If you own a Kobo e-reader, you may have come across the term OPDS while looking for ways to load books onto your device. Maybe someone in a forum mentioned an OPDS catalog, or you saw the option in KOReader’s menu and wondered what it does.
OPDS is one of the most useful protocols in the ebook world, and one of the least well-known. Here’s what it is, why it matters, and how to use it on Kobo, iPhone, iPad, and Mac.
What Is OPDS?
OPDS stands for Open Publication Distribution System. It’s an open standard that lets reading apps browse and download ebooks from a catalog, similar to how RSS lets apps subscribe to news feeds. Instead of visiting a website, finding a book, downloading a file, and transferring it to your device, OPDS puts the catalog inside your reading app. You search, browse, and download in one place.
The protocol was designed by ebook developers and publishers who wanted a universal way to distribute books. Any OPDS-compatible app can connect to any OPDS-compatible server. There’s no vendor lock-in, no proprietary format, no account required for public catalogs. It’s the open web applied to ebooks.
OPDS catalogs serve two types of content: public catalogs with free books (Standard Ebooks, Internet Archive) and private catalogs for personal libraries (like a Calibre server on your home network). Both work the same way from the reader’s perspective.
Why Kobo Users Care About OPDS
Kobo e-readers are popular with readers who prefer open formats over Amazon’s locked ecosystem. Kobo devices read EPUB natively, support library borrowing through OverDrive, and generally play well with the broader ebook world.
The catch: Kobo’s stock firmware does not include an OPDS catalog browser. You can sideload books manually over USB or buy from the Kobo store, but there’s no built-in way to connect to an OPDS catalog.
That’s where KOReader comes in. KOReader is a free, open-source reading app that can be installed alongside Kobo’s stock firmware. Once installed, it adds a full OPDS catalog browser to your Kobo. You can connect to Standard Ebooks, Internet Archive, your own Calibre server, or any other OPDS feed and download books directly over Wi-Fi.
If you have a Kobo running KOReader and a Mac running BookShelves, you can even browse your BookShelves library from your Kobo using the built-in OPDS server. For syncing books and reading progress between KOReader and BookShelves, see the Calibre wireless sync guide.
OPDS Catalogs Worth Knowing
Not all OPDS catalogs are equal. Here are the ones that consistently provide high-quality, free, legal ebooks.
Standard Ebooks produces beautifully formatted public domain classics. Every book is hand-proofed, typographically polished, and published as a modern EPUB3 with proper metadata and cover art. The catalog is smaller (around 900 titles), but the quality is dramatically higher than other sources. OPDS feed: https://standardebooks.org/feeds/opds
Internet Archive has over 20 million books in its Open Library. The OPDS feed provides access to a large portion of that collection, including public domain works and controlled digital lending titles. The sheer scale makes it the largest freely accessible ebook catalog in the world.
Calibre Content Server is not a public catalog but a personal one. If you manage your ebook library with Calibre on a desktop computer, Calibre’s built-in content server includes an OPDS endpoint. Any OPDS-compatible app on your network can browse and download from your personal library. This is the most common way people set up private OPDS catalogs at home.
Aozora Bunko is a volunteer-run digital library of Japanese literature. BookShelves includes Aozora Bunko as a built-in catalog with professionally typeset EPUBs and cover art.
BNE (Biblioteca Nacional de España) provides digitized works from Spain’s national library, including classic Spanish literature. Also available as a built-in catalog in BookShelves.
Browse OPDS catalogs on iPhone, iPad, and Mac
BookShelves connects to any OPDS catalog. Standard Ebooks, Internet Archive, and more are built in.
Using OPDS on iPhone, iPad, and Mac
If you read on Apple devices, you don’t need a Kobo or KOReader to use OPDS. BookShelves has a built-in OPDS catalog browser that works on iPhone, iPad, and Mac.
Built-in catalogs are ready to browse immediately. Open BookShelves, go to the Discover section, and you’ll find Standard Ebooks, Internet Archive, and more already configured. Tap any catalog to browse by category, search by title or author, and download books with a single tap.
Custom OPDS catalogs can be added manually. If you run a Calibre content server at home, or you have the URL for any other OPDS feed, you can add it in BookShelves and browse it alongside the built-in catalogs. This is useful for personal libraries, institutional catalogs, or smaller independent OPDS servers.
Downloaded books go straight into your BookShelves library with full metadata, covers, and iCloud sync across all your Apple devices. There’s no extra step to import or organize them.
Using OPDS on a Kobo
On a stock Kobo, your options are limited to the Kobo store and manual USB transfers. To use OPDS catalogs on a Kobo, you need KOReader.
Installing KOReader on Kobo is straightforward and does not remove the stock Kobo firmware. You can switch between KOReader and the stock Kobo software at any time. The KOReader wiki has step-by-step instructions for every Kobo model.
Adding OPDS catalogs in KOReader:
- Open KOReader on your Kobo
- Tap the magnifying glass icon in the top toolbar
- Select OPDS catalog
- Tap the + icon to add a new catalog
- Enter a name and the catalog URL (for example,
https://standardebooks.org/feeds/opds) - Browse and download books over Wi-Fi
KOReader comes with several OPDS catalogs pre-configured, so you may find Standard Ebooks and others already available without adding them manually.
OPDS vs. Other Ways to Get Books
OPDS vs. USB transfer: OPDS downloads books over Wi-Fi. No cables, no dragging files, no mounting drives. Much faster for grabbing a single book. USB is still better for transferring hundreds of books at once.
OPDS vs. store purchases: OPDS catalogs are typically free or serve your personal library. They don’t replace buying books from a store, but they’re the best way to access public domain literature and personal collections without friction.
OPDS vs. browser downloads: You could visit standardebooks.org in a browser, download an EPUB, and transfer it to your device. OPDS does the same thing from inside your reading app, in fewer steps. The convenience adds up when you’re browsing and downloading regularly.
OPDS vs. Calibre wireless: OPDS is read-only and one direction: you browse a catalog and download books. Calibre’s wireless device protocol is two-way, designed for syncing books and reading progress between devices. If you use both BookShelves and KOReader, you might want both protocols running.
The OPDS Ecosystem
OPDS is maintained as an open specification. The current versions are OPDS 1.2 (based on Atom/XML) and OPDS 2.0 (based on JSON). Most servers and clients support 1.2, with 2.0 adoption growing. BookShelves supports both versions.
The protocol has been adopted by libraries, publishers, and independent developers worldwide. It’s not flashy, it doesn’t get much press, but it quietly powers a lot of the open ebook infrastructure that readers depend on. If you care about reading books without being locked into a single store or ecosystem, OPDS is one of the tools that makes that possible.
Related Guides
- KOReader OPDS Setup: Send Books to Kindle and Kobo over Wi-Fi - Browse your BookShelves library from KOReader
- Sync Books with KOReader via Calibre Wireless - Push books and sync reading progress
- Where to Buy DRM-Free Ebooks - Stores that sell ebooks without copy protection
- 30 Best Free Classic Books - Public domain classics worth reading