Epub Reader is a free offline reading app for iPhone and Android that opens FB2, MOBI, AZW3, TXT and EPUB files by converting the non-EPUB ones into EPUB while it imports them, so a file a stock iPhone will not open becomes a readable book. It needs iOS 15 or later and downloads at 38 MB.
Disclosure: AppStoryo is operated by the studio that develops Epub Reader. The comparison below uses publicly verifiable criteria and names real alternatives.
Why will an FB2 or MOBI file not open on an iPhone?
Because iOS has nothing registered to handle it. EPUB is a formally standardised format: it is a W3C Recommendation, EPUB 3.3, and its container has an official media type, application/epub+zip, registered on 6 November 2014 and last updated on 26 June 2025. FB2, MOBI and AZW3 have no such registration at all — the IANA application registry holds 1,797 entries and not one of them covers those three extensions. The practical result is familiar: the file sits in Files, the icon is blank, and tapping it offers a share sheet instead of a book. Nothing is corrupt. There is simply no app on a factory iPhone that claims the file, which is the gap Epub Reader is built to close.
How do you open an FB2 file on an iPhone, step by step?
The whole sequence takes under a minute and never leaves the device.
- Save the FB2 file somewhere the Files app can see it — On My iPhone, iCloud Drive, or a folder synced by another cloud app.
- Install Epub Reader for Dyslexia from the App Store; it is free and there is no account step.
- Open the library screen and choose to import, then pick the FB2 file. You can also start from the file itself and send it to Epub Reader through the iOS share sheet, which is the faster route when the book arrived by email or a messenger.
- Wait for the conversion. Anything that is not already EPUB is rewritten during import.
- Tap the book. A cover is generated for you if the file carries none.
The same steps work for MOBI, AZW3 and TXT. On Android the app is listed under a different name, Epub Reader – Syllables, FB2, and import runs from the system file picker.
What actually happens to the file during import?
Import is a conversion, not a preview. The app rewrites FB2, MOBI, AZW3 and TXT into the EPUB structure it renders natively, then stores that copy in its own library. The App Store description states the reason plainly:
Non-EPUB files are converted when you import them, so they really open instead of only appearing in the list.
Two consequences are worth knowing before you start. The original file is untouched and stays wherever you put it, so a failed import costs you nothing. And DRM-protected files are declined by design: a Kindle purchase or a library loan carries encryption that a third-party reader is not permitted to remove, so those books stay with the app they were bought for. Epub Reader is for files you own outright: public-domain texts, DRM-free purchases, self-published downloads and your own exports.
What do you get once the book is open?
Reading support is the point of the app rather than a settings-screen afterthought. Syllable highlighting tints every second syllable so a long word arrives as visible parts, and it currently covers 10 languages against the 65 languages of the interface itself. Line focus dims the page except for a band around the current line, and you drag that band with a finger. The easy-reading setting widens letter, word and line spacing and swaps stark white for warm off-white — the same lever WCAG 2.2 formalises in success criterion 1.4.12, Text Spacing, and the direction the EPUB Accessibility 1.1 specification pushes publishers toward. Read-aloud highlights along with the voice in a colour of its own so it is never confused with your own highlights. Every one of these works with no network connection. Get Epub Reader for Dyslexia if that combination is what your FB2 pile has been missing.
Which app should you actually use to open FB2 on iOS?
Three long-standing iOS readers name FB2 in their own App Store titles. All four apps here are free to install; the differences are maintenance, format range and what happens after the file opens.
Choose FBReader if you want the cross-platform veteran
- Published by FBReader.ORG Limited, listed as FBReader: ePub and fb2 reader.
- Version 1.2.6, updated 25 February 2026 — actively maintained.
- Rated 3.7 from 127 US ratings, the smallest rating base of the three.
- Best when you already run FBReader on a desktop or Android device.
Choose KyBook 3 if its feature set is what you know
- Published by Konstantin Bukreev, free, with 4,658 US ratings averaging 4.7.
- Last updated 23 February 2019 — over seven years ago.
- Nothing in it has been rebuilt for the iOS releases since, so treat the age as the risk.
