File formats

The choice of the appropriate file format is crucial for the accessibility and reusability of your data.

  • An open format is a file format that can be used by anyone, as its specifications are publicly available.
  • A proprietary (or closed) format is a format that is tied to a particular vendor's software. When the software is no longer available, the files usually become unusable and/or unreadable.

We therefore recommend that you save your data in an open format whenever possible. And if converting to an open format will alter the form of the document, then it is worth keeping the data in both proprietary and non-proprietary formats.

Recommended practices

The following table lists the recommended and acceptable formats for various types of data.

Type of dataRecommended formats
Acceptable formats

Tabular data with extensive metadata

variable labels, code labels, and defined missing values

SPSS portable format (.por)

delimited text and command ('setup') file (SPSS, Stata, SAS, etc.)

structured text or mark-up file of metadata information, e.g. DDI XML file

proprietary formats of statistical packages: SPSS (.sav), Stata (.dta), MS Access (.mdb/.accdb)

Tabular data with minimal metadata

column headings, variable names

comma-separated values (.csv)

tab-delimited file (.tab)

delimited text with SQL data definition statements

delimited text (.txt) with characters not present in data used as delimiters

widely-used formats: MS Excel (.xls/.xlsx), MS Access (.mdb/.accdb), dBase (.dbf), OpenDocument Spreadsheet (.ods)

Geospatial data

vector and raster data

ESRI Shapefile (.shp, .shx, .dbf, .prj, .sbx, .sbn optional)

geo-referenced TIFF (.tif, .tfw)

CAD data (.dwg)

tabular GIS attribute data

Geography Markup Language (.gml)

ESRI Geodatabase format (.mdb)

MapInfo Interchange Format (.mif) for vector data

Keyhole Mark-up Language (.kml)

Adobe Illustrator (.ai), CAD data (.dxf or .svg)

binary formats of GIS and CAD packages

Textual data

Rich Text Format (.rtf)

plain text, ASCII (.txt)

eXtensible Mark-up Language (.xml) text according to an appropriate Document Type Definition (DTD) or schema

Hypertext Mark-up Language (.html)

widely-used formats: MS Word (.doc/.docx)

some software-specific formats: NUD*IST, NVivo and ATLAS.ti

Image data

TIFF 6.0 uncompressed (.tif)

JPEG (.jpeg, .jpg, .jp2) if original created in this format

GIF (.gif)

TIFF other versions (.tif, .tiff)

RAW image format (.raw)

Photoshop files (.psd)

BMP (.bmp)

PNG (.png)

Adobe Portable Document Format (PDF/A, PDF) (.pdf)

Audio data

Free Lossless Audio Codec (FLAC) (.flac)

MPEG-1 Audio Layer 3 (.mp3) if original created in this format

Audio Interchange File Format (.aif)

Waveform Audio Format (.wav)

Video data

MPEG-4 (.mp4)

OGG video (.ogv, .ogg)

motion JPEG 2000 (.mj2)

AVCHD video (.avchd)

Documentation and scripts

Rich Text Format (.rtf)

PDF/UA, PDF/A or PDF (.pdf)

XHTML or HTML (.xhtml, .htm)

OpenDocument Text (.odt)

plain text (.txt)

widely-used formats: MS Word (.doc/.docx), MS Excel (.xls/.xlsx)

XML marked-up text (.xml) according to an appropriate DTD or schema, e.g. XHMTL 1.0

Source: UK Data Service.


See also the Best practices for file formats from the Stanford Library.