A .map
file allows you to map a minimized javascript file ( minified ) to the original file. So we can debug a webpage without having to change the system on the server, that is:
- No more gambiarras to put the original jQuery in "development" mode and jQuery min in production mode
- The code executed in the browser remains minified , but you can see the equivalent orignal snippet so you can understand what is happening
There are other details, advantages, and applications you can read in Introduction to JavaScript Source Maps .
As for Chrome, it tries to download the map whenever it finds a reference in the javascript file. Example:
/*! jQuery v1.10.2 | (c) 2005, 2013 jQuery Foundation, Inc. | jquery.org/license
//@ sourceMappingURL=jquery-1.10.2.min.map
*/
To avoid errors, remove the snippet from the Javascript file or disable this feature from the browser using the Enable Source Maps
option, as shown below (extracted from the article quoted):