Microsoft Windows Search Filter Host – High CPU on Windows 8 – FIXED (Look at your PDF iFilter)

(This was previously posted on another site I run [] and has proved very popular, so republishing here as well)

If you don’t want to read any of this article and just want to fix the problem that I found:


Quick Background Summary:

  • Got myself a Surface Pro 3 (core i5, 8GB RAM, 256GB SSD) while over in the US recently
  • VERY pleased with it (maybe another post about why another day)
  • BUT constant high CPU (30%+), heat and noise = poor battery life
  • Tracked the problem down to Microsoft Windows Search Filter Host via Task Manager
  • There are LOTS of articles about this (do a Google/Bing)
  • I tried everything that was suggested e.g. rebuild, remove XML from indexed data types etc etc etc etc
  • NOTHING solved to problem

Troubleshooting approach – how I found the culprit

Back to old fashioned troubleshooting.

  • I went to Control Panel and selected “All Control Panel Items” and then selected “Indexing Options”
  • Then selected Modifyimage
  • I then unselected all the locations and added them back in one at a time. Waiting until “Indexing Complete” showed before adding the next location.  All the time watching Task Manager and the Search Filter Host processimage
  • Long story short I kept going until after adding one of the locations the Search Filter Host process went to 30% ish and indexing progress appeared to hang.
  • So I removed the offending location from the “Indexed Locations” and ended the Search Filter Host process within Task Manager.  The process automatically restarts.  And we were back to “Indexing Complete”
  • I now started adding subdirectories of the offending location.  Again one at a time, waiting for Task Manager to blow out.
  • When I found a subdir that created problems I:
    • Removed it from Index Locations
    • Created a Temp directory
    • Added it to Index Locations
    • Copied each file from the offending subdir one at a time to the Temp dir and watched Task Manager

The Culprit

For me at least the culprit was PDF files.  Every time I added a PDF into the Temp directory, Task Manager would blow up.  (It may be that there are other file types that cause the problem, but this approach could be used to identify yours.)

To PROVE that PDFs were the problem I went into the “Advanced” part of Indexing Options and unchecked “PDF”.


I then added back in the offending location to the Index Locations and everything was good again and within a few minutes “Indexing Complete” with Task Manager showing the Search Filter Host using low resources when I was using the PC and grabbing more when PC was idle (just as I would expect.


Solving the Underlying Problem

CAVEAT – I have not double blind tested etc etc to prove this is correct. This may have nothing to do with Microsoft Reader – BUT this worked for me.  I may post a link to this Blog on some of the many other forums trying to solve this problem and let the wisdom of crowds do the next piece of the work.

Initial Clue:

I know from the past that some programs appear to have a hard coded need for Adobe Reader and not just any old reader.  Being a shiny new Surface Pro 3 I have just left Microsoft Reader software in place and didn’t install Adobe Reader.  As you can see from the screen grab above the icon next to “PDF” would suggest the Microsoft Reader is being used as the filter/handler for PDFs

Next Steps:

  • I un-installed Microsoft Reader
  • Then I installed the free Adobe Reader
  • I checked the “filter types to see if Adobe had now taken over the filtering duties.
  • AHHHHHH iFilter not found



  • After the reboot, Indexing seemed to have started up again and was showing as active but when I checked Task Manager resource usage was normal so I waited until indexing was complete
  • I now reselected PDF in the “Advanced Options/File Types” dialog


  • Then “Advanced Options/Rebuild


After a while with Task Manager using expected resources we arrived at “Indexing Complete”

Final Tidy Up

After all the messing around I wanted to make sure I put the index location, file types etc back to default.  Whilst “Rebuild Index” under “Index Options/Advanced will rebuild the index, it does not reset all the locations etc.  To do this I used one of the bits of guidance I had found during my initial research to solve the problem ( Method 4):

  • Start Regedit (all usual caveats and warnings associated with doing this given!!!)
  • Find the entry “SetupCompletedSuccessfully” in the root
  • Change the value from 1 to ZERO
  • Reboot – this will reset everything and rebuild your index
  • NB if you go straight in a look at the Index Locations then it may appear to be missing some e.g. Outlook, IE favourites), but as soon as these apps are started then they add themselves to the list of Index Locations

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