tools.omikuji.dev

Desu/masu ⇔ Da/dearu Converter

Unify Japanese writing between polite (desu/masu) and plain (da/dearu) style in one click, both ways. Also detects mixed styles. This tool works on Japanese text only.

🔒 Your text is never sent anywhere (processed in-browser) Free, no sign-up
Mode
To plain: converts polite desu/masu endings into plain da/dearu (for reports & papers)
Paste Japanese text — this tool converts Japanese only 0 chars
Loading the conversion engine (kuromoji.js)… 0%
First time only: about 4MB of dictionary data (same site, nothing uploaded).
Running in simple mode — The conversion engine failed to load, so only the fixed sentence-ending dictionary is used. Verb conjugations (〜ます→〜る, etc.) are not converted. Reload to try to recover. Reload
Output
The converted text will appear here
This is a mechanical conversion. Always review the highlighted endings yourself.

How to use

  1. 1 Paste Japanese text
  2. 2 Pick a direction (da/dearu or desu/masu) or the check mode
  3. 3 Convert → review the highlighted endings → copy

Mechanical conversion leaves some unnatural sentences — always review the highlights. Text inside 「」 quotes is not converted by default. Everything is processed in your browser and never sent anywhere.

Features

Two-way conversion

Plain (da/dearu), the most common request for reports, is the default. One click also handles polite (desu/masu) for résumés and business writing.

Style-mix checker

Tallies polite and plain sentences and highlights the minority. Find style inconsistencies while proofreading.

Protects quoted speech

Text inside 「」 quotes is excluded by default. A toggle lets you convert inside quotes too.

Nothing ever leaves your browser

Bundles the dictionary and morphological analyzer (kuromoji.js) so processing stays in-browser — safe for résumés, papers and work documents.

Use cases

Unify reports and theses

Turn a polite-style draft into the plain (da/dearu) style required by reports and theses in one click.

Blog draft to résumé style

Quickly convert a polite blog draft into a clean style suited for résumés and applications.

Spot style drift (proofreading)

Use the style check to find, sentence by sentence, where polite and plain styles are mixed in a long text.

Make business writing polite

Turn plain-style notes into a polite (desu/masu) draft you can send externally.

Privacy

Conversion and style checking run entirely in your browser as pure client-side processing. Your text is never sent to or stored on any server, and the morphological-analysis dictionary also runs in-browser. It is safe to paste private text such as résumés, papers and work documents.

FAQ

Should reports be plain or polite style?

Academic reports and papers are generally required to be in plain (da/dearu) style. Follow whatever your assignment specifies. This tool defaults to plain-style conversion.

Can I submit the result as-is?

It is a draft. Mechanical conversion leaves some unnatural sentences, so always review the highlights. Endings, colloquialisms and inversions cannot be fully auto-converted.

Is my text uploaded anywhere?

No. Conversion and the style check are fully in-browser; not a single character reaches a server. The analysis dictionary also runs in your browser.

What happens to speech inside 「」 quotes?

It is not converted by default, matching the writing convention that quotes and dialogue are excluded from style conversion. Turn the toggle on to convert inside quotes too.

Text Tools Series

Keigo Converter →
To fix honorific and humble forms too, use the Keigo Converter. This tool only handles polite ⇔ plain sentence endings.
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The output is a draft; accuracy is not guaranteed. Always review before use.