Best Self-Hosted Wikis and Knowledge Bases

A wiki is the tool teams buy last and give up on first. The failure is rarely the software: it is that nobody decided who the wiki is for before choosing it. A personal knowledge base wants linking and search; a team runbook wants structure and permissions; a Confluence migration wants spaces and diagrams. The four options here are good at genuinely different things, and the biggest difference between them is not features — it is licensing, which decides what you are allowed to do with the instance you built.

Which one should you pick?

Licensing is the deciding factor here, and it is the one nobody checks. BookStack is MIT and Docmost is AGPL-3.0 core, so both are OSI-approved open source and you can run them for any purpose. Wiki.js is AGPL-3.0 as well. Outline is not open source at all: it ships under the Business Source License 1.1, which its own text says is not an Open Source licence, and the use grant forbids offering it to third parties as a commercial document service. For an internal wiki that restriction will never bite. If you were planning to become a wiki host, it is disqualifying. After licensing, the axis is how much structure you want imposed on you: BookStack imposes a lot and is fast to adopt, Docmost gives you spaces, Wiki.js gives you modules, and Outline gives you the fastest editor of the four at the cost of the most operational work.

What actually decides it

• Check the licence before the feature list. Two of these four are open source without conditions and one carries a commercial-use restriction that matters if you ever expose the instance to people outside your organisation. Feature parity between them is close enough that licensing is often the only difference that persists.
• Count the containers honestly. BookStack and Wiki.js are comfortable as one application container plus a database. Docmost is three. Outline is four plus object storage. Every additional service is something you upgrade, back up and get paged about.
• Decide who writes, not who reads. A wiki with ten readers and one writer needs search and an obvious place to put things. A wiki with ten writers needs edit history, drafting and permissions. Most failed wikis were chosen for readers by people who were not going to be writers.
• Plan the migration exit on day one. You will change tools at least once. Prefer wikis with a documented export path to Markdown or HTML, and test that export in the first month rather than discovering its limits when you are trying to leave.