CastReader

Read it aloud. Then have it explained like a teacher.

Listen to the original or a plain-language explanation, with marks that point back to the source. On the Web, sign in and select an AI voice to explain one paragraph at a time.

Open the Web document toolAdd to ChromeGet the iOS or Android app

28 product languages · 3 Free explanations daily · Formats and controls vary by client

Illustrative passage · not a website quotation
Fixed animation
Spanish example→English explanation

El interés compuesto permite que los intereses acumulados generen nuevos intereses. El resultado depende de los tipos, el tiempo, las comisiones y las retiradas.

Compoundinterestisthecentralconcept.

1/31.0×

This fixed, silent animation illustrates how an explanation points back to the source; it is not live generation.

Cross-language illustration

This illustrates Spanish-to-English explanation. Web Explain follows the document language; other clients depend on their available language controls.

EspañolEnglishExample languages only

Guided Read-and-Explain

An explanation layer that stays connected to the source

Read & Explain brings spoken explanations, captions, and source marks together. Use it to understand a passage, then check the original: AI can miss or misinterpret information.

Inputs
Web: text-based PDF, DRM-free EPUB, DOCX, TXT, Markdown, HTML; webpage and OCR workflows depend on the client
Depths
Web uses Standard; other clients offer only the controls available in that client
Guidance
Spoken explanation, synced subtitles, highlighting, circles, and underlines
Best fit
Dense long-form material where the original context must stay visible

Read aloud vs. Read & Explain

CastReader Read speaks the original; Explain helps unpack the meaning of a passage.

Plain read-aloud
Device or AI voices
  • Reads the original text, word for word
  • Uses a voice suited to the source language
  • Paragraph-level highlight
  • You still have to make sense of it yourself
Read & ExplainCastReader's guided approach
 
  • Explains what the page means, in plain language
  • Web follows the document language; other clients depend on their language controls
  • A pen circles & underlines the exact key points
  • Like a teacher reading along beside you

One source, three levels of guidance

Compare fixed examples at three depths

Overview orients you, Standard explains the passage, and Deep illustrates closer analysis. These buttons switch examples only. Web currently uses Standard; other clients depend on their available controls.

Example source passage

Compound interest means your savings earn interest, and the accumulated interest can earn interest too. As the balance grows, each later period calculates returns from a larger base.

Illustrative output: Overview

Answer: What is this about, and what should I notice first?

The passage explains why compound interest can accelerate savings growth: returns are calculated not only on the original amount, but also on interest already added to the balance.

  • Main idea
  • Key conclusion
  • Important terms
  • Document structure

Best for: triage, previews, long reading queues, and deciding where to focus

Fixed examples, not live AI output. Actual explanations depend on the source, current paragraph, language, and available context.

Interactive Read & Explain Lab

See how the same depth changes across six kinds of reading

Compare prewritten examples by scenario and depth. This demonstration does not generate AI explanations; the Web file tool currently uses Standard depth only.

Choose the reading task

Source excerpt

Illustrative research result
In the preregistered trial, the intervention group improved by 8%, but the confidence interval included effects close to zero and the six-week follow-up had 18% attrition.

Choose an example depth

Guided explanation sample

Separate the effect estimate from the evidence quality

The 8% describes change within the intervention group, not a stated between-group difference. The interval mentions effects near zero, but the excerpt does not identify the corresponding estimate. With 18% attrition at six weeks, check how missing data were handled.

This example focuses on

  • Effect size
  • Confidence interval
  • Attrition bias
  • Short- vs long-term claim

Verify: Compare baseline balance, missing-data handling, and whether the primary outcome matches the registration.

Get a reading suggestion from passage length

Enter up to 1,500 characters. This simple demo suggests a depth from character count alone: it does not analyze meaning, choose your scenario, or change the actual tool settings.

Text in this box stays in the browser for a length check; it is not sent to AI.0/1500 characters

To generate an explanation, open the Web document tool, sign in, and select an AI voice. Web Explain uses Standard depth for one paragraph; it does not use this demo suggestion.

Open the Web document toolGet the Chrome extensionGet CastReader for iPhone or Android

Three things at once — like a teacher pointing at the page

Explanation, pen marks, and subtitles, all synced to the audio.

Explains, not just reads

Instead of reading the original sentence by sentence, it summarizes and unpacks the meaning — so dense, technical, or foreign pages finally click.

Marks the key points

Marks point to words being discussed, helping you compare the explanation with the original.

Subtitles you can follow

Follow the explanation captions while listening, and pause to check important details.

Cross-language understanding

Keep the foreign-language source visible as you explore its meaning

Understand unfamiliar-language text in your own language without losing the words, structure, and evidence in front of you.

