Open source alternatives to Zapier

By GitHub stars it is Activepieces, with 25,513 stars and a commit on 13 Nov. Choose Activepieces when you want app-to-app flows running on your own server, free of per-task or per-credit billing. Next come Windmill (18,576 stars) and ByteChef (1,061 stars).

Yes. The code of all 3 is public under MIT, AGPL 3.0 or Apache 2.0, so you can use them with no licence fee. Running one yourself costs the server and your time to look after it, and some makers also sell a hosted plan.

Start from the job you use Zapier for. Choose ByteChef when you want workflows and agents running on your own servers so app data never passes through a SaaS. Choose Windmill when engineers want workflows written in code with retries and approvals, and unlimited runs when self-hosted.

All 3: Activepieces, Windmill and ByteChef. Each tool's page says what it needs to run.

All 3 we track had a commit in the last 30 days, among them Activepieces, Windmill and ByteChef. A recent commit shows the project is kept up, not that it will stay that way.

MIT (1), AGPL 3.0 (1), Apache 2.0 (1). MIT, BSD and Apache let you change and reuse the code freely. GPL and AGPL ask you to share your changes under the same licence when you give the software to others, and AGPL also counts letting people use it over a network.

The hosting. Zapier's maker runs the servers for you; with an open source tool the updates, backups, security fixes and support are yours, unless you take the maker's hosted plan. Features differ too, so check what each one imports and exports before you move your data.