The short answer
calibre's content server publishes your library as an OPDS catalog. Start the server on your computer, take its address and add /opds at the end (for example http://192.168.1.5:8080/opds), then add that URL as a catalog in VocaRead on an iPhone connected to the same Wi-Fi. You can then browse, search and download books into your library and listen to them offline.
What OPDS is
OPDS (Open Publication Distribution System) is an open, feed-based format for describing a collection of ebooks so that reading apps can browse it, search it and download from it. It isn't a file format and it isn't a sync service: think of it as a library catalog that apps can read. calibre, Kavita and Komga all expose one, which means a single reading app can talk to any of them without a dedicated plugin.
For a calibre user, the appeal is simple: your library stays organized where it already is, and your iPhone picks books from it over the network instead of you emailing files to yourself or copying them by cable.
Step 1: Start calibre's content server
- In calibre, click the Connect/share button and choose Start Content server.
- Open the same menu again. While the server runs, it shows a Stop Content server entry with the computer's address and port in brackets, such as [192.168.1.5, port 8080]. Note both numbers.
- Optional: in Preferences › Sharing over the net, tick Run server automatically when calibre starts so you don't have to start it by hand each time. The port is set on the same screen; 8080 is the default.
The server only answers while calibre is running and the computer is awake. Books you've already downloaded to your iPhone don't depend on it.
Step 2: Build and test the OPDS address
The OPDS address is the server address followed by /opds: http://, the IP address, a colon, the port, then /opds. With the example above, that's http://192.168.1.5:8080/opds.
Before touching VocaRead, open http://192.168.1.5:8080 (without /opds) in Safari on your iPhone. If calibre's web interface appears, the network side works and any later problem is in the app settings. If Safari can't connect, fix that first; the troubleshooting table below covers the usual causes.
One thing to know: on most home networks, your computer's local IP address is handed out by the router and can change after a restart. If the catalog suddenly stops working one day, check the address again. Reserving a fixed address for the computer in your router's settings avoids the problem for good.
Step 3: check compatibility
VocaRead does not support the Digest authentication used by calibre. This guide covers only a local catalogue without authentication on a trusted network. If your library is password protected, keep its protection and import DRM-free files into VocaRead instead.
Kavita, Komga and other OPDS servers
Kavita and Komga are self-hosted library servers that also expose an OPDS catalog. The principle is the same as with calibre, but the details depend on the server and its version, so look in your server's settings or documentation for its OPDS address. Two things to watch for:
- Authentication varies. Some servers ask for a username and password, some use a token, and some put a personal key directly in the OPDS address. Pick the matching option when you add the catalog.
- Comics have nothing to read aloud. These servers are often used for comics and manga as well as ebooks. VocaRead downloads the text formats it can import (EPUB, PDF, MOBI, AZW and AZW3); image-only comics aren't something a voice can narrate.
Step 4: Add the catalog in VocaRead
- Open the import screen and choose OPDS Catalogs, then Add a catalog.
- Give it a name you'll recognize, such as "calibre at home", and paste the Catalog URL ending in /opds.
- For this local catalog, leave authentication set to None.
- Save. The first time, iOS asks whether VocaRead may find and connect to devices on your local network. Allow it, or the app can't reach your computer.
You can now browse the sections your server offers (for calibre, views such as authors and series), search the catalog, and download a book straight into your library. From there it behaves like any imported book: pick a voice, set the speed, and listen without a connection.
Which format to download
When a book exists in several formats in calibre, prefer EPUB. It keeps the chapter structure, which gives you a clean chapter list; our EPUB support page shows what that looks like. MOBI and AZW3 files work if they're DRM-free (see listening to Kindle files), and calibre's Convert books can make an EPUB from them if you prefer. PDF works too, but layout-heavy PDFs read less smoothly than reflowable formats. EPUB imports are limited to 35 MB, which mainly matters for heavily illustrated editions.
Troubleshooting
| Symptom | Likely cause | What to do |
|---|---|---|
| Safari can't open the server address | Different networks, or the computer is asleep | Put both on the same Wi-Fi (not a guest network, not cellular, no VPN on the phone) and wake the computer |
| Safari can't connect, both on the same Wi-Fi | Firewall on the computer | Allow calibre, or its port, through the firewall and any security software |
| Safari works, VocaRead doesn't | Local network access denied | Turn on Local Network for VocaRead in Settings › Privacy & Security › Local Network |
| Worked last week, not today | The computer's IP address changed | Check the address in calibre's menu, update the catalog, reserve the address in your router |
| A book downloads but won't import | DRM protection, or an EPUB over 35 MB | Use a DRM-free copy; VocaRead doesn't remove DRM |
About http and https: on your home network, a plain http:// address is normal for calibre and usually all you need. Exposing an unencrypted server to the internet so you can reach it from outside is a bad idea. If you want access away from home, the safer routes are a VPN into your home network or a reverse proxy with https in front of the server.
A note on DRM: calibre stores whatever files you give it. Books bought from stores that lock them with DRM (most Kindle and Apple Books purchases) remain locked inside calibre, and VocaRead can't play them. Files you bought DRM-free, or public-domain books, work normally. For the latter, VocaRead also has the Project Gutenberg catalogue built in, no server required.
Frequently asked questions
Does calibre need to stay running while I listen?
No. calibre only needs to run while you browse and download. Once a book is in VocaRead's library, it plays offline like any other imported book.
Can I reach my calibre library when I'm away from home?
Not out of the box: the setup above is meant for your local network. A VPN into your home network makes the same local address work remotely. Avoid opening a plain http server to the internet.
Does my listening progress go back to calibre?
OPDS is for browsing and downloading. Your progress, bookmarks and notes live in VocaRead and sync between your iPhone and iPad through your personal iCloud if you turn sync on.
Can I use Kavita or Komga instead of calibre?
Yes. Both expose an OPDS catalog. Find the OPDS address and the authentication method in your server's settings, then add it in VocaRead the same way.
Why can't I download some titles from the catalog?
The server only offers them in a format VocaRead doesn't import, such as a comic archive. Convert it in calibre if it's a text ebook, or skip it if it's image-only.
If you already keep your books in calibre, VocaRead is free to download and connect to it. Every book includes 90 minutes of free listening, and Premium is a one-time purchase that unlocks unlimited listening, with no subscription.