A literal translation answers what the sentence says. Explain in My Language stays beside the original and adds the context, relationships, and implied meaning you need to follow it. The examples below use short excerpts from public sources so you can compare the two jobs directly.

Choose a fixed example

Original source

Botchan by Natsume Soseki

親譲りの無鉄砲で小供の時から損ばかりしている。

Explanation anchor: “親譲りの無鉄砲”

Open the public source

Aozora Bunko public-domain text. Short excerpt shown for study and attribution.

Literal translation

Answers: What do these words say?

Because of the recklessness inherited from my parents, I have done nothing but lose out since childhood.

Explain in my language

Answers: What does this mean here, and why?

The narrator opens by blaming an inherited, impulsive temperament for a lifetime of self-inflicted trouble. The line is comic and self-deprecating, but it also carries pride: he recognizes the consequences without presenting caution as the better way to live.

What the explanation adds

  • An inherited temperament frames the narrator
  • The voice is comic and self-deprecating
  • 損 means adverse consequences, not only financial loss
  • The tension between regret and pride matters

This is one reading of a literary opening, not a replacement for the novel or its ambiguity. Check surrounding passages and other translations when wording matters.

Use translation and explanation for different jobs

CastReader is a reading aid, not a certified translation service. Keep translation when exact wording is the deliverable; use source-anchored explanation when understanding is the obstacle.

日本語EspañolEnglish

The labels below identify languages used in these examples, not a complete support list. The public AI voice catalog covers 28 languages; Filipino, Hebrew, Indonesian, Malay, Romanian, Turkish, and Vietnamese remain Beta. Web Explain follows the document language and has no output-language selector. Cross-language settings depend on the client.

Your actual needBest workflow
Publish, quote, or submit exact wordingTranslation plus human review
Understand an argument, concept, or passageExplain in My Language
Learn from the source languageOriginal text, highlighting, and explanation together
Make a legal, medical, financial, or safety decisionQualified professional review

How to use Read & Explain

These steps apply to the Web document tool. Extension and app controls depend on their own interfaces.

1

Open a file

Open the document tool and choose a supported file. PDFs need a text layer; EPUBs must be DRM-free.

2

Sign in and select an AI voice

Sign in and select an AI voice. A selection spanning paragraphs uses the first intersecting paragraph; without a selection, Explain uses the current paragraph. Device voices do not support Explain.

3

Explain and verify

Choose Explain, listen to the Standard explanation, and check the source marks. Web follows the document language and has no depth or output-language selector.

Six explanation workflows

Different documents need different kinds of teaching

These scenarios illustrate reading approaches, not automatic analysis of an entire book or every file. Web Explain processes one paragraph at Standard depth. Webpage and image/OCR workflows depend on the client; Web files need extractable text.

Papers and academic reading

“Can you read this paper to me and explain the argument?”

Start with the research question and contribution, then stay anchored to the abstract, methods, results, and limitations while the explanation follows the paper's structure.

Read arXiv papers aloud

Common inputs

URLPDFDOCXImage/OCRText

Illustrative reading approach

Overview for paper triage; Standard for a first full pass; Deep for methods, arguments, and limitations.

What CastReader can help surface

  • Research question and contribution
  • Methods in plain language
  • Claim-to-evidence links
  • Limitations and terms to verify

CastReader can support comprehension, but it does not validate the research or replace the paper, its data, or expert peer review.

Books and long-form reading

“What does this difficult chapter mean without losing the original page?”

Follow characters, concepts, arguments, and recurring themes while the book remains visible. Use a quick orientation or slow down for a difficult paragraph.

Listen to Kindle books on your phone

Common inputs

EPUBPDFURLImage/OCRText

Illustrative reading approach

Overview before a chapter; Standard while reading; Deep for close reading, difficult prose, or conceptual nonfiction.

What CastReader can help surface

  • Chapter orientation
  • Character or concept context
  • Difficult-passage walkthrough
  • Connections to earlier ideas

Explanations may miss literary ambiguity or context outside the available passage. Keep the book as the primary source.

Reports and business documents

“What changed in this report, and which assumptions matter?”

Move from the executive summary into metrics, comparisons, risks, and dependencies without treating every paragraph as equally important.

Send reports and documents to CastReader

Common inputs

PDFDOCXURLImage/OCRText

Illustrative reading approach

Overview for a briefing; Standard for operating context; Deep for assumptions, risk language, and cross-section relationships.

What CastReader can help surface

  • Executive takeaways
  • Metric and period comparisons
  • Risks and dependencies
  • Questions for follow-up

Explanations are not financial advice and do not verify the accuracy, completeness, or future performance described in a report.

Study and exam preparation

“Teach me this section instead of only reading it aloud.”

Turn notes, textbook pages, slides, and readings into a guided review that identifies definitions, processes, relationships, and likely points of confusion.

