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Translate & Lookup

Readest can translate a selection, look up a word in Wiktionary, or pop up the Wikipedia article — all without leaving the page.

Translate a selection

Select any text and pick Translate from the annotation toolbar, or press Ctrl+T / Cmd+T. A popup shows the translation alongside the original. You can copy either side, or dismiss the popup and keep reading.

Readest auto-detects the source language. Pick the target language from the popup; Readest remembers your last choice per book.

Translations are ephemeral by default — they disappear when you dismiss the popup. To keep one, annotate the selection first (Ctrl+N) and paste the translation into the note.

Translation providers

Switch provider under Settings → Language → Translation Service, and pick the target language under Translate To.

  • DeepL — widely considered the most natural-sounding translator for European languages.
  • Azure Translator — solid all-around choice with a large language catalog.
  • Google Translate — good for a wide variety of languages, especially outside Europe.
  • Yandex Translate — another built-in option, useful for Russian and nearby languages.

Daily usage limits apply to cloud providers. Readest shows remaining quota on the settings screen; if you hit a limit, switch to a different provider or wait for the daily reset.

Custom translators

Bring your own translation backend under Settings → Language → Custom Translators. Tap Add Translator and pick a Type:

  • OpenAI Compatible — any service that speaks the OpenAI API: OpenAI, DeepSeek, OpenRouter, SiliconFlow, Gemini, or a local server such as Ollama or LM Studio. Enter the Base URL, API Key (optional for local servers), and Model. Fetch Models lists what the server offers, and Temperature is optional.
  • DeepL — your own DeepL API key, Free (keys ending in :fx) or Pro. Available in the installed apps only, not on the web.

Tap Test to try a sample translation before you Save. Saved translators show up in the Translation Service list next to the built-in ones and work everywhere Readest translates: the selection popup and whole-book translation. Requests go straight from your device to the provider, so they don't count against Readest's daily translation quota.

Prompts. AI translators follow a prompt from the Prompts list on the same page. The built-in Default prompt is read-only; tap Add Prompt (or Duplicate an existing one) to write your own. Prompts can use the placeholders {{sourceLang}}, {{targetLang}}, {{bookTitle}}, and {{bookAuthor}}, and Readest appends the output-formatting rules itself. When an OpenAI-compatible translator is selected, a Prompt row appears under Translation Service so you can choose a prompt per book.

Custom translators need Plus, Pro, or the one-time Full Customization unlock. Without one, the Custom Translators row shows a Premium badge and saved custom translators are listed as unavailable, so translation falls back to a built-in provider.

Dictionary & Wikipedia

Dictionary. Select a single word and press Ctrl+D / Cmd+D, or tap Dictionary in the annotation toolbar. Readest looks the word up across every enabled provider — Wiktionary, Wikipedia, any custom dictionaries you've imported, and any web search providers you've added — and shows the results as a stack of cards. Tap a card header to expand or collapse it. If the exact word isn't found, Readest automatically retries with its base form, so looking up running or mice still turns up run and mouse (English today).

Wikipedia. Select a word or phrase and press Ctrl+W / Cmd+W, or tap Wikipedia. A Wikipedia article summary opens in a popup.

Both lookups follow the book's language, not your interface language. A Spanish book searches es.wikipedia.org, and Wiktionary reads the definition from the Spanish edition, es.wiktionary.org, so the explanation is written in Spanish too. When that edition is unreachable or has no entry, Readest falls back to English Wiktionary.

Custom dictionaries

Wiktionary and Wikipedia are built in. Beyond those, you can plug in your own dictionary files or any web-based dictionary or search engine.

Open the manager from Settings → Language → Dictionaries, or tap the gear icon at the top of any dictionary popup.

System Dictionary. At the top of the providers list, turn on System Dictionary to hand lookups to your operating system's own dictionary instead of Readest's in-app popup — the macOS Look Up panel, the iOS / iPadOS dictionary sheet, or Android's "process text" chooser (which offers whatever dictionary or translation apps you have installed). It's available on macOS, iOS, iPadOS, and Android (not on web, Windows, or Linux), and it's off by default. While it's on, the other providers are locked, since every lookup goes straight to the OS.

