Astrophysics Source Code Library

Making codes discoverable since 1999

Q & A

We can't claim all these questions are frequent, but they have come up, some of them in response to an AstroBetter post on the ASCL. (Last update: June 22, 2021)

Have a question that isn't answered here? Please email us or send a tweet our way (@asclnet); thanks!

Q: Why have the ASCL?
A: Research results are increasingly dependent on codes; as these codes are part of the methods of the research, science requires they, as with other methods, be open for examination. The ASCL seeks to make codes more easily accessible.

Q: Why should my code be listed in the ASCL?
A: Good science. Indexing by ADS. Making it easier for others to find your code. Your name in lights; the lights might just be pixels on a screen, but still: your name in lights. Making your code citable. Demonstrating your confidence in your research results and your ability to further science even if your results are ultimately not correct.

Q: Do codes have to be licensed a particular way to be listed in the ASCL?
: No. How a code is licensed has no bearing on whether it can be listed in the ASCL. Codes can be in the public domain, any open source (e.g., BSD, GPL), or copyrighted. It doesn't matter how a code is licensed; what matters is that a code used to generate results in research be open for examination.
Update on February 13, 2018: Licenses for ASCL codes on Github

Q: My code is cobbled together/messy/undocumented/lacks comments...
A: As are my office, desk, closets, dining room, and household budget spreadsheet. If someone's judging me on how cobbled together/messy/undocumented/uncommented my life is when examining the results I produce, they've missed the point, so long as the point of my results were not to tidy up/document/comment something. To paraphrase Nick Barnes, if a code is good enough to use in your research, it's good enough to make public, to let others look at it.

Q: Do you test the links to the code sites/how often do you test the links to the code sites?
A: We test the code links several times a week and report link health right at the top of our dashboard.

Q: How many codes does the ASCL have?
: A growing number, which you can see on our dashboard or on our Browse page.

Q: Who funds the ASCL?
A: The Heidelberg Institute for Theoretical Studies (HITS) provides funding to offset travel and other expenses, Michigan Technological University (MTU) hosts the ASCL and provides support and computer resources, and University of Maryland College Park provides office space and other support services, including library services. Those who work on the ASCL are volunteers. In 2012, the American Astronomical Society awarded seed money to the ASCL to help raise awareness of it at conferences and meetings. We're very thankful for the support we get!

Q: With the ADS indexing ASCL entries, are there going to be duplicate entries for each code submitted? If so, what is the citation methodology you see being the best — to encourage people to cite the ASCL, or to cite something like ApJS? (Adapted from AstroBetter comments 1 and 2.)
A: Yes, there will be duplicate entries for some codes.

Many codes do not have a “code paper” that describes the code; we seek to make codes citable even when they do not have such a paper.

Does the community need one consistent way of citing codes and if so, who's responsible for determining what that is? The ASCL provides one option; it’s not intended to compete with journals, however, but rather to complement them. The important thing is having a reliable way to let people know what was used, and how to find it, and it was the community that created a citation standard for ASCL entries.

Q. Some codes are in a continuous development cycle, and because they are open source and/or collaborative efforts, can no longer be viewed as credited only to the individuals who first created the codes; does that mean that the record, in both ADS and ASCL, should be updated with new information, wherein each contributor be listed? (Adapted from AstroBetter comments 2, 3, 4, and 7.)
. In some cases, an ASCL entry refers to the list of contributors on the download site rather than listing all contributors. We're open to suggestions as to how to better handle codes with an ongoing development cycle.

Q: Can you do quick statistics on the URLs for the codes? What fraction have:

1. no link to a repository
2. link to a major repository (, github, sourceforge)
3. link to a .edu website
4. link somewhere else
5. a broken link that you have been unable to recover?

The reason I ask is because for #2 there are APIs to the repositories that enable rich reuse of the meta-data about the code (version, authors, forks, last updated, issue tracking) perhaps even right in the ASCL entry. (Pulled right from AstroBetter comment 10.)
. We pulled quick stats in mid-February, 2012, and at that time, 28 codes showed up as on, bitbucket, github, or sourceforge, 121 on a .edu site, and the rest elsewhere. We had nearly 400 codes at the time, so that's over 60% on sites in the "link somewhere else" category.
(Stats as of February 9, 2014)
As of February 13, 2018, ~40% of the site links in the the ASCL are to,, and

For #5, broken links, we test the links regularly and report the results on our dashboard. We actively curate our entries, and when a link to a code site is reported as down over several weeks, we investigate it further and, when necessary and possible, replace the non-working link with a working one.

We think the right place for most of the metadata you list is on the code’s website rather than in the ASCL because that kind of metadata undergoes many changes. Our focus is on many codes perhaps thinly described rather than fewer codes richly described. Of course we'd love to have all codes richly described, but it’s a time thing: there just isn’t enough of it.

Q. If citation were to re-enforce any cultural behaviors I would hope it would be to put code in shared repositories and not just anywhere because you know someone might curate it someday. (Pulled right from AstroBetter comment 10.)
. The ASCL was originally strictly a repository. Requiring that code be stored on the site inhibited the ASCL's growth (as it did with other code repositories that have been established over the years). There are a number of reasons some coders don't, or can't, use resources such as SourceForge and Github. Many coders prefer to keep their codes close to them for a variety of reasons, including version control. Their university may restrict them from using a repository, the coder may not like the policies of available repositories, or may not want to maintain an online site. As shown in the numbers in the update to the previous answer, ~40% of codes in the ASCL are currently housed in one of the four listed shared repositories. Over time, that percentage has risen because of the growing popularity of collaborative coding, but unless publications require codes used in research to be in a shared repository, codes will continue to be housed in various environments.

The ASCL can act as a repository for those coders who do not want to maintain an online presence/download site for their code; the ASCL has always housed some codes. And we hope if a coder decides to abandon or orphan a code that has been used in research, the coder will put the code in a public repository or send us an archive file of the software so the method -- the code -- is preserved and the research which depended on the code is supported and reproducible. Please. We are happy to host codes for software authors who'd rather not, and assign DOIs for the codes we do house.

Q. Can I work on the ASCL?
A. Email us; we'll talk!