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Additional files


This page provides general information for authors creating additional files to maximize the quality of those files. It includes tips on handling files like these as well as supported formats.

How to use additional files

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Additional files are those that contain additional information which support or expand upon items referred to in the main manuscript.

Additional files will be linked to the final published article in exactly the same form you supplied them in, but will not be displayed within the article in this format.

You are encouraged to provide large data sets, tables or figures, movie files, software or other information as additional information. Results that would otherwise be indicated as "data not shown" can and should be included as additional files. Additional files are considered integral to articles published by BMC. There is no distinction between the main article and 'supplementary material'.

Figure files and tables should only be uploaded as additional files if they are too large. See tables (small, portrait, csv or excel) and figures (larger than one page).

Since weblinks and URLs frequently become broken, we require that all supplementary data are included as additional files rather than links to web pages. You should upload these files using the 'Additional material files' button in the manuscript submission tool.

Additional files published under and open access license in BMC journals are deposited in Figshare, to increase the discoverability and reuse of additional files and their related articles. Depositing additional files in Figshare also enhances the quality of articles’ appearance by making the files preview-able within the published article, and enables searching across additional files via More information on how Figshare supports journal article publishing is here. Please contact us with questions about additional file hosting in Figshare or if you are interested in publishing a data rich - with files of >20Mb – article.

Inserting and referencing

If additional files are provided, please list the following information in a separate section after the reference list:

  • File name (e.g. Additional file 1).
  • File format including the three-letter file extension (including name and a URL of an appropriate viewer if format is unusual).
  • Title of data.
  • Description of data.

Additional files should be named "Additional file 1" and so on and should be referenced explicitly by file name within the body of the article.

Additional files should be numbered in the order they are first mentioned in the text, and uploaded in this order.

File size and resolution

The maximum file size for additional files is 20 MB each and files will be virus-scanned on submission.

Data over 20 MB should be deposited in a suitable permanent repository for that type of data, where one exists (e.g. GEO for microarray data). Please see our list of recommended repositories for guidance.

Additional files can be submitted in any format.

Instructions for commonly submitted file types are available within guidelines for specific types of additional files.

Frequently asked questions

What are Additional files?
A. Additional files are files containing additional information that supports or expands upon items referred to in the main manuscript. All additional files must be referenced in the main manuscript.

What is the difference between an additional file and a figure file?
A. A figure file is an image file that will appear in the final published manuscript. On the other hand, additional files will be made available alongside the published manuscript, but will not be visible within it. Additional files should be named "Additional file 1" and so on and should be referenced explicitly by file name within the body of the article.

Can I upload my figures files as additional files?
A. The only time you should do this is when the figure image must be larger than A4 in order to be legible.

Why is it important to include additional files?
A. Additional information is considered integral to articles published by BMC. You are encouraged to provide data sets, tables, movie files, software or other information as additional information. Results that would otherwise be indicated as "data not shown" can and should be included as additional files.

How large can additional files be?
A. You should aim for all additional files to be as low a file size as possible. The maximum file size for additional files is 20 MB each.

Is there a limit to how many additional files I can include?
A. No; you can include as many relevant additional files as necessary.

Can I use image manipulation software to increase the clarity of images within additional files?
A. Enhancement of digital images using image-editing software is acceptable practice if carried out responsibly. However, it is crucial that artefacts are not introduced and the original data is not misrepresented.

Within my manuscript, can I make references to individual items within my additional files?
A. Yes, items within additional files can be referenced in the main manuscript. However, please use the format set out in the following example: “See Supplementary Table 1, Additional File 1”.

Can I submit earlier versions of the final manuscript as additional files?
A. No.

Can I cite references in additional files?
A. You can cite references in additional files, as long as you list them in a separate section within the additional file; any references that are only cited in the additional files should not be listed in the main manuscript reference list. 

Additional files formats

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This section provides information on which formats you should use for specific types of additional files.

Additional documentation and Algorithms

Additional documentation and algorithms can be provided in a number of formats, including PDF (Adobe Acrobat), DOC (Microsoft Word), TXT, RTF, EPS, HTML and PPT.

