablet by https://remarkable.com/.

The reMarkable tablet is the best e-paper in the market. However, it does not have built-in support for CJK (Chiniese, Korean and Japanese) users.

Luckily, this could be resolved by installing CJK fonts on the tablet.

1. Go to Preference > Storage > Enable USB web interface (Beta).
2. Connect reMarkable with your PC via a microUSB cable.
3. SSH to the device as user "root" using the password find in Preference > About. e.g. ssh root@10.11.99.1
4. Download "NotoSansCJK[you language]-Regular.otf" from https://www.google.com/get/noto/help/cjk/ *note, there is limited space on the device, so do not sue "Super OpenType/CFF Collection (Super OTC)", an language-specific OTC is ok.
5. Copy (using SCP or whateever tools you like) to /usr/share/fonts/opentype/
6. Make sure the uploaded font file has the corrent permission (it should be 644).
7. Run fc-cache -f -v to refresh to font cache.
8. Reboot the device reboot. (or use the physical button)
9. Read a book in your language, set the font as "Noto Sans" in Text settings.
10. Done!

• Note: CJK Serif Fonts does not work even if I have installed OTF on the device and select Noto Serif, not sure why. Noto Sans is good enough though!

Install CJK Fonts to reMarkable Tablet (firmware 3.x, tested on 3.27.3.0)

Overview

Instructions for installing CJK (Chinese, Japanese, Korean) fonts on reMarkable tablets so ebooks display these languages properly. Tested on a reMarkable 1 running firmware 3.27.3.0.

⚠️ What changed on firmware 3.x: the root filesystem is nearly full (~11 MB free), so the old advice of copying fonts to /usr/share/fonts/ no longer works. Install fonts to /home/root/.local/share/fonts/ instead — it lives on the data partition (several GB free), xochitl picks it up automatically, and it survives both reboots and OS upgrades (upgrades replace the whole OS partition, but never touch /home).

Which font to download

Use the Subset OTF flavor from the notofonts/noto-cjk repo — it contains only the glyphs for one language, so a single weight is only ~5–6 MB (vs ~16 MB for the language-specific OTF, or 300+ MB for the Super OTC).

For Traditional Chinese, Regular + Bold is only ~11 MB total:

curl -LO https://github.com/notofonts/noto-cjk/raw/main/Sans/SubsetOTF/TC/NotoSansTC-Regular.otf
curl -LO https://github.com/notofonts/noto-cjk/raw/main/Sans/SubsetOTF/TC/NotoSansTC-Bold.otf

The TC subset covers the ~7,800 most frequent Traditional Chinese characters plus Taiwan's 常用國字標準字體表, Hong Kong's 常用字字形表, Bopomofo, and full-width punctuation — plenty for reading ebooks.

Other languages: swap TC for SC (Simplified Chinese), JP (Japanese), or KR (Korean) in the URLs. Prefer serif for reading? Use Serif/SubsetOTF/TC/NotoSerifTC-Regular.otf (~7 MB) from the same repo.

Steps

1. On the tablet, go to Settings > Storage and enable the USB web interface, then connect via USB cable.

2. Find the root password in Settings > General > Help > Copyrights and licenses (bottom of the GPLv3 section).

3. Create the user font directory and copy the fonts over (the -O flag is needed because the tablet has no SFTP server):

   ssh root@10.11.99.1 "mkdir -p /home/root/.local/share/fonts"
   scp -O NotoSansTC-Regular.otf NotoSansTC-Bold.otf root@10.11.99.1:/home/root/.local/share/fonts/

4. Fix permissions and rebuild the font cache (the cache is mainly for CLI tools — xochitl scans the directory itself — but it makes verification easy):

   ssh root@10.11.99.1 "chmod 644 /home/root/.local/share/fonts/*.otf && fc-cache -fv"
   ssh root@10.11.99.1 "fc-list | grep 'Noto Sans TC'"
   # /home/root/.local/share/fonts/NotoSansTC-Regular.otf: Noto Sans TC:style=Regular
   # /home/root/.local/share/fonts/NotoSansTC-Bold.otf: Noto Sans TC:style=Bold

5. Clear stale render caches — this is the step everyone misses. xochitl pre-renders each EPUB to a hidden <doc-uuid>.pdf next to the .epub and keeps serving it forever; books added before the font install will show tofu (□) no matter what you change, because the tofu is baked into an old cached render. Deleting the cache is safe — the document itself is untouched and re-renders on next open:

   ssh root@10.11.99.1 'systemctl stop xochitl
   cd /home/root/.local/share/remarkable/xochitl
   for e in *.epub; do rm -f "${e%.epub}.pdf" "${e%.epub}.epubindex"; done
   systemctl start xochitl'

   (This also restarts xochitl, so no reboot is needed. Avoid restarting xochitl more than a few times within 10 minutes — its systemd unit rate-limits starts, and exceeding the limit triggers the watchdog, which reboots the device.)

6. Open an ebook. On firmware 3.x the Text settings font picker is a hardcoded list (EB Garamond / Noto Sans / Noto Mono / Noto Serif) — installed fonts never appear in it, in any format. That's fine: pick any of them (or leave the publisher default) and CJK characters render through per-glyph fallback to your installed font.