Offline bundles. Tap Import Dictionary and select all the bundle files together — large dictionaries now import and look up much faster. Supported formats:

  • StarDict — .ifo, .idx, and .dict.dz (optional .syn).
  • MDict — .mdx, with optional .css and one or more .mdd resource files. Companion .mdd files that share the .mdx name (Name.mdd, Name-01.mdd, …) are attached automatically — just select them all together.
  • DICT — .index plus .dict.dz (a raw, un-zipped .dict also works).
  • Slob — .slob.
  • Babylon — a single .bgl glossary.
  • Yomitan — a Yomitan-format .zip containing index.json and its term banks, or a portable pre-indexed .rdict. Import the file directly; structured entries, tags, links, and bundled images render in Readest's dictionary cards.

Imported bundles appear in the providers list. Drag to reorder, toggle on/off, rename, or delete.

Web Search. Tap Add Web Search to add any URL-based lookup. Give it a name and a URL template that contains %WORD% — Readest substitutes the selected word at lookup time. Examples:

  • https://www.google.com/search?q=%WORD%
  • https://www.merriam-webster.com/dictionary/%WORD%
  • https://dict.naver.com/search.dict?query=%WORD%

Web Search results open inline in the same stacked-card view.

Context dictionary

A word's dictionary entry lists every sense; the Context Dictionary tells you which one the author means. It explains the selected word or phrase as it's used in the surrounding passage: the sense meant here, pronunciation, part of speech, a short explanation, examples, and synonyms. It appears as one more card in the dictionary popup.

It runs on one of your OpenAI-compatible custom translators, so there's no separate AI setup:

  1. Add an OpenAI-compatible translator under Settings → Language → Custom Translators.
  2. Open Settings → Language → Manage Dictionaries and turn on Context Dictionary. It's off by default, since every lookup spends your own API tokens.
  3. If you have more than one AI translator, choose which one it uses under Context Dictionary → AI Translator.

Readest sends the selection's paragraph plus the paragraph on either side. The explanation comes back in your Translate To language, while headwords, examples, and synonyms stay in the book's language. If the request fails (a bad key, an exhausted quota, a wrong model name), the card shows the error. Like custom translators, the Context Dictionary needs Plus, Pro, or Full Customization.

Whole-book translation

For extended passages, or a whole book in a language you're learning, enable book translation mode from the reader menu. This translates paragraphs inline as you scroll, showing the translation below each original paragraph.

Notes:

  • Network-bound: every new paragraph sends a request to your chosen translation provider.
  • Respects your provider setting. Book-translate makes many requests, so high-quality translators with generous daily quotas (DeepL Pro, AI Gateway) suit it best.
  • Reading position and annotations still work the same — only the display changes.

Turn it off again from the same menu when you want to read monolingually.

Style the translation. The Translated Text group under Settings → Language sets how translated paragraphs look: Font (the book's own, or the reader's serif, sans-serif, or monospace font), Font Style (normal, italic, bold, or bold italic), Font Size relative to the paragraph, and Text Color. Left on their defaults, translations match the book's styling.

Word Lens

Word Lens prints a small native-language hint above the words it reckons are hard for you, so you can stay in the original language and only glance up when you need to. The hints render as ruby text above each word — like Japanese furigana, but for meaning.

Turn it on under Settings → Language → Word Lens:

  • Enable Word Lens — the master switch (set per book).
  • Level — your reading level on the CEFR scale (A1–C2). A lower level hints more words; a higher one hints only the rarest.
  • Language — the language the hints appear in (Auto follows your interface language).
  • Hint size and Hint color — style the gloss above the word.

Hints come from small per-language data packs. With Auto-download on (the default), Readest fetches the pack it needs over an unmetered connection; otherwise grab it yourself from the Data pack row. Word Lens works wherever the source language can be split into words — Chinese and space-separated languages are supported; Japanese, Korean, and Thai are not.

English-to-Vietnamese and English-to-Hungarian gloss packs are included alongside the existing Word Lens packs.