BIDS: The Brain Imaging Data Standard
A data standard to support the neuroimaging community
LAY SUMMARY
The Brain Imaging Data Structure (BIDS, ​www.bids-standard.org​) is a community-led standard
for organizing, describing and sharing neuroimaging data. Currently, it supports multiple
neuroimaging modalities including MRI, MEG, EEG, iEEG, with more to come. Multiple
applications and tools have been released to make it easy for researchers to incorporate BIDS
into their current workflows, maximising reproducibility, enabling effective data sharing, andsupporting good data management practices.

RATIONALE
Why is BIDS needed?
Neuroimaging experiments result in complicated data that can be arranged in many different
ways. Historically, data were organized differently between institutions and even within a lab.
This lack of consensus (or a standard) led to misunderstandings and suboptimal usage ofresources: 1) human (time wasted on rearranging data or rewriting scripts expecting certainstructure; 2) infrastructure (data storage space); 3) financial (disorganized data has limited
longevity and value after first publication). Finally, it produces poor reproducibility of results,
even within the lab where data were collected. The Brain Imaging Data Structure (BIDS) has
provided the neuroimaging community with a simple and easily adopted way of organizing
neuroimaging data.
What is BIDS?
The Brain Imaging Data Structure (BIDS) is a community-led standard for organizing,describing and sharing neuroimaging data. Its goal is to make neuroimaging data moreaccessible, shareable, and usable by researchers. To achieve this goal, BIDS provides a simple
and intuitive way to organize and describe neuroimaging data and associated data andmetadata. BIDS is based on simple file formats (often text-based) and folder structures thatcan easily be adopted by any researcher around the world with minimum effort. BIDS is not a
file format, but instead relies upon common standard file formats (e.g. nifti, json, tsv). BIDS
has two major components. First, it specifies a naming convention for files and directories.
Second, it specifies conventions for the organization of metadata. A ​robust validator allows
researchers to easily check whether a dataset meets the standard.

Key to success
BIDS has three foundational principles: 1) to minimize
complexity and facilitate adoption, reuse existing
methods and technologies whenever possible; 2) tackle
the most commonly used neuroimaging data, derivatives,and models (inspired by the Pareto principle); 3) enabling
and maximizing community engagement in the creationand extension of the specification, to ensure maximal
adoption by the research community.

SIGNIFICANCE
Benefits of BIDS1) Efficient data usage: The use of a common format
allows data to be more easily reused by otherresearchers, maximizing its utility. 2) Analysis pipelines:
there is a growing number of ​data analysis software
packages (BIDS-Apps) that can automatically processdata organized according to BIDS; 3) Data sharing: Use ofBIDS makes sharing by major repositories (e.g.
OpenNeuro) very simple, enabling rapid and effective data
sharing.
BIDS neuroimaging modalities currently supported
The BIDS standard was first established for MRI and fMRI
in 2015 (Gorgolewski et al. 2016). BIDS is based on
simple file formats (often text-based) and folder
structures that can readily expand to additional data
modalities. BIDS was heavily inspired by the format usedinternally by the OpenfMRI repository that is now known
as OpenNeuro. Following the initial success of MRI BIDS
and associated BIDS Apps, there was a clear need forextensions into other modalities. In 2016, an international
consortium proposed an extension of BIDS for
Magnetoencephalography (MEG) datasets (Niso et al.
2018). The MEG-BIDS extension highly contributed tofurther extend BIDS to other electrophysiological data
modalities. The electroencephalography (EEG) extension(Pernet et al. 2019) and the intracranial EEG (iEEG)
extension (Holdgraf et al. 2019) were soon released.
Currently, there are 24 active extension proposals
spanning several imaging modalities, derivative products,and data types (represented in Tables 1 and 2). We arepreparing to accept the Arterial Spin Labeling (ASL) and Positron Emission Tomography (PET)extensions into BIDS.
While working on BIDS we consulted many neuroscientists to make sure it covers mostcommon experiments, but at the same time is intuitive and easy to adopt. The specification isintentionally based on simple file formats and folder structures to reflect common labpractices and make it accessible to a wide range of scientists coming from different
backgrounds.

APPROACH
BIDS is a community effort
BIDS is developed by the community for the community and everybody can become a part ofthe community.
The BIDS Organizational Design
The BIDS organization is a community of brain researchers that strives for consensus
decision making. The BIDS organization primarily produces the BIDS-Specification along withsupporting BIDS-aware tools and community. Our organizational design works in tandem with
our governance structure to describe the BIDS environment, and it is based on three pillars: 1)
Standard​: related to the BIDS Specification and BIDS Extension Proposals (BEPs); 2) ​Tools​:
BIDS Apps and BIDS-aware software; and 3) ​Collaboration​: BIDS community. Ourorganizational design is driven by three principles: Sustainability, Robustness, and Inclusivity.
See more at: B​ IDS Organization​.
BIDS GovernanceTo achieve the goals of widespread adoption of the standard while growing to adapt to its
community of members, BIDS is led by a series of groups presented in Figure 2. See more at:BIDS Governance​.

Principles for open standards development
The BIDS approach to standards development follows the principles of the ​Modern Paradigm
for Standards developed by OpenStand: 1) respectful cooperation between standardsorganizations, 2) adherence to fundamental principles of standards development: dueprocess, broad consensus, transparency, balance, openness, 3) collective empowerment, 4)availability, 5) voluntary adoption.

EVIDENCE OF IMPACT
Since its origin, the BIDS has revolutionized the way in which neuroimaging research is done.
BIDS has a community of 136 credited contributors (22 female, as of October 3, 2020) (​link​),with ~10,000 users visiting ​the website​, and ~7,000 users exploring the ​BIDS Specification​,over the past 6 months (see Figure 3). We have organized over 100 worldwide educational
workshops and presentations at conferences over the last year (see e.g. BIDS presence atOHBM​). Over 404 journal articles have ​cited BIDS or any of its extensions. Currently, more than
60 ​reported centers, institutes and databases around the world have implemented BIDS as
their organizational structure. As of October 7, 2020, we have 196 people signed up for ourBIDS email list and 414 members on our google group.