How it works (and why old guides mislead)

• xochitl is launched by systemd without $HOME, so fontconfig CLI tools behave differently from xochitl itself — env -i fc-match "Noto Sans" can't see user fonts, which makes it look like fallback is broken. It isn't: xochitl is a Qt app, and Qt resolves the home directory via the passwd database, scanning /home/root/.local/share/fonts regardless of the environment. No /etc/fonts/local.conf, no systemd tweaks, no HOME hacks needed.
• Because nothing outside /home is involved, the setup survives reboots and OS upgrades. After an upgrade, at most re-clear the render caches of books that still show tofu (step 5).
• If one stubborn book still shows tofu, its per-book font is stored as "fontName" in /home/root/.local/share/remarkable/xochitl/<doc-uuid>.content ("" = publisher default). Stop xochitl, set it to your CJK family (e.g. "Noto Sans TC"), delete that book's .pdf/.epubindex cache, and start xochitl.
• Rare characters can still tofu legitimately: the TC subset omits Japanese-only kanji (e.g. 峠, 読). Add the JP subset font if you read mixed content.

Vertical reading (直排)

xochitl ignores EPUB writing-mode CSS, so real vertical layout is impossible — but 偽直排 (fake-vertical) fonts work perfectly: every glyph is pre-rotated 90° counterclockwise, so you render the book as normal horizontal text and physically rotate the tablet 90° clockwise to read top-to-bottom, right-to-left. Tested on 3.27.3.0.

Fonts (pick one):

Font	Style	Download	Size
源流明體 GenRyuMin TW	明體 (ming/serif)	GenRyuMinTW-Medium-R03-Simp2Trad.ttf (more variants + docs: vixual.net)	15 MB
原俠正楷 GuanKiapTsingKhai	楷書 (kai)	GuanKiapTsingKhai-TW-90.ttf (other variants: releases)	10 MB
懷源黑體 KaiGenGothic TW	黑體 (gothic/sans)	KaiGenGothicTW-Medium-R02-Simp2Trad.ttf	11 MB

Simp2Trad / -TW variants also convert simplified characters to traditional glyphs and Taiwan word conventions on the fly — handy for mainland-sourced EPUBs. (The GuanKiapTsingKhai author notes the auto-word-selection -W/-TW variants can rarely overlap characters; use -T-90 if you hit that.)

Install (same as the main steps — the font just goes in the user font dir):

scp -O GuanKiapTsingKhai-TW-90.ttf root@10.11.99.1:/home/root/.local/share/fonts/
ssh root@10.11.99.1 "chmod 644 /home/root/.local/share/fonts/*.ttf && fc-cache -f"

Apply to a book — the picker will never list the font (hardcoded list), so set it per book. Find the book's UUID by its title, then point its .content at the font's exact family name and clear the render cache:

# 1. find the UUID of your book (grep by title)
ssh root@10.11.99.1 'grep -l "書名" /home/root/.local/share/remarkable/xochitl/*.metadata'

# 2. get the exact family name fontconfig reports
ssh root@10.11.99.1 'fc-list | grep -i guankiap'
# → GuanKiapTsingKhai-TW-90

# 3. set the book to that family and force a fresh render
ssh root@10.11.99.1 'systemctl stop xochitl
cd /home/root/.local/share/remarkable/xochitl
id=<uuid-from-step-1>
sed -i "s/\"fontName\": \"[^\"]*\"/\"fontName\": \"GuanKiapTsingKhai-TW-90\"/" $id.content
rm -f $id.pdf $id.epubindex
systemctl start xochitl'

Open the book, rotate the tablet 90° clockwise, and read. The setting persists (reboots, upgrades, sync) — just never touch that book's font in Text settings, or the picker will overwrite it.

No-SSH alternative — embed the font in the EPUB itself: in Calibre, Convert book → Look & feel → Fonts → Embed font family with the rotated TTF (and let it set the base font), then upload the converted EPUB normally. Books left on the publisher default use their embedded fonts, so the vertical typography travels with the file — no device tweaks at all.

Caveats:

• Do not try the document's "orientation": "landscape" setting (or the UI landscape toggle) as a substitute for physically rotating the device — xochitl rotates landscape content the opposite direction, producing upside-down text (verified).
• Half-width Latin/numbers lie sideways in vertical reading — inherent to the trick.
• Serif CJK needs the explicit override. Per-glyph fallback does not style-match: with both Noto Sans TC and Noto Serif TC installed, selecting the built-in Noto Serif renders Latin in serif but falls back to the sans CJK font (verified by inspecting the render — it embeds NotoSerif + NotoSansTC). To read Chinese in serif (明體), either set the book's .content to "fontName": "Noto Serif TC" and clear its render cache as above, or — if you want serif everywhere with no per-book SSH — install only the Serif TC family: fallback can only pick from what's installed, so with a single CJK family present, every book uses it automatically.

https://github.com/chenhunghan/remarkable-cjk-fonts