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Aug 29, 2026
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X Codec Inspector is a free portable tool listing every DirectShow filter and Media Foundation Transform on your PC, with the CLSIDs, merits and media types you need to find the codec conflict behind a playback failure.
A codec pack goes in, and a media player that worked yesterday suddenly refuses a file it has always played.
The cause is almost always two decoders registered for the same media type, with the wrong one winning.
Diagnosing that used to mean a commercial tool or a long afternoon in the registry.
X Codec Inspector maps your entire DirectShow and Media Foundation environment in seconds, from a free portable executable.
What X Codec Inspector Does
It reads the Windows registry and loads every registered DirectShow filter and every Media Foundation Transform on the system. For each one it shows the CLSID, the DLL path, the file version, the company name, the merit value, and every supported media type and pin direction.
Both 32-bit and 64-bit filters are listed, marked as such. There is nothing to install - run the executable and everything is visible immediately.
The two tabs cover two different layers of Windows. DirectShow is the older pipeline, used by Media Player Classic Home Cinema, Windows Media Player and most third-party decoders including LAV Filters.
Media Foundation is the modern one, used by Windows 8 and later, and it handles hardware-accelerated decoding for H.264, HEVC and AV1 through Intel Quick Sync, NVDEC and DXVA.
New in 1.2 - Open a Filter's Own Settings
Version 1.2 adds a Properties button that opens the settings dialog built into the filter itself - the same pages it would show inside a media player or editor.
The LAME DirectShow Filter is the clearest example. Select it, click Properties, and you get its bitrate, channel mode and quality controls, without needing an application that exposes them.
Two things to expect. Most filters have no property pages at all, which is normal rather than a fault, and the tool will say so. Where pages do exist, settings only persist if the filter saves them itself - many apply to the running instance and forget.
Where It Fits in Your Codec Workflow
The tool earns its place at the diagnostic stage: after something has broken, or before you change something you may need to reverse.
Step 1 - take a baseline. Before installing a pack such as K-Lite Mega Codec Pack or a standalone DirectShow FilterPack, click Snapshot. It records every registered filter and MFT.
Step 2 - install, then compare. Afterwards click Reload, then Compare Snapshot. The comparison highlights every filter added in green and every one removed in red, so you can see exactly what the installer did.
Step 3 - resolve the conflict. Click Detect for the list of media types handled by more than one filter, ranked by severity. Then use Edit Merit to demote the filter you do not want, without uninstalling anything.
Why demoting beats uninstalling. A merit change is fully reversible and leaves the filter registered, so if you guess wrong you set it back. Unregistering a filter that something else depends on is a harder mistake to undo.
Merit Values Explained
Merit is how DirectShow decides which filter wins when several can handle the same media type. The order runs PREFERRED (0x800000), then NORMAL (0x600000), then UNLIKELY (0x400000), then DO_NOT_USE (0x200000).
If FFDShow and LAV Filters are both registered for H.264 and FFDShow has the higher merit, FFDShow is chosen even when LAV Video is the better decoder. Dropping FFDShow to UNLIKELY fixes it without touching the registry by hand.
That is the difference between smooth hardware-accelerated playback and a black screen when following a setup guide such as Transform Your Media Player with LAV Filters.
DO_NOT_USE does not mean broken. Encoders are deliberately registered at that level so Windows never selects them automatically, and an application picks them explicitly instead. Seeing it on an encoder is correct, not a problem to fix.
The Health Check and DLL Scanner
Health Check scans every registered filter and marks in red any whose DLL is missing from disk.
Those broken registrations are a common cause of playback errors and crash-on-open behaviour, and they accumulate quietly as packs are updated, removed badly or overwritten. The scan makes the whole set visible in one pass.
It also catches a subtler case: a filter registered from a folder that still exists but should not be permanent, such as a Downloads directory. Those work until the folder is tidied.
When You Need It Most
Four situations where it saves real time.
- After installing or updating K-Lite Codec Pack, when a format that previously worked stops playing.
- After a Windows update that changes Media Foundation components and disrupts hardware decoding.
- When setting up HEVC on a fresh system - the guide on playing HEVC files with LAV Filters covers the codec side, and this verifies the registration took.
- When a DTS/AC3/DD+ Source Filter install collides with an audio decoder you already had.
If playback is working but not accelerated, the guide on hardware acceleration in MPC-HC is the better starting point, and the Best Codec Packs guide covers which packs work well together.
System Requirements
It runs on Windows 7, 8, 8.1, 10 and 11, in both 32-bit and 64-bit editions.
Admin rights are not needed for browsing, searching, exporting or snapshots. Windows prompts for elevation only when you use Register DLL, Unregister DLL or Edit Merit, because those write to protected parts of the registry.
Export covers HTML, CSV and JSON, which makes it easy to record your filter state or send it to someone helping you.
Quick questions
Is X Codec Inspector free?
Yes, with no paid tier and nothing bundled. It is a portable executable from the same team as X Codec Pack, and it needs no installation.
Will it break my codecs?
Not by browsing. Everything except Register DLL, Unregister DLL and Edit Merit is read-only, and merit changes are reversible by setting the value back.
Why does the Properties button do nothing on some filters?
Because most filters do not implement property pages, which is optional and entirely up to the filter's author. The tool tells you when there are none rather than failing silently.
Why did my property page settings not stick?
Many filters only apply settings to the instance that is running and forget them when it closes. Whether they persist is the filter's decision, not something the tool controls.
What does DO_NOT_USE mean next to a filter?
That Windows will never choose it automatically. On encoders that is deliberate and correct, because applications are expected to select an encoder explicitly rather than have one picked for them.
How is it different from the other codec listing tools?
GSpot and MediaInfo analyse media files, telling you what is inside a particular video.
This lists what is installed on the system instead, which is closer to DirectShow Filter Manager or DSF/MFT Viewer, with conflict detection and merit editing added.
More tools of this kind sit in the Codec Identifiers section.
Download X Codec Inspector 1.2 and see what is registered on your PC, or tell us how you got on if you have used it before.
