Written and maintained by CASRAI Editorial Board
Last updated
ASCL is the Astrophysics Source Code Library, a free online registry and repository for source codes of interest to astronomers and astrophysicists, at ascl.net. This page explains what it holds, who runs it, how a code gets an ascl: identifier, how to cite one, and where it sits next to general-purpose software archives (facts checked against ascl.net on 2026-11-08).
What the ASCL is
The ASCL describes itself as a free online registry and repository for source codes of interest to astronomers and astrophysicists, including solar system astronomers. It has worked to make codes used in research discoverable since 1999. Its entries are codes that appeared in, or were submitted to, peer-reviewed publications.
It is a registry first. Each entry is a record that points to where a code can be downloaded, with a description, the author names and a link to a research paper that uses the code. Where a code has no download site, the ASCL can house an archive file itself. Every entry receives a unique ASCL identifier, and an entry can be linked by prefixing its ID with ascl.net/.
Who runs the ASCL and what it covers
According to a paper by ASCL staff, Ten (or more!) reasons to register your software with the ASCL (arXiv:2412.19941), the library was established at Michigan Technological University in 1999 by Robert Nemiroff and John Wallin. That paper reported over 3,500 entries, cited over 17,000 times, as of its late-2024 writing; the figures will have moved since.
Scope is astronomy and astrophysics software. A code does not have to be in the public domain to be listed, so closed-source or restricted-licence codes can still be registered, provided they meet the submission requirements below. The ASCL is indexed by the SAO/NASA Astrophysics Data System (ADS) and by Web of Science; through ADS its entries also surface in Google Scholar.
How to find, cite and register a code
Finding codes
The site navigation offers Browse (the full list at /code/all), Resources and Submissions.
Citing an ASCL entry
Entry IDs have the form ascl:yymm.xxx. The ID can be used in a reference list to cite the software itself rather than only a paper about it. Each entry also carries a “Preferred citation method” field, in which the code author states how they want to be credited; follow that field when it is filled in. An ASCL ID is a registry identifier, not a DOI; see DOI links for how DOIs resolve, and the CITATION.cff format for putting citation instructions in a repository.
Registering a code
The Submissions page lists what a submission needs and three ways to send it:
- Prepare the code name and the author(s).
- Write a short description of what the code does.
- Supply a download URL (or send an archive file if no download site exists).
- Supply a link to a research paper that uses the code.
- Submit through one of three routes: the online form at
/code/submit; import of a codemeta.json file via a webhook (marked beta on the site), after which the record is edited and submitted; or email to the editor at [email protected].
Editors review submissions for completeness and suitability and may edit them. Registration is free.
Strengths and limits
- Discipline-specific discovery. A single list of astronomy and astrophysics codes tied to papers, indexed in ADS and Web of Science.
- Citable identifier at no fee. An
ascl:ID can be obtained without a fee and used when citing software. - Open and closed code both allowed. Public-domain status is not required.
- Limit: a registry, mostly. The ASCL points to code hosted elsewhere; an archive file is housed only when no download site exists.
- Limit: paper-linked entries. The submission requirements ask for a research paper that uses the code, so tools with no associated paper fall outside the stated requirements.
- Limit: not a DOI. Journals or funders that require a DOI for software need a different route (see the table).
Alternatives and complements
| Option | What it is | How it differs from the ASCL |
|---|---|---|
| ASCL | Free discipline registry for astronomy and astrophysics source codes | Issues ascl:yymm.xxx IDs; entries tied to a research paper; indexed in ADS and Web of Science |
| Zenodo | General-purpose repository operated by CERN | Mints a DataCite DOI for each deposit and can archive a tagged GitHub release; not specific to astronomy |
| JOSS and JORS | Journals that publish papers about research software | Peer-reviewed software papers rather than a code registry; they can be used together with a registry |
These are complements more than substitutes: a code can be registered in the ASCL for discovery by astronomers and archived in Zenodo for a DOI. For a similar discipline-specific versus general split among preprint servers, see the TechRxiv vs arXiv comparison.
FAQ
What does ASCL stand for?
Astrophysics Source Code Library. It is sometimes searched as “astrophysics source code library.”
Is the ASCL free?
Yes. ASCL staff describe it as free to use, with no fee to register a code.
Does my code have to be open source?
No. The Submissions page states that code does not have to be in the public domain for inclusion.
How do I cite an ASCL code?
Use the entry’s ascl:yymm.xxx identifier and the “Preferred citation method” shown on its record. The ID identifies the software; it is not a DOI.
Who is the ASCL for?
Astronomers and astrophysicists, including solar system astronomers, who write or use research code, and the authors who want that code to be discoverable and citable.
Sources
- Astrophysics Source Code Library, ascl.net, read 2026-11-08.
- ASCL, Submissions, read 2026-11-08.
- ASCL staff, Ten (or more!) reasons to register your software with the ASCL, arXiv:2412.19941, read 2026-11-08.
