What Is a MIME Type?
In PDF/A, MIME types (also called media types) are used to identify the format of embedded files and associated files. They are stored in the embedded file stream's /Subtype entry and are required for PDF/A compliance when attachments are present. Examples include:
| File Type | MIME Type |
|---|---|
application/pdf | |
| XML | application/xml |
| TXT | text/plain |
| CSV | text/csv |
| JPEG | image/jpeg |
| PNG | image/png |
| TIFF | image/tiff |
| ZIP | application/zip |
In PDF/A documents, MIME types become important when files are embedded as Associated Files (AF) or traditional file attachments.
Why MIME Types Matter in PDF/A
PDF/A is designed for long-term archiving.
When a file is embedded, future software must be able to identify:
- What the embedded file contains
- How it should be processed
- Which application can open it
The MIME type provides this information.
Without a correct MIME type:
- Validation may fail
- Archival systems may misinterpret the file
- PDF/A compliance can be lost
Common MIME Types Used in PDF/A
Document Formats
|
File Type |
MIME Type |
|
PDF |
application/pdf |
|
PDF/A |
application/pdf |
|
Microsoft
Word (.doc) |
application/msword |
|
Microsoft
Word (.docx) |
application/vnd.openxmlformats-officedocument.wordprocessingml.document |
|
Rich
Text Format (.rtf) |
application/rtf |
|
OpenDocument
Text (.odt) |
application/vnd.oasis.opendocument.text |
|
Plain
Text (.txt) |
text/plain |
|
XML |
application/xml |
|
JSON |
application/json |
Spreadsheet Formats
|
File Type |
MIME Type |
|
Microsoft
Excel (.xls) |
application/vnd.ms-excel |
|
Microsoft
Excel (.xlsx) |
application/vnd.openxmlformats-officedocument.spreadsheetml.sheet |
|
CSV |
text/csv |
|
OpenDocument
Spreadsheet (.ods) |
application/vnd.oasis.opendocument.spreadsheet |
Presentation Formats
|
File Type |
MIME Type |
|
Microsoft
PowerPoint (.ppt) |
application/vnd.ms-powerpoint |
|
Microsoft
PowerPoint (.pptx) |
application/vnd.openxmlformats-officedocument.presentationml.presentation |
|
OpenDocument
Presentation (.odp) |
application/vnd.oasis.opendocument.presentation |
Image Formats
|
File Type |
MIME Type |
|
JPEG |
image/jpeg |
|
JPEG
2000 |
image/jp2 |
|
PNG |
image/png |
|
TIFF |
image/tiff |
|
GIF |
image/gif |
|
BMP |
image/bmp |
|
SVG |
image/svg+xml |
|
WebP |
image/webp |
CAD and Engineering Formats
Commonly attached in PDF/A-3, PDF/A-4, and PDF/A-4e documents.
|
File Type |
MIME Type |
|
STEP
(.stp, .step) |
application/step |
|
IGES
(.igs, .iges) |
model/iges |
|
JT |
model/jt |
|
STL |
model/stl |
|
OBJ |
model/obj |
|
IFC |
application/x-step or model/ifc (implementation
dependent) |
|
DWG |
image/vnd.dwg |
|
DXF |
image/vnd.dxf |
XML-Based Business Formats
|
File Type |
MIME Type |
|
Factur-X
XML |
application/xml |
|
ZUGFeRD
XML |
application/xml |
|
UBL
Invoice |
application/xml |
|
XBRL |
application/xml |
|
XBRL
Instance |
application/xbrl+xml |
Archive Formats
|
File Type |
MIME Type |
|
ZIP |
application/zip |
|
GZIP |
application/gzip |
|
TAR |
application/x-tar |
|
7-Zip |
application/x-7z-compressed |
Audio Formats
|
File Type |
MIME Type |
|
MP3 |
audio/mpeg |
|
WAV |
audio/wav |
|
OGG |
audio/ogg |
|
AAC |
audio/aac |
|
FLAC |
audio/flac |
Video Formats
|
File Type |
MIME Type |
|
MP4 |
video/mp4 |
|
AVI |
video/x-msvideo |
|
MOV |
video/quicktime |
|
MPEG |
video/mpeg |
|
WebM |
video/webm |
Best Practices
- Always use the official IANA-registered MIME type when available.
- Ensure the MIME type matches the actual file content.
-
For PDF/A-3, PDF/A-4, PDF/A-4f, and PDF/A-4e, every attachment should have a valid
/SubtypeMIME type. -
When embedding XML for Factur-X or ZUGFeRD, use:
application/xml
Official Source of MIME Types
The authoritative registry is maintained by the Internet Assigned Numbers Authority (IANA). PDF/A itself does not define a fixed list of allowed MIME types; it requires that the MIME type accurately describe the embedded file and preferably use a registered media type.
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