Smartphone owners are often faced with the need to read technical documentation, reference books or old e-books saved in a specific format. Files with the extension .chm (Compiled HTML Help) are a standard for Microsoft help systems and are still widely distributed on the Internet. However, the operating system Android initially does not have built-in tools for correctly displaying such content.
An attempt to open such a file with a standard document viewer often results in an error or displaying an incomprehensible set of characters. This is due to the fact that it CHM is a compressed archive of HTML pages that requires a special decoder. Without installing third-party software, it is almost impossible to access the information inside the container.
Fortunately, the ecosystem Google Play offers many solutions to this problem. In this article we will analyze in detail which applications cope with the task best, how to avoid problems with Cyrillic encoding and what settings may be required for comfortable reading of technical literature on a mobile device.
Reasons for the lack of native support for the format
Historically, the format CHM was developed by the corporation Microsoft exclusively for your operating system Windows. It was created as a replacement for outdated help files .hlp and used the Internet Explorer engine to render the content. The kernel-based architecture never included components for working with this proprietary format. Androidkernel based Linux, never included components to work with this proprietary format.
The main difficulty lies not only in the file structure, but also in the methods of data compression. Inside CHM container there may be hundreds of HTML files, images and scripts packed with a specific algorithm. Standard archivers on a phone can see the folder structure, but are not able to correctly interpret the contents without a specialized plugin or a separate reader application.
⚠️ Attention: Do not try to simply rename the file extension from .chm to .zip or .rar. Although the internal structure does resemble an archive, directly extracting files often results in lost navigation and broken links between pages.
There is also a security issue. In the past, the format CHM has been repeatedly used by attackers to distribute malicious code through vulnerabilities in scripts. For this reason, many mobile browsers and file managers block the direct launch of such files, requiring the installation of proven software from official sources.
Best applications for reading CHM on smartphones
Today, several dozen apps are available in the store, positioning themselves as universal readers. However, not all of them cope equally well with displaying complex layouts and tables of contents. We analyzed popular solutions and identified market leaders who guarantee stable operation. Google Play There are several dozen apps available that position themselves as universal readers. However, not all of them cope equally well with displaying complex layouts and tables of contents. We analyzed popular solutions and identified market leaders who guarantee stable operation.
One of the most reliable options is the application CHM Reader. It features a minimalistic interface and high speed even on older devices. The app automatically recognizes text encoding, which is critically important for Russian users, since many technical manuals were created a long time ago and use different character encoding standards.
Another powerful tool is ReadEra. This is a universal combine that supports not only CHMbut also PDF, EPUB, FB2 and other formats. Its main advantage is the absence of advertising in the free version and the ability to remember the place where you stopped. For those who read a lot of technical literature, this is an indispensable feature.
It is also worth mentioning the application CHM File Viewer from the developer Peaksel. It offers advanced search functions within the text within the book and convenient navigation through the table of contents. The interface is made in the style Material Design, which provides a pleasant visual experience and full adaptation to touch controls.
- 📚 CHM Reader - a lightweight application with a focus on speed and ease of use.
- 📖 ReadEra - a universal reader without unnecessary water, supporting synchronization of progress.
- 🔍 CHM File Viewer - a powerful tool with advanced search and a beautiful interface.
- 🛠️ OlReader - supports many formats and allows you to customize fonts for yourself.
Step-by-step guide for installation and configuration
The installation process of software for reading CHM files is maximally simplified in modern versions Android. However, for the application to function correctly, it may require certain permissions to access the data storage. Below is a sequence of actions that will help you start reading in a matter of minutes.
First, you need to go to the application store Google Play and enter the name of the selected reader in the search bar, for example, CHM Reader. After selecting the application, click the "Install" button. Wait for the download to complete and the package to be automatically installed on your device.
☑️ Installing the reading app
When you first launch the app, it will ask for permission to access files on your device. This is necessary so that the reader can scan the phone's memory and find files with the extension .chm. Without granting this right, you will see an empty list of books. Confirm the request in the system dialog.
