Asteria Type it all, convert once.
らいげつからはじまる…しりょうをまとめます
→ 来月から始まる新しいプロジェクトの計画について部長と相談した結果…
Even 107 characters typed in one go are segmented and converted correctly with a single Space.
JAPANESE INPUT FOR WINDOWS · v4.0.0 STABLE
The word you meant,
with one Space.
Asteria reads long sentences and the sentence before, so the first candidate is the right one. Free and open source. Your text never leaves your PC.
- No account
- One-screen installer
- Windows 10 / 11 · about 1.7 GB
Free and open sourceYour text stays on your PCTyping never stops
Stop going back to fix conversions.
Spot the mistake, move back, pick another candidate — those seconds add up dozens of times a day. Asteria combines Mozc's dictionary conversion with AI running on your PC's GPU, and focuses on making the first candidate right.
Reads the sentence before.
週末は美術館で絵を かんしょうする
→ 鑑賞する (appreciate)
子どものけんかに親が かんしょうする
→ 干渉する (interfere)
Same reading, different word — chosen from context.
English stays English.
ぎっとはぶにれぽじとりを…
→ GitHubにレポジトリを…
GitHub and Zoom come out in English spelling, not katakana.
Compared with Google Japanese Input, under the same conditions.
274 vs 133
Homophones decided by the previous sentence (300 items)
461 vs 434
Everyday short sentences (500 items, spelling variants counted as equal)
Same PC, same typing; items not used for tuning; the first candidate after Space was counted. Asteria v3.0.0 (October 25, 2026) / Google Japanese Input 3.34.6260 (October 23). Asteria still errs on homophones that depend on meaning and on proper nouns. Method and full results →
One screen to install.
- Download and openAsteria64.msi (about 1.7 GB)
- Press “Install”Allow the Windows prompt; a completion screen confirms it is done.
- Pick it with Windows + SpaceChoose “Asteria日本語入力”.
It never asks you to close open apps. Updates from v3.0.0 onward need no restart (updating from v2.0.0 or earlier asks for one restart at the end). Uninstalling keeps what Asteria has learned, so reinstalling picks up where you left off.
Made to be used every day.
Text stays on your PC
The dictionary and AI ship inside the installer; conversion needs no network. In password fields, Asteria is built to stop reading context, AI and learning.
Never stuck
If the GPU is unavailable or AI is still loading, dictionary conversion keeps you typing.
Open to inspection
Source code, evaluation method and failure examples are public.
See your usage
The settings dashboard shows today's conversions, time to candidates and first-candidate rate — counts and times only.
FAQ
Is there live conversion?
From v4.0.0 you can turn it on in the “AI変換” settings tab (off by default). When you pause, the text turns into the AI conversion, and Enter commits it as shown. It is always the same as the first candidate you would get with Space. The same tab also offers homophone hints and an experimental option to run the AI on an integrated GPU.
Does it work without a GPU?
Yes, with the CPU-oriented Low setting. Quality and speed differ from Standard on a dedicated Vulkan GPU with at least 3 GiB VRAM.
Windows says “Windows protected your PC”.
The installer is unsigned, so SmartScreen may appear. Confirm it came from the official GitHub Release and check the attached SHA-256, then choose “More info → Run anyway”.
Why is it so large?
The AI models and runtime are bundled, so there is nothing else to install — no Python or CUDA setup.
Can I keep Google Japanese Input or Microsoft IME?
Yes. Switch any time with Windows + Space.
System requirements?
Windows 10 1809 or later / Windows 11 (x64), 8 GB RAM (16 GB recommended), about 1.7 GB disk. GPU AI uses a dedicated Vulkan GPU (NVIDIA / AMD / Intel Arc) with 3 GiB+ VRAM; integrated GPUs are not used.
Make everyday typing Asteria.
If you like it, a Star on GitHub is the best encouragement to keep going.