A validator for LibriVox audio files

Checker is an open source tool that looks for common problems with recordings for LibriVox, a site where volunteers collaborate to make audio books of public domain texts. Checker saves time by checking contributions for common issues before files are uploaded.

Checker will check…

…volume, encoding options, audio format, metadata (ID3 tags), and file name conventions.

Checker won’t check…

…the content of the recording (such as reading the wrong word) or the quality of your performance.

To use Checker, drag-and-drop MP3 files (or a folder or ZIP archive) onto the window, then wait for it to analyze them. Once done, click a file name to see a report of any issues that it found. The report will either state that the file “passed” or else list any issues as errors or warnings. Errors are serious problems that should be fixed before uploading the file. A warning is less serious, or in some cases a potential problem that Checker is not sure about.


Checker is written in Java, so it runs on many popular platforms. The Windows and macOS installers will automatically try to install Java for you if necessary, but if that fails you can also install it yourself.

Current version—0.96 (January 28, 2014)


Windows: Download and run the installer as you would any other Windows software. Download either the 32-bit or 64-bit version, depending on whether you have the 32-bit or 64-bit version of Java installed. If in doubt, use the 32-bit installer. On some versions of Windows, you may be shown a warning about the software being from an unknown publisher and you will have to give explicit permission to run the installer.

macOS: Download the DMG file. To open the installer under OS X 10.8 (Mountain Lion) or newer, you must control-click (or right click) the file and choose Open from the displayed popup menu. Then, click the Open button again in the displayed dialog box. When the disk image opens, double click the enclosed installer and follow the prompts.

Linux: Download and unzip the file, then run the checker script to start the application.


January 28 2014 (0.96)

May 23 2013 (0.95)

May 20 2013 (0.94)

May 11 2012 (alpha 0.93)

April 1 2012 (alpha 0.9)

January 6 2009 (alpha 0.2)

October 29 2008 (prototype 1)

Source Code

Download checker-0.96-src.7z

This program uses the JavaLayer library for decoding MP3 audio and the Jaudiotagger library for parsing ID3 metadata. Both of these are made available under an LGPL license and they are included with the source package for convenience.