Blender animation file turn into "Textedit" file and never came out as a video I'm new in blender (I started in January 2018), this is the first time I try to get an animation and it still doesn't work "as expected".
I used JPEGs as frames when I rendered first into animation, after I created a new file in which I added them in the video editing mode.There is (only) 100 frames and the preview looks good. When I render the animation in the video editing mode, I finally get a file that is neither a .MP4, or a .avi, or .mov BUT a sort of "Textedit document".

To fix it I already try to change the output, the codec, the quality &amp; rapidity for the render. (even switched from blender render to cycles render too, to see if something different could happen)
I had this problem myself. You need to have File Extensions checked under Render: Output tab and then it will be saved in the correct file format - PNG in my case.