“Bug fixes and performance improvements.”
That line appears in changelogs everywhere: mobile apps, developer tools, SaaS products, open source libraries. It’s not technically wrong. It’s also not useful. For the user who noticed that their integration started behaving differently after an update, “bug fixes and performance improvements” means nothing. For the user wondering whether this release fixed the issue they filed three months ago, it’s a dead end. For the developer deciding whether to upgrade a dependency, it’s not enough information to make the decision.
A changelog is documentation. Not documentation for new users — documentation for existing ones. It’s the record of what changed, why it changed, and what you need to do about it. Existing users have a relationship with the product; the changelog is how you maintain that relationship across releases.
A useful changelog entry names the thing that changed. Not “improved authentication” — which authentication? Which endpoint, which parameter, which flow? If the entry affects something users touch directly, it should be specific enough that the affected user recognizes it immediately.
A useful changelog entry describes the impact. Did the change fix a bug that caused specific behavior in a specific situation? Say what the situation was. Did the change deprecate a parameter? Say which one and what to use instead. Did the change break anything that was previously working? Say what broke and how to fix it.
A useful changelog entry tells the user what to do. If no action is required, say so. If migration steps are needed, include them or link to them. If the change is only in internal plumbing and users won’t notice anything, that’s worth saying too.
keepachangelog.com defines a useful format that distinguishes between added, changed, deprecated, removed, fixed, and security changes in each release. It’s simple enough to adopt in any project and specific enough to communicate meaningfully. The format isn’t mandatory, but the underlying principle is: categorize changes by type so users can scan for what matters to them.
The changelog is also a historical record. Six months from now, when a user asks “when did you change the way authentication tokens expire?”, the changelog is how you answer. When a developer is debugging an integration and needs to know if something changed between version 2.3 and 2.4, the changelog is the reference. This makes the changelog useful well beyond the moment of release.
Writing a good changelog entry takes roughly the same amount of time as writing a bad one. The constraint is usually not effort but habit: teams that treat the changelog as an afterthought write afterthought changelog entries. Teams that treat it as part of the release process write changelog entries while they still have context — before the next feature absorbs all available attention.
Write it before you ship. The user on the other side is trying to understand what changed.