The e-book format CHM (Compiled HTML Help) was developed by Microsoft back in the late 90s and still remains popular for distributing technical documentation and reference books. However, if you try to open such a file on a smartphone using standard means, the system simply will not understand what is required of it. This is due to the fact that Android initially does not support this proprietary data structure.
Users often encounter a situation where they have downloaded the book they need, but when they click on the file they see only an error message or a list of apps that cannot read the content. Don’t panic, the situation can be solved with the help of specialized software. In this article, we will look in detail at which application to choose, how to customize the display, and what to do if the text is not displayed correctly.
Choosing the right tool depends on your goals: do you just need to read the text, or do you need full navigation through the table of contents with bookmarks saved. Modern solutions allow you to comfortably work with archives .chm right on the touch screen without the need to convert them. Below we will present a detailed analysis of the available methods and utilities.
Specialized applications for reading CHM
The most effective solution is to install a separate application tailored specifically for this format. Unlike universal readers, such apps can correctly index the internal structure of a file, providing quick navigation through links and sections. One of the most popular utilities is ReadErawhich is completely free and does not contain annoying advertising.
This application automatically scans the device memory and finds all available documents. After installation, you do not need to manually search for the file through Explorer - it will immediately appear in the library. The interface ReadEra is intuitive: the table of contents is displayed on the left, and the main text on the right with the ability to change the font and theme.
Another powerful tool is considered CHM Viewer from various developers. Such apps often offer additional functions, such as text search or read-aloud mode. It is important to note that some old applications may not work correctly on new versions Android 13 or Android 14 due to changes in the file access policy.
Before installing the application, check its compatibility with your version of Android in the Google Play store description to avoid conflicts and crashes.
When choosing software, it is worth paying attention to the presence of a night mode, since reading technical literature often lasts until late in the evening. Your eyes will thank you for the opportunity to switch to a dark theme with a yellowish tint, which reduces eye strain.
Universal readers with support for formats
If you don’t want to clutter up your phone’s memory with unnecessary icons, you can use multifunctional processors. apps like Moon+ Reader or Lithium support dozens of formats, including EPUB, FB2 and, of course, CHM. This is convenient if your library consists of books of different types.
The main advantage of such solutions is a single design setting for all books. You adjust indents, line spacing, and font once, and these settings apply to all documents. However, it is worth considering that universal readers are sometimes slower to open complex CHM archives compared to specialized utilities.
Some users prefer Google Play Booksuploading their files there via the cloud. This allows you to synchronize your reading progress between your phone, tablet and computer. But to work with .chm in the Google ecosystem, sometimes a preliminary file conversion is required, since native support may be limited.
- 📚 Moon+ Reader is a powerful all-in-one tool with flexible settings for gestures and themes.
- 🔍 Lithium is a minimalist reader with Material Design and fast work.
- ☁️ Google Play Books —a cloud solution for synchronizing progress on all devices.
When using third-party readers, pay attention to the permissions they request. To work correctly, they need access to storage, but requiring access to contacts or a microphone to read books is absolutely unnecessary.
Encoding problems and their solutions
One of the most A common problem when opening CHM files on Android is incorrect display of text. Instead of letters, you may see a set of incomprehensible symbols or “krakozyabry”. This occurs due to a mismatch between the encoding in which the file is saved (often Windows-1251) and the encoding that the application is trying to apply (usually UTF-8).
In most advanced readers, such as ReadEra, this problem is solved automatically or through the settings. You need to go to the book menu, find the "Encoding" item and manually select Windows-1251 or KOI8-R. After this, the text will immediately become readable.
⚠️ Attention: If changing the encoding in the application settings did not help, the file itself may be damaged or saved in an exotic encoding that mobile applications do not support. In this case, only conversion to a PC will help.
It is also worth considering that some files contain built-in fonts that may conflict with the system fonts of your smartphone. If the text looks blurry or too small, try disabling the use of built-in fonts in the reader settings.
Converting CHM to other formats
If no application can open the file, conversion remains the most reliable way. Converting .chm to PDF or EPUB guarantees that the book will open on any device without problems with encoding and structure. This method is especially relevant for documents with complex formatting and tables.
For conversion, you can use online services such as Convertio or Online-Convert. You don't need to install apps on your computer: just upload the file to the site, select the target format and download the result. The process takes only a few minutes depending on the size of the archive.
An alternative option is to use desktop software like Calibre. This is a free book library management app that allows you to batch convert hundreds of files at once. It gives you more control over the quality of the final document, allowing you to edit metadata and table of contents.
Why can conversion to PDF spoil pictures?
When converting CHM to PDF, the quality of raster images is sometimes lost or the layout of tables is lost, since the original format uses an HTML engine, and PDF uses a fixed layout. It is better to try converting to EPUB to maintain adaptability.
After conversion, the file will become heavier, since the format EPUB or PDF is less efficient in compression than the original .chm. Take this into account if the memory of your smartphone is limited.
Navigation and additional functions
The main advantage of the format CHM over plain text is the presence of hyperlinks and an interactive table of contents. A good reading app should support quick navigation through these elements. In high-quality readers, when you click on a link in the text, you instantly jump to the desired section without reloading the entire book.
The bookmark function is also critically important for technical literature. You can mark important pages and return to them later. Some applications allow you to export a list of bookmarks, which is convenient when preparing reports or notes.
| Application | Table of contents support | Text search | Night mode |
|---|---|---|---|
| ReadEra | Yes | Yes | Yes |
| Moon+ Reader | Yes | Yes | Yes (flexible) |
| CHM Viewer | Partly | Yes | No |
| Google Books | Yes (after conversion) | Yes | Yes |
Pay attention to the "Continuous scrolling" function. In some books, the text is divided into separate HTML pages, and while reading you have to constantly click “Next”. Modern applications are able to glue these pages together into a single canvas, making reading smoother.
For technical documentation with a lot of links and transitions, it is critical to choose applications that fully support internal CHM navigation, otherwise reading will turn into torture.
Security and file sources
Format CHM may contain executable scripts, which theoretically makes it potentially dangerous, although on Android the risk of infection is minimal due to the sandbox of the system. However, you should download files only from trusted sources, such as official websites of equipment manufacturers or well-known libraries.
Avoid sites that require sending an SMS to download a book or install dubious plugins. Adware is often distributed under the guise of books. Before opening a downloaded file, it would be a good idea to scan it with the built-in antivirus or service VirusTotal.
⚠️ Attention: Never open CHM files received from unknown senders in instant messengers, especially if they are disguised as documents or invoices. This is a common phishing method.
If you use a file manager to open books, make sure it is reputable. Some "cleaners" and phone boosters can intercept files and replace them with advertising links.
Frequently asked questions (FAQ)
Why does the CHM file not open even after installing the application?
The file may be damaged during downloading or has a non-standard structure. Try opening it on your computer to check its integrity. Also check if the application has permission to access the phone's memory in the system settings.
Is it possible to edit CHM files on Android?
No, mobile applications are read-only. The CHM format is compiled, and changing it requires special software on a PC, such as HTML Help Workshop.
How to extract pictures from a CHM book?
Some advanced file managers allow you to open CHM as an archive. Otherwise, the easiest way is to take screenshots of the necessary pages or convert the book into a format from which it is easier to extract media content.
Will searching the book work if the text is displayed as hieroglyphs?
No, the search will not work correctly until the encoding is corrected. First, make the text readable through the app settings, and only then use the search function.