Open access

Open access is the practice of making research publications freely available to read online, without a subscription, paywall, or per-article fee for the reader.

"Gold" open access publishes directly in a journal that makes all its articles free, often funded by an author-paid publication fee, while "green" open access lets an author deposit a version of the paper, sometimes a preprint or accepted manuscript rather than the publisher's final formatted version, in a public repository alongside a paywalled publication. This differs from open data, which concerns the underlying research data rather than the published article describing it, a paper can be open access with closed data, or the reverse.

Open access matters for equitable access to research, particularly for readers outside well-funded institutions, and is increasingly required by funders and governments for publicly funded work; open access papers are also more readily surfaced by altmetrics tracking, and some citation analysis studies suggest they are cited somewhat more, though the size and causes of any advantage are debated. Pitfalls include the rise of "predatory" journals that charge open-access fees without genuine peer review, which has made publication venue reputation matter more, not less, and article-processing charges that can themselves create a new access barrier for authors at under-resourced institutions.