# Calibre

Application: Kovid Goyal

Also called calibre ebook, calibre library

Kovid Goyal, Productivity

An ebook library and converter. The process is calibre.exe. It is not the Kindle app.

## What you need to know

Calibre is a library and converter. Kindle is Amazon's store app.

calibre.exe organizes and converts ebooks you already have. The Kindle for PC app is a different vendor and will not replace this converter.

- **What is it?**: Ebook library

  **Still current?**: Yes, see Current status

  **Official download?**: Use the vendor link in this article

Feex says

If conversion is slow, I would watch calibre-parallel.exe, not the Kindle app. Amazon's client does not do this job.

## What is Calibre?

Calibre is an open-source ebook manager. calibre.exe is the library. Conversions can spawn calibre-parallel.exe. The Kindle app will not convert your EPUBs.

## If you have never used it

If you need to convert an EPUB, organize a personal ebook library, or talk to a reader over USB, this is Calibre, not the Kindle app. Download it from calibre-ebook.com/download_windows. The Kindle app from Amazon reads Amazon books. Calibre is Kovid Goyal's library and converter. It is not a store.

## What is it used for?

**Library and metadata**

Tag and fetch covers for books you already own. Amazon's Kindle app is a store shelf, not this catalog.

**Format conversion**

EPUB, AZW3, PDF, and others. That conversion is why people install Calibre next to a Kindle.

**Send to device**

USB or email-to-device workflows Calibre documents. That is not Amazon's cloud send from the Kindle app alone.

## Who is it for?

- People who buy EPUBs outside one store
- Users who convert before a trip
- Anyone who should not open the Kindle app expecting a converter

## Current status

Actively developed. 64-bit Windows builds are the current recommendation on the download page.

## How old is it?

Kovid Goyal started Calibre in 2006. It is older than many store apps and still GPL. The Kindle for PC app is Amazon's store client. They are not the same library.

## Versions

Major channels first. Exact build numbers are not all verified here.

64-bit Windows

Portable

## System requirements

Values follow the publisher's public guidance. Workload still changes the real need.

### Minimum

| Operating system | A current supported Windows 10 or Windows 11 release, per the vendor |
| ---------------- | -------------------------------------------------------------------- |
| RAM              | Enough for Windows plus this app. Heavy projects want more.          |

## Resource profile

- **CPU demand**: Follows what you open inside the app

  **RAM demand**: Follows documents, tabs, or libraries

## Installed processes

These executables belong to this product when it is installed.

| calibre.exe          | Library window         |
| -------------------- | ---------------------- |
| calibre-parallel.exe | Worker for conversions |

## Startup components

Calibre starts when you open the library. The content server is an optional setting, not a Windows service by default.

## File locations

| Typical install | C:\Program Files\Calibre2\calibre.exe |
| --------------- | ------------------------------------- |

## File formats

EPUB, AZW3, MOBI, PDF, CBZ

## Common problems

### Conversion sits on CPU

Large PDFs to EPUB are heavy. That is expected worker time, not a virus named calibre-parallel.exe.

### People look for a Kindle store inside Calibre

Calibre is not Amazon. Buy or sideload the file, then add it here.

## Getting unstuck

### Install the 64-bit build from calibre-ebook.com/download_windows

A "Calibre ebook crack" search ad is the wrong file.

### Do not delete the Calibre library folder while the app is open

The library is your books plus a metadata database. That is not the Kindle documents folder.

### If a Kindle book is DRM-locked, Calibre cannot legally strip that

Conversion of files you may convert is the supported story. A "DRM plugin" from a forum is the wrong path.

## Alternatives

The Kindle app, Apple Books, and Sumatra PDF overlap for reading. None of them is this converter library.

## Official help and downloads

Start with the vendor. Random exe sites are not a support channel.

| Download      | [calibre-ebook.com/download_windows ](https://calibre-ebook.com/download_windows)Official installer or vendor page |
| ------------- | ------------------------------------------------------------------------------------------------------------------ |
| Help          | [manual.calibre-ebook.com/ ](https://manual.calibre-ebook.com/)Vendor support                                      |
| Official site | [calibre-ebook.com/download_windows ](https://calibre-ebook.com/download_windows)Start here, not a random exe host |

## Related hardware

Conversions want CPU and disk. An SSD helps large PDF jobs.

## Technical details

Technical details

Vendor version numbers change. This article does not pin a build.

## Related

These entities connect to this article. Type is shown on every link.

[How to read Task Manager: Guide](https://feex.it/wiki/software/system/how-to-read-task-manager)

## Sources and verification

Reviewed by Feex editorial. Last verified August 2026 Status: Feex Reviewed. [How we research](https://feex.it/wiki/research).

- [Calibre official site ](https://calibre-ebook.com/download_windows)· Vendor product page
- [Calibre help ](https://manual.calibre-ebook.com/)· Vendor support
- [Calibre about ](https://calibre-ebook.com/about)· What the project is
- [Foxhole process map ](https://foxhole.feex.it/)· First-party samples on Windows PCs. Not a lab benchmark.

## Was this article useful?

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Quick facts

The short identity of this page. Specs, sources, and the full story stay in the article.

- **Developer**: Kovid Goyal

  **Category**: Ebook library

  **Process**: calibre.exe

  **License**: GPL open source

  **First released**: 2006

  **Official site**: [calibre-ebook.com](https://calibre-ebook.com/download_windows)

  **Mapped by Feex**: Seen on Windows PCs in Foxhole

Feex Reviewed: Last verified August 2026

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Source: [Canonical Feex Wiki page](https://feex.it/wiki/software/calibre/)

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