Animations and Movies

Animations can be provided in SWF (Shockwave Flash) format (or converted in a video format).

Movies in mp4, mpeg, mov, avi, swf and animated GIF formats will be embedded in the additional files page. The first frame of the movie will be used as 'poster frame' and will be shown before the user starts movie playback. Other formats will be available for download.

MOV is a common multimedia format, which is often used for saving movies and other video files. This format uses a proprietary compression algorithm developed by Apple Computer; compatible with both Macintosh and Windows platforms. MPG is a common digital video format, which typically incorporates MPEG-1 or MPEG-2 audio and video compression. AVI files can contain both audio and video data in a file container that allows synchronous audio-with-video playback.


Audio files can be uploaded in a number of formats, including: WAV, MP3, FLAC, AIFF and AU. WAV is a Microsoft and IBM audio file format standard for storing audio bitstreams. It is the main format used on Windows systems for raw and typically uncompressed audio.

Chemical Structures

CDX (ChemDraw) is the file format for saving chemical reaction schemes prepared using ChemDraw. Suggested ChemDraw settings are:

  • Chain Angle 120°
  • Bond spacing 18%
  • Fixed length 0.406 cm (11.5 pt)
  • Bold width 0.056 cm (1.6 pt)
  • Line width 0.018 cm (0.5 pt)
  • Margin width 0.046 cm (1.3 pt)
  • Hash spacing 0.071 cm (2 pt)

TGF (ISIS/Draw) is the file format for saving chemical reaction schemes prepared using ISIS/Draw.

Computational models

We encourage authors to prepare models of biochemical reaction networks using the Systems Biology Markup Language (SBML).

Generic Data Files

DAT (Data file) files are generic data files created by specific applications. They are not an ideal format to use, as they can typically only be accessed by the application that created the file. However, text within DAT files can sometimes be viewed using a text reader.

Geospatial Data

KML (Keyhole Markup Language) is an XML-based language schema for expressing geographic data in two or three-dimensions. KML can be used for geospatial biomedical data suited to 3D spatial visualisation. Google Earth will be used as a viewing application for KML data.

Genomic sequences

Genomic sequences should be formatted according to the Genomic Standards Consortium (GSC) and follow the minimum information about a genome sequence (MIGS) specification. The sequence should be deposited to the International Nucleotide Sequence Database Collaboration (INSDC) prior to submission and the accession numbers provided in the text of the manuscript.

Metabolic networks

Networks can be defined as a collection of interactions between different pairs of nodes. Frequently used formats include KML, BioPax, SBML , PSI-MI, SIF, XML and KGML.

Microarray data

The Minimum Information About a Microarray Experiment (MIAME) or Minimum Information about a high-throughput SeQuencing Experiment (MINSEQE) guidelines should be adhered to when reporting microarray data and we recommend using the spreadsheet-based MAGE-TAB format. We also recommend that you include a copy of the appropriate MIAME checklist.


Small self-contained websites can be submitted as additional files, in such a way that they will be browsable from within the full text HTML version of the article. In order to do this, please follow these instructions:

  1. Create a folder containing a starting file called index.html (or index.htm) in the root
  2. Put all files necessary for viewing the mini-website within the folder, or sub-folders
  3. Ensure that all links are relative (ie "images/picture.jpg" rather than "/images/picture.jpg" or "" or "C:\Documents and Settings\username\My Documents\mini-website\images\picture.jpg") and no link is longer than 255 characters
  4. Access the index.html file and browse around the mini-website, to ensure that the most commonly used browsers (Internet Explorer and Firefox) are able to view all parts of the mini-website without problems; it is ideal to check this on a different machine
  5. Compress the folder into a ZIP, check the file size is under 20 MB, ensure that index.html is in the root of the ZIP, and that the file has .zip extension, then submit as an additional file with your article

Tabular data

Tabular data can be provided in formats including: DAT, TXT, XLS, CSV, XML and TSV.