Text to speech for students

Common inputs

PDFDOCXEPUBImage/OCRURLText

Illustrative reading approach

Overview for revision planning; Standard for learning; Deep for difficult mechanisms, derivations, and exam review.

What CastReader can help surface

  • Learning objectives
  • Concept breakdowns
  • Process and relationship maps
  • Review questions and weak spots

Use explanations as study support. Check formulas, quotations, citations, and course-specific requirements against the assigned material.

Manuals and technical documentation

“Explain this procedure step by step and point to the source.”

Follow prerequisites, terminology, sequences, warnings, and cross-references while preserving the procedure's original order and wording.

Read technical text in VS Code

Common inputs

URLPDFDOCXImage/OCRText

Illustrative reading approach

Standard for routine procedures; Deep for architecture, troubleshooting, safety notes, and interconnected steps.

What CastReader can help surface

  • Prerequisites and terminology
  • Step dependencies
  • Warnings and exceptions
  • Cross-referenced sections

For safety-critical work, follow the official manual and qualified instructions. An AI explanation must not override warnings or procedures.

Designed to support judgment, not replace it

The strongest use of Read & Explain is source-grounded comprehension: hear an explanation, see what it refers to, and verify important details in the original.

  • The original document remains the source of record.
  • AI explanations can be incomplete or mistaken and should be checked.
  • Legal, medical, financial, and safety-critical decisions need qualified review.
  • Output quality depends on extraction quality and the context available to CastReader.
  • Web files are parsed in the browser; the original file is not uploaded. AI reading sends needed text, including buffered paragraphs. Explain sends the paragraph chosen for that request.

Read & Explain — Questions

What's the difference between Read Aloud and Read & Explain?▾

Read speaks the original text. Explain gives a plain-language explanation with marks referring back to the source. Web Explain requires sign-in and an AI voice, and processes one paragraph in the document language.

What language does it explain in?▾

Web Explain follows the detected document language, with no output-language selector. Other clients may offer language settings; use only the options actually available there. The public AI voice catalog covers 28 languages, with 7 still in Beta.

Can it explain a page written in a language I don't read?▾

Web Explain follows the detected document language, with no output-language selector. Other clients may offer language settings; use only the options actually available there. The public AI voice catalog covers 28 languages, with 7 still in Beta.

Is Explain in My Language the same as translation?▾

No. Translation tries to reproduce the source wording in another language. Explain in My Language keeps the source visible and adds context, relationships, and plain-language meaning. Use reviewed translation when exact wording is the deliverable; use explanation when understanding is the obstacle.

How is this different from an AI summary tool?▾

A summary hands you a block of text. Read & Explain is a guided, spoken walkthrough: it talks you through the page while a pen circles and underlines the exact spots on the original, so you stay anchored to the source instead of trusting a detached summary.

Does it work on Kindle, WeRead, or PDFs?▾

Kindle, WeRead, and PDF use different extension, app, or document workflows. Availability depends on the client, access rights, and extractable content. The Web document tool needs a PDF text layer and cannot remove DRM or perform OCR.

Will the pen marks cover the text?▾

No. The pen uses light highlights, underlines, and circles that sit over the original without hiding it — just like marking up a printed page with a highlighter.

Is it free?▾

After signing in, Free includes 20 minutes of AI reading and 3 explanations per day. Device reading is available without an account, but device voices cannot run Explain. Personal voices require Pro and share 120 minutes per membership month across reading and explaining. See pricing for other Pro limits.

Which browsers are supported?▾

Use the download page for the current official browser-extension and mobile-app options. Client capabilities differ; a download listing does not mean every client supports every file format or Explain setting.

What are Overview, Standard, and Deep explanation?▾

Overview, Standard, and Deep describe different levels illustrated on this page. These demo tabs do not configure the reader. Web Explain currently uses Standard only; other clients depend on their available controls.

What types of content can CastReader explain?▾

Web accepts text-based PDF, DRM-free EPUB, DOCX, TXT, Markdown, and HTML. It does not OCR scanned pages. Webpage, image, and screenshot workflows depend on the extension or app and its actual support. Each Web Explain request uses one paragraph.

Try guided Read & Explain on your next difficult passage

After signing in, Free includes 3 explanations daily. Using personal voices requires Pro and shares 120 minutes per membership month across reading and explaining. See pricing for other limits.

Add to ChromeAdd to EdgeGet the iOS or Android app

More ways to listen

Listen to Kindle

Turn your Kindle library into audiobooks

Listen to AI chats

A listen button on every ChatGPT & Claude reply

Free TTS online

Paste text, pick a voice, listen instantly

PDF to audiobook

Read PDFs with a text layer; scanned pages need text extraction first

Reading voice library

Compare real voice samples for papers, books, and long documents