If the file is in the downloads folder or received via messenger, you can open it directly through the file manager. Click on the file CHM, and the system will prompt you to select an application to open. Select the installed reader and check the box “Always use this application” so that in the future files will be opened automatically.
⚠️ Attention: In versions of Android 11 and higher, access to the file system has become more restrictive. If the application does not see your books, you may have to manually specify the path to the folder through the built-in explorer of the reader itself.
For quick access to your favorite books, add an application shortcut to the home screen and use the “Last Open” widget, if it is supported by the selected reader.
Solving problems with encoding and text display
One One of the most common problems when reading old reference books on Android is the incorrect display of the Cyrillic alphabet. Instead of Russian letters, the user sees a set of incomprehensible symbols or “krakozyabr”. This is due to the fact that the file was saved in an outdated encoding, for example Windows-1251 or KOI8-R, and the application by default tries to open it in UTF-8.
Most modern readers, such as ReadEra or CHM Readerhave an auto-detection function encodings However, the algorithm does not always work perfectly. If you encounter a problem, go to the application settings and find the section responsible for text encoding. Manually switch the value to Windows-1251 or CP1251.
In some cases, the problem may lie not in the encoding, but in damage to the file itself. If switching options doesn't help, try opening the same file on your computer. If the text is displayed incorrectly there too, it means that the file was downloaded with an error or was initially saved incorrectly. In such a situation, only searching for an alternative source will help.
What to do if the pictures do not load?
Inside the CHM file, the images may be damaged or the links to them may be broken. Try updating the application to the latest version. If this does not help, the file cannot be restored using standard means.
It is also worth paying attention to the font settings. Technical documents often contain small text and complex tables. Pinch-zooming with two fingers may reduce readability. It is better to use the built-in settings of the reader and increase the basic font size, which will make the text clearer without losing the structure of the page.
Comparison table of popular readers
To make it easier for you to choose the right application, we have compiled a summary table of the characteristics of the most popular solutions. The data is based on the functionality of free versions of apps available at the time of writing.
| Application | Encoding support | Advertising availability | Additional. formats |
|---|---|---|---|
| CHM Reader | Auto + Manual | Minimum | CHM only |
| ReadEra | Full | No | PDF, EPUB, FB2 |
| CHM File Viewer | Auto | Yes | HTML, TXT |
| OlReader | Full | Yes | DOCX, DJVU |
As can be seen from the table, ReadEra is the undisputed leader in the absence of advertising and versatility. However, if you need an application that takes up minimal memory space and works exclusively with CHMthen a specialized CHM Reader would be a more optimal choice.
Universal readers are more convenient for those who read books of different formats, and specialized applications often work faster and more stable with a specific file type.
Frequently asked questions (FAQ)
Is it possible to open a CHM file without installing applications?
Theoretically, you can use online converters that convert CHM to PDF directly in the browser. However, this requires a stable Internet connection and uploading the file to a third-party server, which is not always safe for confidential documentation. Local opening without installing software on Android is impossible.
Why does the file open, but the table of contents is empty?
This is a common error in parsing the file structure. Try using a different reader, for example, switching from CHM Reader to ReadEra. Different engines interpret broken or non-standardly formed indexes inside the archive differently.
Is it safe to open CHM files from unverified sources?
Format CHM may contain executable scripts. Although on Android the risk of getting a virus through this format is lower than on Windows, it is still recommended to download technical documentation only from official websites of manufacturers or trusted resources.
How to transfer bookmarks from one application to another?
Unfortunately, there is no single standard for storing bookmarks between different applications. The data is usually stored in the internal database of each specific reader. When changing apps, reading progress and bookmarks will have to be installed again.
⚠️ Attention: Application interfaces and their functionality can be updated by developers. If you do not find the described setting, check the "About the application" section or the help inside the app itself.
Using the right tools turns reading complex technical documentation into a comfortable process. By installing one of the recommended readers, you get full access to the knowledge base, saved in CHMformat, right in your pocket.