Fast file content searches using IFilters

Last update 2022-05-31

Using IFilters for indexing library file contents

PDXpert indexes file contents within its Data\Library folder using components of the Microsoft Windows Indexing Service. Immediately after you copy a file into the library, the file contents are scheduled for indexing. Because indexing can take significant computing resources, files are indexed as a low-priority task.

You can expand the variety of indexed file types by installing software components (DLLs) called "IFilters". These are designed to parse files that you've checked into the PDXpert library. In many cases, you can download and install the IFilters from software publishers that define the file type you want indexed, or specialize in developing IFilters.

The PDXpert Filter Service uses Windows Search to index file attachments. In Windows Server 2016 and later, Windows Search is disabled by default. See Microsoft's instructions to enable the service.

All IFilters must be installed on the computer that hosts the PDXpert Application Server, and not on the PDXpert network client.

Install the correct 32-bit or 64-bit IFilter DLL for your server's operating system. Do not install a 32-bit IFilter on 64-bit Windows unless directed by the publisher. The PDXpert filter service supports both stream and file IFilters.

IFilter quality is uneven. Some IFilters are quite good: they parse file contents and properties accurately; support multi-threading; provide speedy results; return useful error diagnostics; and offer adequate technical documentation. Some are, frankly, not so good. If a specific IFilter is slow or inaccurate, contact the publisher to ensure you have their latest, or uninstall the IFilter and try another publisher's IFilter.

Common Windows IFilters§

You can view which files will be indexed by opening the Indexing Options utility (Start ➔ Control Panel ➔ Indexing Options, then click Advanced ➔ File Types). Recent versions of Windows and Windows Server include general-purpose IFilters. If your server computer has any of these IFilters installed, they're normally found in the C:\Windows\System32 or the related application's Program Files folder.

Filter name Description Typical extensions DLL
File Properties filter Unregistered file formats   query.dll
Favorites IFilter URL shortcut .url ieframe.dll
HTML Filter HTML / SHTML / ASP files .htm .html .asp .aspx .css nlhtml.dll
Microsoft Office Filter Office 97-2003 file types .doc .dot .ppt .xls .xlt offfilt.dll
Microsoft Office OneNote Filter1 Microsoft OneNote .one .onetoc .onepkg onfilter.dll
Microsoft Office Visio Filter1 Microsoft Visio .vsd .vsdx visfilt.dll
MIME Filter Mail formats .eml .nws mimefilt.dll
Office Open XML Format [appname] Filter1 Office XML-based file types .docx .pptx .xlsx offfiltx.dll
Office Outlook MSG Filter1 Microsoft Outlook files .msg msgfilt.dll
Open Document Format [extension] Filter1 Open Document formats .odp .ods .odt odffilt.dll
Plain Text Filter Plain-text files .cpp .csv .tab .txt .wri query.dll
Reader Search Handler Portable Document Format .pdf Windows.Data.Pdf.dll
Rich Text Filter Rich Text Format .rtf rtffilt.dll
Tiff Filter Class2 Tag image file format .tif .tiff tifffilt.dll
Wordpad [extension] Filter Wordpad files .docx .odt WordpadFilter.dll
XML Filter XML file types .csproj .xsd .xslt .xml xmlfilter.dll
XML Paper Specification Document Filter XML text file types .dwfx, .easmx, .jtx .xps xpsfilt.dll
Zip Filter1 Compressed file type .zip offfiltx.dll


  1. If these IFilters aren't installed, they may be offered through the Windows update service (components related to Windows Search), or by installing Microsoft Office applications. See also

  2. The Windows TIFF IFilter is a component of Windows installations. It provides optical character recognition (OCR) on images that conform to the Adobe TIFF specification. It is enabled using the Windows Features window:

    Windows Features TIFF IFilter

    You can download and install the Windows TIFF IFilter on older Windows systems:

Downloadable IFilters§

The installer for a replacement IFilter may not be capable of uninstalling itself, and/or may not restore the original IFilter that it replaced. You may need to use the original IFilter's installer to restore the previous IFilter.

To find IFilters, search the web for

  • windows ifilter [name] where [name] is the DLL you want, e.g., windows ifilter rtffilt.dll
  • windows ifilter [type] where [type] is the file type you want, e.g., windows ifilter dwg
  • windows ifilter [app] where [app] is the application you want, e.g., windows ifilter Excel

Office formats§

If you have Microsoft Office installed on the server, the Office IFilter is probably also installed. If you don't have Office installed on your server, you can download and install the IFilter to index these file types: .docx, .docm, .pptx, .pptm, .xlsx, .xlsm, .xlsb, .zip, .one, .vdx, .vsd, .vss, .vst, .vdx, .vsx and .vtx.

Corel publishes 32b/64b IFilters for its WordPerfect file format.

Adobe PDF§

The open-source SumatraPDF reader offers an installation option for a .pdf IFilter. Run the installer on the server computer, click the Options button, then mark the Let Windows Desktop Search search PDF documents checkbox.

PDF-XChange Co Ltd. offers a .pdf IFilter in the PDF-XChange Viewer application.

If you've installed the Adobe Reader XI on your 32-bit system, then the IFilter for .pdf files is already installed. However, you'll require a separate download for 64-bit systems. Unfortunately, there are many reports about installation difficulties.

A commercial .pdf IFilter is available from Foxit:

Compressed archive formats§

CiTekNet offers a number of IFilters for various files including .cab, .chm, .exe, .rar, and .zip formats.

CAD, graphic and other file formats§

OpenText has developed a TIFF (.tif) IFilter.

Autodesk offers an IFilter for Autocad DWG files (DWGFilt.dll) and Inventor (INVFilter.dll). These may be available only to licensed Autodesk users via the installer program.

IFilters for DWG, OpenOffice/StarOffice, RAR, and many others may be found on the IFilterShop website.

The QuiLogic Inc. IFilter indexes files containing XML data.

Ransdell Brown, Inc. publishes an IFilter for DWG files. (Note that the following download site is not the original publisher.)

Other IFilter resources§

To examine the IFilters installed on your server and the file types that can be indexed, obtain the IFilter Explorer from CiTekNet:

Technical information about design and implementation of IFilters:


This information and resources are listed as a convenience, but the listing is not an endorsement of the supplier, product or website. We do not receive compensation for any listing, test these products, nor provide support for any product listed. The IFilters' accuracy, performance, compatibility and licensing are determined exclusively by their publishers. Some IFilters have dependencies and prerequisites that should be verified before installation. We would appreciate learning of any additions or corrections to make this list more useful. Product names on these pages may be trademarks of other companies, and we make no claim to any of them.

This application note was relevant to the PDXpert software release that was current at time of publication. Product changes since that time may affect its utility. We'd be happy to assist you in assessing the applicability of this note to your situation.

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