File Format Recommendations for Supplemental Files
Some file formats will be difficult or impossible to use in the future. The file formats with the best chance of survival have open specifications, are high quality, and are in relatively wide use. Ensuring these formats can be accessed or read in the future is key to their long-term preservation.
The University Libraries manages Arch, a digital repository. You can use this service to deposit any supplemental files you created for your dissertation research that you’d like to make available to the public, including data, code, figures, presentations, and media.
- Log in to Arch with your NetID
- Create a Work to contain your supplemental files (one Work can have many files)
- Describe and upload your files (including any README files to assist others)
- Reference these files in your dissertation using the DOI that Arch assigns to your deposit.
Please follow these recommendations when making format choices. Also, make sure the format is an uncompressed version, highest quality compressed version, or the final production version. This will help maximize potential for long term preservation and accessibility.
Unfortunately, it's not possible to provide a single list of file formats that are appropriate for all use cases, but this list is a good starting point. Please exercise caution when using proprietary formats and digital rights management (DRM) software that may make viewing content difficult or impossible to access in the future. If you have any questions, please email the University Libraries at library@northwestern.edu. Your question will be routed to staff with the appropriate staff to help you.
Simplified Guidelines/File Format Recommendations
- Audio — Highly recommended: AIFF (.aif, .aiff) or WAV (.wav) . Moderately recommended: MP3 (.mp3), AAC (.mp4, .mp4a, .aac), FLAC (.flac) or ALAC (.m4a).
- Video — Highly recommended: Uncompressed Quicktime Movie (.mov); uncompressed AVI (.avi). Moderately recommended: MPEG-1, MPEG-2 or MPEG-4 encoded video (.avi, .mpg, .mpeg, .mov, .mkv, .mp4).
- Virtual Reality/3D — Highly recommended: X3D (.x3d). Please talk with a Northwestern Digital Librarian to determine best output settings and format.
- Image - Highly recommended: Full color images @ 600dpi or higher saved as JPEG2000 Lossless (.jp2) or TIFF 24-bit, uncompressed (.tif, .tiff). Moderately recommended: lossy compressed formats limited to JPEG (.jpg, .jpeg), JPEG2000 (.jp2), TIFF (.tif, .tiff), or PNG (.png) at highest quality possible.
- Text - Highly recommended: Open Document Text (.odt), UTF-8 Unicode text (.txt), or PDF/A (.pdf). Moderately recommended: Markdown (.md), Rich Text Format (.rtf).
- Presentation - Highly recommended: Open Document Presentation (.odp). Moderately recommended: PDF/A (.pdf) for images only.
- Spreadsheet - Highly recommended: Open Document Spreadsheet (.ods). Moderately recommended: Comma separated value CSV (.csv) or Tab-delimited text file (.txt).
- Code – Highly recommended: non-proprietary source code (*.c, *.R, *.sh, *.js, *.jsp, *.java, *.pl, *.py, etc.). Moderately recommended: proprietary commercial software (*.m, *.mat, *.do, etc.). Source code managed using a version control system, such as Git, can be compressed to a .zip, .tar, .tar.gz archive format and deposited to Arch for preservation.