What is the SPL file format?
.spl files are generated automatically by the Windows operating system during the printing process.
What kind of data do .spl files store?
Windows saves print-job data to .spl files while a document is being printed. By default the spooler wraps page content in EMF (Enhanced Metafile Format) records, keeping the data device-independent until it reaches the printer. With certain print processors the file holds RAW device-ready data instead - the printer's own language (PCL, PostScript, or PJL) passed through without conversion. Once the printing process finishes, the .spl file is deleted. .spl files therefore act as a temporary data buffer between the operating system and the printing device.
What are EMF and RAW spool formats?
The default EMF format stores page content as Enhanced Metafile records, which lets the spooler return control to the application quickly while rendering continues in the background. The RAW format passes printer-language data directly to the device without re-rendering - a common choice for barcode and label printers that consume language data natively. RAW bypasses additional driver processing and can reduce rendering overhead on compatible hardware.
Where are .spl files stored?
Windows saves .spl files to the system print spooler folder C:\Windows\System32\spool\PRINTERS. Each .spl file is paired with a .shd shadow file in the same folder that holds job metadata such as owner, priority, and data type. Because the .spl file is deleted after the printing operation finishes, both files disappear automatically on success. A .spl file that persists in the folder - together with its .shd companion - usually signals a stuck print queue entry that must be cleared manually.
Security & safety
RISK: MEDIUMThe .spl file itself is inert print data, but it has two real-world risks. (1) Privacy/forensics: an .spl can contain a full rendering of whatever was printed, so leftover spool files may leak sensitive documents - clear the spool folder on shared/disposed machines. (2) The Windows Print Spooler service that processes .spl files has been the target of serious vulnerabilities (notably 'PrintNightmare', CVE-2021-34527, 2021), so keep Windows updated. Manually deleting .spl/.shd files is safe only when the Print Spooler service is stopped first; deleting them while it runs can corrupt the active queue. Also avoid sketchy third-party 'SPL viewer' downloads from unknown sites.
Format details
in a nutshell- FutureSplash Animator / Shockwave Flash player movie - Legacy .spl is a FutureSplash (pre-Flash) or Shockwave Flash format - a different format from the print spool file; both Flash-era and now obsolete (open with Ruffle if at all).
- FontLab / Sound / other app data - Some applications (e.g. FontLab, certain audio/CAD tools) have used .spl for their own data, opened only by the originating software.
Programs that open SPL files
Windows3 apps
Print Spooler service (the OS itself)
Built-in The .spl is consumed by Windows automatically. To clear stuck files: services.msc -> stop 'Print Spooler' -> delete *.spl and *.shd in C:\Windows\System32\spool\PRINTERS -> start the service.
EMF Printer Spool File Viewer (CodeProject)
Free Open-source utility that renders an EMF-type .spl so you can see the print job's content (troubleshooting/forensics). Does not work on RAW-spooled files.
O&K Printer Viewer / SPL Viewer tools
Freemium Third-party SPL/EMF spool viewers that display, re-print or export queued spool jobs. Use reputable vendors only. Technical details
deep spec| Payload format | EMF (Enhanced Metafile) page records by default; RAW pass-through (PCL, PostScript, PJL) when the print processor uses direct spooling |
| Encoding | Binary - EMF metafile records or raw printer-language bytes, depending on the spool data type selected by the print processor |
| Byte order | Little-endian (EMF record headers follow the Windows ENHMETAHEADER structure) |
| File signature | No fixed universal magic bytes; EMF-spooled jobs open with EMF record type 0x01 0x00 0x00 0x00; RAW jobs begin with the printer language marker (e.g. %-12345X for PJL, %!PS for PostScript) |
| Compression | None - EMF records and RAW payloads are stored as-is without additional compression |
| Encryption | None - contents are plain binary, protected only by NTFS file-system permissions on the spool folder |
| Typical file size | Tens of KB to hundreds of MB, scaling with page count, graphics complexity, and print resolution |
| Storage location | Fixed OS path: C:\Windows\System32\spool\PRINTERS - not user-configurable without registry edits to the DefaultSpoolDirectory value |
| Companion file | Always paired with a .shd shadow file of the same numeric base name, which stores job metadata (printer name, owner, priority, data type) |
| File lifespan | Transient - created when a job enters the print queue and deleted automatically upon successful completion |
| Color support | Inherits the print job's color data; EMF payload can carry full-color device-independent bitmaps at any bit depth |
| Naming convention | Named by the spooler with a sequential numeric base (e.g. FP000001.SPL), matching the base name of its paired .shd file |
| Associated OS | Windows only - part of the NT print spooler subsystem present in every Windows release from NT 3.1 through Windows 11 |
| Stuck-queue indicator | A .spl file remaining in the spool folder after printing finishes (alongside its .shd) indicates a paused or failed job; clearing it typically requires stopping and restarting the Print Spooler service |
| Released | Windows print spooler architecture (NT-era and onward) |
| Latest version | N/A - internal OS spooler file; format is EMF-based or pass-through RAW depending on the print processor |
| Specification | learn.microsoft.com |
SPL conversions
Community Q&A
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