Pull Request

Software consists of text files that many people work on at the same time. So that no one overwrites anyone else, there is an official version of the project. Anyone who wants to change something first works on their own copy. Once the change is finished, they open a pull request: a formal request to incorporate their own change into the official version. The pull request shows exactly which lines were added, deleted, or replaced. Other participants read it, ask questions, and in the end either approve or reject it.

Why it matters

The pull request is the central quality control mechanism in software development. No code enters a larger project without at least one other person having read it. This catches errors early, while they are still cheap to fix.

It also creates a kind of record. Every change is documented with justification, discussion, and approval. If something breaks a year later, you can look up who made which decision and why. In companies with traceability requirements, this is not just convenient but mandatory.

For open projects with volunteers contributing from all over the world, this procedure is the basic prerequisite. Strangers can submit proposals without needing write access to the original.

How it works

The process has five steps. First, the developer creates what is called a branch, i.e. a separate line of work alongside the official version. There she changes whatever she wants to change and saves the intermediate states. Then she opens the pull request and describes in words what the whole thing is supposed to achieve.

Now the review begins, known in technical jargon as code review. Colleagues read the change line by line and leave comments directly at the relevant spots. Usually the author then reworks the change and adds further changes within the same pull request. In parallel, automated tests run, checking whether the program still starts and computes without errors.

Once everyone is satisfied and the tests are green, the pull request is merged. This is called merging. The separate line of work fuses with the official version and is then deleted. The comparison to an editorial process fits well here: an author delivers a text, an editor marks passages, the author revises, and only then does it go to print.

Where you encounter the term

The expression comes from GitHub, the largest platform for collaborative software development. It hosts millions of open projects, and anyone can read the pull requests in their browser. At GitLab, a competitor, the same thing is called a merge request. It refers to the identical thing.

In technology news, pull requests often appear as evidence. When journalists write that a company is working on a new feature, they sometimes rely on publicly visible proposed changes in its code.

Currently, the picture is shifting due to AI. Programming assistants are now writing pull requests themselves and submitting them for review. At some companies, a significant portion of proposals no longer comes from humans. This is changing the work of developers: they write less themselves and review more instead. This is precisely why there is debate about how thoroughly humans still read machine-generated code at all.