Why does everyone use github instead of just emailing each other code files?

Head of Product

The email-and-file-attachment model for sharing code breaks down in specific ways that become obvious quickly once more than one person is working on a codebase, and GitHub's value is best understood by working through exactly where it breaks. When code lives in files attached to emails, there is no authoritative version. If two people modify different copies of the same file and email their changes back, someone has to manually reconcile them, figuring out which lines conflict and what the combined correct version should be. That reconciliation process is error-prone, doesn't scale beyond a few collaborators, and produces no record of why any specific change was made or by whom. If something breaks after a change, finding out what changed and who changed it requires searching through emails and comparing file timestamps, which works poorly even for a two-person team. Git, the underlying version control system that GitHub is built on, solves the reconciliation problem through a structured merge process. Every change is tracked, attributed to a specific person, and accompanied by a message describing what was changed and why. When two people modify the same file in incompatible ways, Git surfaces the conflict explicitly and requires a human to resolve it deliberately, rather than silently overwriting one version with another. The entire history of every change to every file is preserved and searchable, so questions like "who changed this line and when" and "what was in this file six months ago" have reliable answers. GitHub adds collaboration infrastructure on top of Git. The pull request is the central unit: when someone wants to add their changes to the main codebase, they open a pull request that shows exactly what they changed, line by line. Other team members can review the changes, leave comments on specific lines, request modifications, and approve or reject the change before it's incorporated. That review process — asynchronous, documented, and tied to the specific code — is fundamentally different from emailing someone a file and asking if it looks okay. GitHub also provides issue tracking for bugs, features, and tasks that lives alongside the code, wikis for documentation, and a release management system for tracking what code is deployed where. All of this is searchable and tied together, so a team can trace a bug report to the specific change that introduced it and to the discussion that happened during its review. The network effect is also worth naming. GitHub is where the vast majority of open-source code is hosted, which means that when you use open-source libraries — and nearly every software project does — you're already interacting with GitHub. Having your own code on GitHub means your team is already familiar with the workflow, integrations with open-source tooling are straightforward, and external contributors can work with your codebase using the same tools they use everywhere else. For any team of more than one developer working on code that runs in production, the cost of not using version control compounds rapidly with team size and codebase complexity. GitHub is the most widely used platform for this workflow, which means tooling support, documentation, and hiring familiarity are all strongest there.