Cross-listing: when and how

Once you've chosen a primary categoryPrimary categoryThe single category that best fits a paper's main contribution. It decides which endorsement you need and where the paper is announced., arXiv lets you add secondary categoriesCategory (subject class)arXiv's topic label for a paper, such as cs.AI (Artificial Intelligence) or cs.CL (Computation and Language). Moderators and readers use it to route and find papers., known as cross-listsCross-listingAlso listing a paper in secondary categories so readers in related fields can find it. Use it only when the paper is genuinely relevant there.. A cross-list makes your paper appear in another category's listing too, so that a second community of readers can find it. Used well, cross-listing helps interdisciplinary work reach the right people. Used carelessly, it annoys readers and can be undone by moderatorsModerationarXiv's check of every submission for fit and basic quality before it is announced. It is separate from endorsement and from peer review..

ResearchGuild is independent and not affiliated with arXiv. The arXiv cross-listing page is the authoritative source.

What a cross-list does

According to arXiv, cross-listing to another category makes your article appear in the regular listing for that category, in the cross-list section. Your primary category doesn't change; it is still where the paper "lives". Cross-lists, like new submissions and replacements, are made public as part of arXiv's scheduled announcement process.

When a cross-list is a good idea

A cross-list is appropriate when a meaningful group of researchers in another category would genuinely want to read your paper. Some examples:

• An NLP paper (primary cs.CL) that introduces a training technique of broad interest to machine learning researchers might cross-list to cs.LG.
• A medical-imaging application paper whose primary is the application area might cross-list to cs.CV, which is what arXiv's machine learning classification guide suggests for that kind of paper.
• A statistics-focused ML paper with primary stat.ML is automatically cross-listed to cs.LG, per the same guide, so you don't need to add it yourself.

When it isn't

arXiv's guidance is direct:

• It is rarely appropriate to add more than one or two cross-lists.
• You are unlikely to know that a cross-list is appropriate unless you read that category yourself.
• Readers consider excessive or inappropriate cross-listing to be bad etiquette, so think about your cross-lists beforehand and don't cross-list without good reason.

A helpful test: have you read several recent papers in that category's listing, and would your paper look at home among them? If you've never browsed the category, that's a sign to leave it off.

Common temptations to resist:

• Adding cs.AI to every AI-flavoured paper "for visibility".
• Cross-listing to every field your application touches.
• Choosing categories based on which are busiest.

How moderators handle cross-lists

arXiv's moderation page says moderators may add cross-lists to related categories, or remove them when the classification is deemed inappropriate. Classification questions are also one of the reasons a submission can be placed on holdOn holdA submission status meaning arXiv moderators are taking a closer look before announcing the paper.. If a moderator removes a cross-list, that is a normal part of the process; see After you submit for what happens and how appeals work.

arXiv also asks authors not to contact moderators directly about their submissions. Questions go through arXiv's user support channels.

How to add a cross-list

• At submission time: you choose your primary category and can add cross-lists during the submission process.
• After announcement: arXiv's cross-listing page describes a cross-list facility on your user page for adding cross-lists to an existing article. The details of this interface can change, so follow the current instructions on that page.

Cross-lists and endorsement

EndorsementEndorsementA statement, made on arXiv's own form by an established arXiv author, that you are someone who can reasonably contribute to a subject area. It is not peer review and doesn't guarantee acceptance. is tied to where you submit. arXiv's endorsement page says you need endorsement before submitting your first paper or submitting to a new category. We have not found an official statement on whether cross-listing into a new domain requires separate endorsement; if this affects you, check arXiv's endorsement page or ask arXiv support.

A simple rule of thumb

Pick one primary. Add zero, one or at most two cross-lists that you, as a reader, would actually expect to see your paper in. If you're unsure, ask a reviewer on ResearchGuild who reads those listings; see Choosing your primary category for how to reason about audiences.