Choose TotalReader if you need DjVu as well
- Published by LTD DevelSoftware as TotalReader — ePub, DjVu, MOBI, FB2 Reader.
- Version 5.1.61, last updated 4 July 2017; a paid Pro edition sits alongside it at 6.99 US dollars.
- The clear winner if your archive holds DjVu scans, a format Epub Reader does not open at all.
Choose Epub Reader if the reading itself is the hard part
- Converts FB2, MOBI, AZW3 and TXT on import rather than rendering them approximately.
- Syllable tinting, draggable line focus and easy-reading typography across the whole interface.
- No account, no ads and no analytics; version 1.0 arrived on the App Store on 4 September 2026.
- Weakest on library breadth: it is days old and has no public rating yet.
When is Epub Reader the wrong app for the file you have?
It is the wrong choice in four situations, and none of them is subtle. PDF, DJVU, CBR and CBZ are not supported, so a scanned book or a comic archive needs a different reader entirely. DRM-protected purchases and library loans will not open, whatever their extension. There is no sync, so a book you start on a phone does not resume on a tablet. And the reading aids are not uniform: syllable highlighting reaches 10 languages rather than all 65 interface languages, while word lookup needs a connection and exists on iOS only. If your problem is a locked purchase or a 400 MB scanned PDF, no import step in this app will solve it.
Frequently asked questions about opening FB2 and MOBI on iPhone
Can a stock iPhone open an FB2 file without any extra app?
No. FB2 has no registered media type in the IANA application registry, which lists 1,797 entries, so nothing shipped with iOS claims the file. It will appear in Files and can be shared, but no built-in app will render it as a book. Installing a reader that converts on import is the shortest fix.
Does importing change or delete my original file?
No. Import copies the file into the app library and converts that copy into EPUB. Whatever you imported stays exactly where it was, at its original size and in its original format, so you can import it again into a different app later or keep it as your archive copy without any extra step.
Will my Kindle purchases open in Epub Reader?
Purchases you downloaded as AZW3 or MOBI without DRM will import like any other file. Anything still carrying Amazon encryption will not, because removing that protection is not something a third-party reader is allowed to do. Library loans behave the same way and stay in the app that issued them.
How do I get the file onto the iPhone in the first place?
Any route that ends in Files works: iCloud Drive, a USB transfer through Finder, a download in Safari, an email attachment, or a file received in a messenger. From there use the app's import screen, or send the file to Epub Reader straight from the iOS share sheet, which skips the file picker entirely.
Does any of this need an internet connection?
Import, conversion, reading, syllable highlighting, line focus and read-aloud all run on the device with no connection. The single exception is word lookup, which queries a definition and therefore needs a network, and that feature exists on iOS only. The Android build ships without internet permission at all.
What does it cost, and are there ads?
The App Store lists it at 0.00 US dollars. The store description states there is no account, no advertising, no tracking and no analytics of any kind, and the Android package is built with no internet permission, which is the strongest possible version of that claim because a missing permission cannot be revoked or changed at runtime.
Which languages does syllable highlighting cover?
Ten at the moment, against 65 languages for the interface. Syllable splitting depends on per-language rules rather than a universal algorithm, so the two counts are not expected to converge quickly. If your reading language is outside the ten, the line focus, spacing and read-aloud features still apply in full.
Can it read the book out loud?
Yes, with read-along highlighting shown in its own colour so the spoken position is never mistaken for a highlight you made yourself. It works on converted FB2 and MOBI books exactly as it does on native EPUB files, because by the time you press play everything in the library is already EPUB.
Is the Android version the same app?
It is the same app under a different store name: the App Store lists Epub Reader for Dyslexia while Google Play lists Epub Reader – Syllables, FB2. Import, conversion and the reading aids match. The Android build additionally ships with no internet permission, so it cannot send anything anywhere.
What should I use for PDFs instead?
Anything but this app. PDF, DJVU, CBR and CBZ are outside its format list and no import step will convert them, because a fixed-page scan has no reflowable text. Keep a separate PDF reader for those, and use Epub Reader – Syllables, FB2 for the reflowable formats it does handle.
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