KMPlayer Doesn't Play MP4, FLV, MKV Files Problems [Solved]

[Latest Updated: Nov. 26, 2018 by Estrella H. to Playing Media]


KMPlayer Doesn't Play MP4, FLV, MKV Files Problems [Solved]

Q 1: - My KMPlayer doesn't play MP4 file. KMPlayer can't play an .mp4 file I just downloaded from YouTube. I tried to use other media players (VLC, GOM, WINAMP), but none of them works. So I downloaded the video again and again, which does not fix the KMPlayer MP4 file opening error neither. So how to solve the problem that KMPlayer can't play MP4 files?

Q 2: - I cannot use my KMPlayer to play the .mp4, .flv and .mkv files. I have no problem playing these files using KMPlayer before I reinstall the WINDOWS XP operating system. Right now I have the KMPlayer, can anybody tell me how to fix the KMPlayer error of cannot play MP4, FLV, MKV?

How to Solve KMPlayer Doesn't Play MP4 Prob?

Best KMPlayer Alternative - 5KPlayer
Supports 450+ video formats, MP4, MPEG, AVI, MOV, FLV, etc.

For Windows and Mac only. If you are a mobile user, please click here.

KMPlayer (on Wiki) - A highly-praised free media player for Windows which can play a long list of video formats including AVI, ASF, WMV, AVS, FLV, MKV, MOV, 3GP, MP4, MPG, MPEG, DAT, OGM, VOB. The latest version of KMPlayer is KMPlayer So if your KMPlayer does not play MP4, first try to upgrade it to the latest edition.

Why KMPlayer Doesn't Play MP4 Files

The problem that KMPlayer cannot play MP4, FLV or MKV files can be caused by several factors including the lack of MP4 codec pack, the settings on your computer, the problem of your YouTube downloader or the KMPlayer itself, etc, based on which solutions for how to solve "KMPlayer doesn't play MP4" prob will be divided into three parts.

Part I - How to solve "KMPlayer doesn't play MP4" problem by adjusting computer settings

Surely KMPlayer is capable of playing .mp4, .mkv and .flv videos. But if your installed KMPlayer doesn't work or can't open MP4, FLV or MKV files, probably your computer lacks the codec to play these videos. So to solve the "KMPlayer doesn't play MP4" problem, you can try to activate Script Active X of Windows by doing as follows:

1. Click the Start Menu, type "Internet Option" in the search box and open it up.
2. Choose Security -> Click Custom level -> Find "Script ActiveX controls and plug-ins" -> Select Enable for all under this category -> Click button OK to close the window.
3. Uninstall Adobe Flash Player and get it reinstalled. That's it. And then you should be able to use your KMPlayer to watch MP4 videos.

Part II – "KMPlayer doesn't play MP4" problem caused by YouTube downloader

If you've changed the computer settings, but still can't play MP4/FLV YouTube downloaded videos with KMPlayer, maybe the problem is the YouTube downloader you are using. The file you have is either corrupted or mislabeled. So how to solve the problem that KMPlayer doesn't play MP4 for inappropriate choose of YouTube downloading tools? Try some free yet professional YouTube downloader alternatives, such as WinX YouTube Downloader, which provides safe and fast download of YouTube 4K UHD videos (1080p, 3D, SD) in FLV/MP4 format, YouTube full movies and kids songs, etc, to avoid "KMPlayer cannot play MP4" problem caused by incomplete download.

[Solved] KMPlayer doesn't play MP4 file
1. Download WinX YouTube Downloader on your PC (100% clean and free).
2. Click button "+" to add a YouTube video URL, and analyze it.
3. Select your desired resolution, quality or file size and choose MP4 as the output format
4. Click OK, specify the Target Folder and hit Download button to fully download your MP4 video.

Solve KMPlayer Cannot Play MP4 Problem

Part III - Fix "KMPlayer doesn't play MP4" error by using KMPlayer alternatives

KMPlayer and VLC media player should have no trouble playing MP4, FLV, MKV videos. If your KMPlayer doesn't play MP4 Video, probably it was not successfully installed. In this case, install the new version of KMPlayer to play MP4 videos again. Or go to Options -> Preferences -> Filter Control and check the Source Filters, Splitters, and Internal Video (and audio) Decoders.

Well, there are also many other media players that can play MP4 video very well if your KMPlayer still can't play MP4 after all those efforts, one of which available for free is 5KPlayer (for Windows/Mac).

5KPlayer supports all video audio codecs, including:
1. Supports popular formats MP4, H.264, M4V, WEBM, MPEG1/2, WMV/ASF, AVI, MOV, RM, OGV, FLV;
2. 1080P HD videos like M2TS, AVCHD, TP, MPEG-TS, EVO, MKV, AVC, MOD;

Besides, 5KPlayer is an all-in-one media player that can free download MP4/FLV/3GP/WebM videos songs from 300+ video sites, stream (MP4/MOV/M4V) videos music for AirPlay-supported devices, play regular and commercial DVDs, etc.

KMPlayer Alternative

Want to get an all-in-one media player that can play MP4, MKV, FLV and more video files directly and smoothly? 5KPlayer is your best option.

VideoProc Box


Best video/music downloader & converter, video editor, DVD converter, video/webcam recorder for Windows (10) and Mac. Ultrafast video processing speed with Nvidia/Intel/AMD hardware acceleration.

For PC and Mac only. Go to mobile page.

How to Use | Contact Support | Learn More

About the Author

   Estrella H.@hl_estrella

Estrella H. is a senior editor in Digiarty Software. She manages the software test section and creates easy and useful how-tos. When not in editing, she spends her spare time on Rubik's Cube and ukulele.

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