Listen (TTS)

Readest can read any book out loud. TTS works on every platform, with an option to choose between on-device voices and higher-quality cloud voices. Playback continues in the background with lock-screen controls.

Start TTS

In the reader, tap the headphones icon in the bottom toolbar (tap the middle of the page first if the toolbars are hidden). With a hardware keyboard, the T key toggles it too. Playback starts from the current paragraph and continues through the chapter.

A mini player appears at the bottom of the page with play / pause, previous / next sentence, and stop. Tap the cover or title in the mini player to open the full Read Aloud player, which is where you change the voice, speed, and sleep timer.

Playback controls:

Action	Shortcut
Play / Pause	`Space`
Next sentence	`Ctrl+]` / `Cmd+]`
Previous sentence	`Ctrl+[` / `Cmd+[`
Next paragraph	`Ctrl+Shift+}` / `Cmd+Shift+}`
Previous paragraph	`Ctrl+Shift+{` / `Cmd+Shift+{`

You can also read aloud a selection only — select text in the reader and press Ctrl+R / Cmd+R. Readest reads the selection and stops.

Lock-screen controls and system media keys work on iOS, Android, macOS, and Windows — pause and skip without opening the app.

TTS engines

Readest ships three engines.

Native (system) TTS — uses the operating system's built-in voices. Fully offline, instant response, on Android and iOS (iOS uses Apple's on-device speech engine). Desktop native voices aren't wired up yet — on macOS, Windows, and Linux, use Edge TTS or the Web Speech voices in the web app.
Web Speech API — browser-based TTS when running in the web app. Depends on what the browser exposes.
Edge TTS — cloud-synthesized neural voices from Microsoft Edge's TTS. High quality, natural-sounding, many languages. Requires a network connection and sends the current sentence to Microsoft's servers for synthesis.

Edge TTS is the default whenever the device is online — on iOS and Android too. Readest doesn't switch to the system voices on its own: pick one from the System TTS group in the voice picker, and Readest remembers that choice per language from then on.

If you'd rather keep everything on-device, pick a voice from the System TTS group.

Voices & languages

Choose a voice. While TTS is playing, open the full Read Aloud player (tap the cover or title in the mini player) and tap Voice. Voices are grouped by engine — Edge TTS cloud voices and, on iOS and Android, System TTS on-device voices — and filtered by the language of the current book. Picking a voice also switches to its engine, and the choice is remembered per language. Voice and engine selection live here, not under Settings → TTS, which only covers highlighting, media info, and the audio cache.

Readest automatically switches voices when a book contains multiple languages, so a bilingual edition uses the right voice for each passage.

To add more voices:

Android — system TTS settings, installed engines (Google TTS, Samsung TTS, etc.).
iOS / iPadOS — the System TTS group lists Apple's on-device voices; download more under iOS Settings → Accessibility → Spoken Content → Voices. Readest picks its own default from that list rather than the voice chosen in iOS settings, so select the one you want once in the voice picker.
macOS / Windows / Linux — no native voices yet; use Edge TTS (cloud) or, in the web app, the browser's Web Speech voices.

Newly installed voices show up in Readest the next time you open the voice picker.

Speed & controls

Speed — 0.5× to 3×, in fine increments. The default is 1×.
Sleep timer — stop at the end of the current chapter or after a duration from 1 minute to 8 hours.

Speed changes take effect immediately — mid-sentence if needed.

Sentence highlighting

While TTS plays, the text being read is highlighted in the book. Settings under TTS → Highlighting let you tune:

Granularity — highlight the whole Sentence, or just the single Word as it's spoken (the default). Word-by-word read-along needs an engine that reports word timings — Edge TTS and the Web Speech voices do; the on-device Native voices highlight by sentence. CJK text also highlights by sentence.
Style — highlight, underline, strikethrough, squiggly or outline.
Color — the highlight color.

Want to keep a line you just heard? Press Shift+M to save the sentence TTS is currently reading as a permanent highlight (using your default highlight style and color) — no need to select it by hand.

In paginated mode, Readest auto-advances the page when the reader crosses the edge of the visible content. In scrolled mode, the view scrolls smoothly to keep the currently-spoken sentence in view.

When the active engine can align audio to text, the expanded Read Aloud player shows a lyric-style transcript centered on the current sentence. Scroll to another sentence and press play to continue from there.

For pronunciation fixes (e.g., making TTS read "LLM" correctly), see Proofread rules — rules can be scoped to TTS-only so they don't touch the visible book text.

Offline audio

With a paid Readest plan and a download-capable TTS voice, open the expanded Read Aloud player and choose Offline Audio. Download one chapter or Download all; each row shows whether it is waiting, downloading, partial, failed, or ready offline.

The queue is saved per book, so you can close and reopen the player without losing it. Tap a queued chapter to cancel it, retry a partial or failed chapter, or use Clear all to remove the downloaded speech and reclaim its displayed storage size.

Pair an audiobook

Readest can use a human-narrated audiobook as an ebook's read-along audio:

Open the ebook, then choose Book Menu → Pair Audiobook.
Select one .m4b file or a set of .mp3 / .m4a tracks in playback order. If you've connected Audiobookshelf, you can choose a title from that server instead and stream it without downloading.
Match one known ebook chapter to its audio chapter or track. Readest maps the remaining chapters sequentially.
Review the mapping, preview any chapter, and leave mismatches unpaired or adjust them manually.

After pairing, the normal Read Aloud player follows the narration with a timeline, 15-second back / 30-second forward controls, and audiobook chapter skips. Return to Book Menu → Manage Audiobook to edit the mapping, replace the audio, or remove the pairing.